Add new skills for backend patterns, coding standards, continuous learning, and NestJS best practices
- Introduced backend patterns skill with guidelines on API design, database optimization, and server-side best practices. - Added coding standards skill outlining universal coding principles for TypeScript, NestJS, and Node.js development. - Implemented continuous learning skill to automatically extract reusable patterns from Cursor sessions. - Created NestJS best practices skill detailing architecture patterns, dependency injection, error handling, and security measures. - Included various rules and templates for NestJS best practices to ensure production-ready applications.
This commit is contained in:
shancheas
@@ -0,0 +1,564 @@
|
||||
---
|
||||
name: backend-patterns
|
||||
description: Backend architecture patterns, API design, database optimization, and server-side best practices for NestJS and Drizzle.
|
||||
---
|
||||
|
||||
# Backend Development Patterns
|
||||
|
||||
Backend architecture patterns and best practices for scalable NestJS applications.
|
||||
|
||||
## API Design Patterns
|
||||
|
||||
### RESTful API Structure
|
||||
|
||||
```typescript
|
||||
// ✅ Resource-based URLs
|
||||
GET /api/markets # List resources
|
||||
GET /api/markets/:id # Get single resource
|
||||
POST /api/markets # Create resource
|
||||
PUT /api/markets/:id # Replace resource
|
||||
PATCH /api/markets/:id # Update resource
|
||||
DELETE /api/markets/:id # Delete resource
|
||||
|
||||
// ✅ Query parameters for filtering, sorting, pagination
|
||||
GET /api/markets?status=active&sort=volume&limit=20&offset=0
|
||||
```
|
||||
|
||||
### Repository Pattern
|
||||
|
||||
```typescript
|
||||
// Abstract data access logic
|
||||
interface MarketRepository {
|
||||
findAll(filters?: MarketFilters): Promise<Market[]>
|
||||
findById(id: string): Promise<Market | null>
|
||||
create(data: CreateMarketDto): Promise<Market>
|
||||
update(id: string, data: UpdateMarketDto): Promise<Market>
|
||||
delete(id: string): Promise<void>
|
||||
}
|
||||
|
||||
class DrizzleMarketRepository implements MarketRepository {
|
||||
constructor(private readonly db: DrizzleDB) {}
|
||||
|
||||
async findAll(filters?: MarketFilters): Promise<Market[]> {
|
||||
let query = this.db.select().from(markets)
|
||||
|
||||
if (filters?.status) {
|
||||
query = query.where(eq(markets.status, filters.status)) as typeof query
|
||||
}
|
||||
|
||||
if (filters?.limit) {
|
||||
query = query.limit(filters.limit) as typeof query
|
||||
}
|
||||
|
||||
return query
|
||||
}
|
||||
|
||||
// Other methods...
|
||||
}
|
||||
```
|
||||
|
||||
### Service Layer Pattern
|
||||
|
||||
```typescript
|
||||
// Business logic separated from data access
|
||||
class MarketService {
|
||||
constructor(private marketRepo: MarketRepository) {}
|
||||
|
||||
async searchMarkets(query: string, limit: number = 10): Promise<Market[]> {
|
||||
// Business logic
|
||||
const embedding = await generateEmbedding(query)
|
||||
const results = await this.vectorSearch(embedding, limit)
|
||||
|
||||
// Fetch full data
|
||||
const markets = await this.marketRepo.findByIds(results.map(r => r.id))
|
||||
|
||||
// Sort by similarity
|
||||
return markets.sort((a, b) => {
|
||||
const scoreA = results.find(r => r.id === a.id)?.score || 0
|
||||
const scoreB = results.find(r => r.id === b.id)?.score || 0
|
||||
return scoreA - scoreB
|
||||
})
|
||||
}
|
||||
|
||||
private async vectorSearch(embedding: number[], limit: number) {
|
||||
// Vector search implementation
|
||||
}
|
||||
}
|
||||
```
|
||||
|
||||
### Middleware Pattern
|
||||
|
||||
```typescript
|
||||
// Request/response processing pipeline
|
||||
export function withAuth(handler: NextApiHandler): NextApiHandler {
|
||||
return async (req, res) => {
|
||||
const token = req.headers.authorization?.replace('Bearer ', '')
|
||||
|
||||
if (!token) {
|
||||
return res.status(401).json({ error: 'Unauthorized' })
|
||||
}
|
||||
|
||||
try {
|
||||
const user = await verifyToken(token)
|
||||
req.user = user
|
||||
return handler(req, res)
|
||||
} catch (error) {
|
||||
return res.status(401).json({ error: 'Invalid token' })
|
||||
}
|
||||
}
|
||||
}
|
||||
|
||||
// Usage
|
||||
export default withAuth(async (req, res) => {
|
||||
// Handler has access to req.user
|
||||
})
|
||||
```
|
||||
|
||||
## Database Patterns
|
||||
|
||||
### Query Optimization
|
||||
|
||||
```typescript
|
||||
// ✅ GOOD: Select only needed columns
|
||||
const data = await db
|
||||
.select({
|
||||
id: markets.id,
|
||||
name: markets.name,
|
||||
status: markets.status,
|
||||
volume: markets.volume,
|
||||
})
|
||||
.from(markets)
|
||||
.where(eq(markets.status, 'active'))
|
||||
.orderBy(desc(markets.volume))
|
||||
.limit(10)
|
||||
|
||||
// ❌ BAD: Select everything
|
||||
const data = await db.select().from(markets)
|
||||
```
|
||||
|
||||
### N+1 Query Prevention
|
||||
|
||||
```typescript
|
||||
// ❌ BAD: N+1 query problem
|
||||
const markets = await getMarkets()
|
||||
for (const market of markets) {
|
||||
market.creator = await getUser(market.creator_id) // N queries
|
||||
}
|
||||
|
||||
// ✅ GOOD: Batch fetch
|
||||
const markets = await getMarkets()
|
||||
const creatorIds = markets.map(m => m.creator_id)
|
||||
const creators = await getUsers(creatorIds) // 1 query
|
||||
const creatorMap = new Map(creators.map(c => [c.id, c]))
|
||||
|
||||
markets.forEach(market => {
|
||||
market.creator = creatorMap.get(market.creator_id)
|
||||
})
|
||||
```
|
||||
|
||||
### Transaction Pattern
|
||||
|
||||
```typescript
|
||||
async function createMarketWithPosition(
|
||||
marketData: CreateMarketDto,
|
||||
positionData: CreatePositionDto
|
||||
) {
|
||||
return db.transaction(async (tx) => {
|
||||
const [market] = await tx.insert(markets).values(marketData).returning()
|
||||
const [position] = await tx
|
||||
.insert(positions)
|
||||
.values({ ...positionData, marketId: market.id })
|
||||
.returning()
|
||||
return { market, position }
|
||||
})
|
||||
}
|
||||
```
|
||||
|
||||
## Caching Strategies
|
||||
|
||||
### Redis Caching Layer
|
||||
|
||||
```typescript
|
||||
class CachedMarketRepository implements MarketRepository {
|
||||
constructor(
|
||||
private baseRepo: MarketRepository,
|
||||
private redis: RedisClient
|
||||
) {}
|
||||
|
||||
async findById(id: string): Promise<Market | null> {
|
||||
// Check cache first
|
||||
const cached = await this.redis.get(`market:${id}`)
|
||||
|
||||
if (cached) {
|
||||
return JSON.parse(cached)
|
||||
}
|
||||
|
||||
// Cache miss - fetch from database
|
||||
const market = await this.baseRepo.findById(id)
|
||||
|
||||
if (market) {
|
||||
// Cache for 5 minutes
|
||||
await this.redis.setex(`market:${id}`, 300, JSON.stringify(market))
|
||||
}
|
||||
|
||||
return market
|
||||
}
|
||||
|
||||
async invalidateCache(id: string): Promise<void> {
|
||||
await this.redis.del(`market:${id}`)
|
||||
}
|
||||
}
|
||||
```
|
||||
|
||||
### Cache-Aside Pattern
|
||||
|
||||
```typescript
|
||||
async function getMarketWithCache(id: string): Promise<Market> {
|
||||
const cacheKey = `market:${id}`
|
||||
|
||||
// Try cache
|
||||
const cached = await redis.get(cacheKey)
|
||||
if (cached) return JSON.parse(cached)
|
||||
|
||||
// Cache miss - fetch from DB
|
||||
const market = await db.markets.findUnique({ where: { id } })
|
||||
|
||||
if (!market) throw new Error('Market not found')
|
||||
|
||||
// Update cache
|
||||
await redis.setex(cacheKey, 300, JSON.stringify(market))
|
||||
|
||||
return market
|
||||
}
|
||||
```
|
||||
|
||||
## Error Handling Patterns
|
||||
|
||||
### Centralized Error Handler
|
||||
|
||||
```typescript
|
||||
class ApiError extends Error {
|
||||
constructor(
|
||||
public statusCode: number,
|
||||
public message: string,
|
||||
public isOperational = true
|
||||
) {
|
||||
super(message)
|
||||
Object.setPrototypeOf(this, ApiError.prototype)
|
||||
}
|
||||
}
|
||||
|
||||
export function errorHandler(error: unknown, req: Request): Response {
|
||||
if (error instanceof ApiError) {
|
||||
return NextResponse.json({
|
||||
success: false,
|
||||
error: error.message
|
||||
}, { status: error.statusCode })
|
||||
}
|
||||
|
||||
if (error instanceof z.ZodError) {
|
||||
return NextResponse.json({
|
||||
success: false,
|
||||
error: 'Validation failed',
|
||||
details: error.errors
|
||||
}, { status: 400 })
|
||||
}
|
||||
|
||||
// Log unexpected errors
|
||||
console.error('Unexpected error:', error)
|
||||
|
||||
return NextResponse.json({
|
||||
success: false,
|
||||
error: 'Internal server error'
|
||||
}, { status: 500 })
|
||||
}
|
||||
|
||||
// Usage
|
||||
export async function GET(request: Request) {
|
||||
try {
|
||||
const data = await fetchData()
|
||||
return NextResponse.json({ success: true, data })
|
||||
} catch (error) {
|
||||
return errorHandler(error, request)
|
||||
}
|
||||
}
|
||||
```
|
||||
|
||||
### Retry with Exponential Backoff
|
||||
|
||||
```typescript
|
||||
async function fetchWithRetry<T>(
|
||||
fn: () => Promise<T>,
|
||||
maxRetries = 3
|
||||
): Promise<T> {
|
||||
let lastError: Error
|
||||
|
||||
for (let i = 0; i < maxRetries; i++) {
|
||||
try {
|
||||
return await fn()
|
||||
} catch (error) {
|
||||
lastError = error as Error
|
||||
|
||||
if (i < maxRetries - 1) {
|
||||
// Exponential backoff: 1s, 2s, 4s
|
||||
const delay = Math.pow(2, i) * 1000
|
||||
await new Promise(resolve => setTimeout(resolve, delay))
|
||||
}
|
||||
}
|
||||
}
|
||||
|
||||
throw lastError!
|
||||
}
|
||||
|
||||
// Usage
|
||||
const data = await fetchWithRetry(() => fetchFromAPI())
|
||||
```
|
||||
|
||||
## Authentication & Authorization
|
||||
|
||||
### JWT Token Validation
|
||||
|
||||
```typescript
|
||||
import jwt from 'jsonwebtoken'
|
||||
|
||||
interface JWTPayload {
|
||||
userId: string
|
||||
email: string
|
||||
role: 'admin' | 'user'
|
||||
}
|
||||
|
||||
export function verifyToken(token: string): JWTPayload {
|
||||
try {
|
||||
const payload = jwt.verify(token, process.env.JWT_SECRET!) as JWTPayload
|
||||
return payload
|
||||
} catch (error) {
|
||||
throw new ApiError(401, 'Invalid token')
|
||||
}
|
||||
}
|
||||
|
||||
export async function requireAuth(request: Request) {
|
||||
const token = request.headers.get('authorization')?.replace('Bearer ', '')
|
||||
|
||||
if (!token) {
|
||||
throw new ApiError(401, 'Missing authorization token')
|
||||
}
|
||||
|
||||
return verifyToken(token)
|
||||
}
|
||||
|
||||
// Usage in API route
|
||||
export async function GET(request: Request) {
|
||||
const user = await requireAuth(request)
|
||||
|
||||
const data = await getDataForUser(user.userId)
|
||||
|
||||
return NextResponse.json({ success: true, data })
|
||||
}
|
||||
```
|
||||
|
||||
### Role-Based Access Control
|
||||
|
||||
```typescript
|
||||
type Permission = 'read' | 'write' | 'delete' | 'admin'
|
||||
|
||||
interface User {
|
||||
id: string
|
||||
role: 'admin' | 'moderator' | 'user'
|
||||
}
|
||||
|
||||
const rolePermissions: Record<User['role'], Permission[]> = {
|
||||
admin: ['read', 'write', 'delete', 'admin'],
|
||||
moderator: ['read', 'write', 'delete'],
|
||||
user: ['read', 'write']
|
||||
}
|
||||
|
||||
export function hasPermission(user: User, permission: Permission): boolean {
|
||||
return rolePermissions[user.role].includes(permission)
|
||||
}
|
||||
|
||||
export function requirePermission(permission: Permission) {
|
||||
return async (request: Request) => {
|
||||
const user = await requireAuth(request)
|
||||
|
||||
if (!hasPermission(user, permission)) {
|
||||
throw new ApiError(403, 'Insufficient permissions')
|
||||
}
|
||||
|
||||
return user
|
||||
}
|
||||
}
|
||||
|
||||
// Usage
|
||||
export const DELETE = requirePermission('delete')(async (request: Request) => {
|
||||
// Handler with permission check
|
||||
})
|
||||
```
|
||||
|
||||
## Rate Limiting
|
||||
|
||||
### Simple In-Memory Rate Limiter
|
||||
|
||||
```typescript
|
||||
class RateLimiter {
|
||||
private requests = new Map<string, number[]>()
|
||||
|
||||
async checkLimit(
|
||||
identifier: string,
|
||||
maxRequests: number,
|
||||
windowMs: number
|
||||
): Promise<boolean> {
|
||||
const now = Date.now()
|
||||
const requests = this.requests.get(identifier) || []
|
||||
|
||||
// Remove old requests outside window
|
||||
const recentRequests = requests.filter(time => now - time < windowMs)
|
||||
|
||||
if (recentRequests.length >= maxRequests) {
|
||||
return false // Rate limit exceeded
|
||||
}
|
||||
|
||||
// Add current request
|
||||
recentRequests.push(now)
|
||||
this.requests.set(identifier, recentRequests)
|
||||
|
||||
return true
|
||||
}
|
||||
}
|
||||
|
||||
const limiter = new RateLimiter()
|
||||
|
||||
export async function GET(request: Request) {
|
||||
const ip = request.headers.get('x-forwarded-for') || 'unknown'
|
||||
|
||||
const allowed = await limiter.checkLimit(ip, 100, 60000) // 100 req/min
|
||||
|
||||
if (!allowed) {
|
||||
return NextResponse.json({
|
||||
error: 'Rate limit exceeded'
|
||||
}, { status: 429 })
|
||||
}
|
||||
|
||||
// Continue with request
|
||||
}
|
||||
```
|
||||
|
||||
## Background Jobs & Queues
|
||||
|
||||
### Simple Queue Pattern
|
||||
|
||||
```typescript
|
||||
class JobQueue<T> {
|
||||
private queue: T[] = []
|
||||
private processing = false
|
||||
|
||||
async add(job: T): Promise<void> {
|
||||
this.queue.push(job)
|
||||
|
||||
if (!this.processing) {
|
||||
this.process()
|
||||
}
|
||||
}
|
||||
|
||||
private async process(): Promise<void> {
|
||||
this.processing = true
|
||||
|
||||
while (this.queue.length > 0) {
|
||||
const job = this.queue.shift()!
|
||||
|
||||
try {
|
||||
await this.execute(job)
|
||||
} catch (error) {
|
||||
console.error('Job failed:', error)
|
||||
}
|
||||
}
|
||||
|
||||
this.processing = false
|
||||
}
|
||||
|
||||
private async execute(job: T): Promise<void> {
|
||||
// Job execution logic
|
||||
}
|
||||
}
|
||||
|
||||
// Usage for indexing markets
|
||||
interface IndexJob {
|
||||
marketId: string
|
||||
}
|
||||
|
||||
const indexQueue = new JobQueue<IndexJob>()
|
||||
|
||||
export async function POST(request: Request) {
|
||||
const { marketId } = await request.json()
|
||||
|
||||
// Add to queue instead of blocking
|
||||
await indexQueue.add({ marketId })
|
||||
|
||||
return NextResponse.json({ success: true, message: 'Job queued' })
|
||||
}
|
||||
```
|
||||
|
||||
## Logging & Monitoring
|
||||
|
||||
### Structured Logging
|
||||
|
||||
```typescript
|
||||
interface LogContext {
|
||||
userId?: string
|
||||
requestId?: string
|
||||
method?: string
|
||||
path?: string
|
||||
[key: string]: unknown
|
||||
}
|
||||
|
||||
class Logger {
|
||||
log(level: 'info' | 'warn' | 'error', message: string, context?: LogContext) {
|
||||
const entry = {
|
||||
timestamp: new Date().toISOString(),
|
||||
level,
|
||||
message,
|
||||
...context
|
||||
}
|
||||
|
||||
console.log(JSON.stringify(entry))
|
||||
}
|
||||
|
||||
info(message: string, context?: LogContext) {
|
||||
this.log('info', message, context)
|
||||
}
|
||||
|
||||
warn(message: string, context?: LogContext) {
|
||||
this.log('warn', message, context)
|
||||
}
|
||||
|
||||
error(message: string, error: Error, context?: LogContext) {
|
||||
this.log('error', message, {
|
||||
...context,
|
||||
error: error.message,
|
||||
stack: error.stack
|
||||
})
|
||||
}
|
||||
}
|
||||
|
||||
const logger = new Logger()
|
||||
|
||||
// Usage
|
||||
export async function GET(request: Request) {
|
||||
const requestId = crypto.randomUUID()
|
||||
|
||||
logger.info('Fetching markets', {
|
||||
requestId,
|
||||
method: 'GET',
|
||||
path: '/api/markets'
|
||||
})
|
||||
|
||||
try {
|
||||
const markets = await fetchMarkets()
|
||||
return NextResponse.json({ success: true, data: markets })
|
||||
} catch (error) {
|
||||
logger.error('Failed to fetch markets', error as Error, { requestId })
|
||||
return NextResponse.json({ error: 'Internal error' }, { status: 500 })
|
||||
}
|
||||
}
|
||||
```
|
||||
|
||||
**Remember**: Backend patterns enable scalable, maintainable server-side applications. Choose patterns that fit your complexity level.
|
||||
@@ -0,0 +1,503 @@
|
||||
---
|
||||
name: coding-standards
|
||||
description: Universal coding standards, best practices, and patterns for TypeScript, NestJS, and Node.js development.
|
||||
---
|
||||
|
||||
# Coding Standards & Best Practices
|
||||
|
||||
Universal coding standards applicable across all projects.
|
||||
|
||||
## Code Quality Principles
|
||||
|
||||
### 1. Readability First
|
||||
- Code is read more than written
|
||||
- Clear variable and function names
|
||||
- Self-documenting code preferred over comments
|
||||
- Consistent formatting
|
||||
|
||||
### 2. KISS (Keep It Simple, Stupid)
|
||||
- Simplest solution that works
|
||||
- Avoid over-engineering
|
||||
- No premature optimization
|
||||
- Easy to understand > clever code
|
||||
|
||||
### 3. DRY (Don't Repeat Yourself)
|
||||
- Extract common logic into functions
|
||||
- Create reusable components
|
||||
- Share utilities across modules
|
||||
- Avoid copy-paste programming
|
||||
|
||||
### 4. YAGNI (You Aren't Gonna Need It)
|
||||
- Don't build features before they're needed
|
||||
- Avoid speculative generality
|
||||
- Add complexity only when required
|
||||
- Start simple, refactor when needed
|
||||
|
||||
## TypeScript/JavaScript Standards
|
||||
|
||||
### Variable Naming
|
||||
|
||||
```typescript
|
||||
// ✅ GOOD: Descriptive names
|
||||
const marketSearchQuery = 'election'
|
||||
const isUserAuthenticated = true
|
||||
const totalRevenue = 1000
|
||||
|
||||
// ❌ BAD: Unclear names
|
||||
const q = 'election'
|
||||
const flag = true
|
||||
const x = 1000
|
||||
```
|
||||
|
||||
### Function Naming
|
||||
|
||||
```typescript
|
||||
// ✅ GOOD: Verb-noun pattern
|
||||
async function fetchMarketData(marketId: string) { }
|
||||
function calculateSimilarity(a: number[], b: number[]) { }
|
||||
function isValidEmail(email: string): boolean { }
|
||||
|
||||
// ❌ BAD: Unclear or noun-only
|
||||
async function market(id: string) { }
|
||||
function similarity(a, b) { }
|
||||
function email(e) { }
|
||||
```
|
||||
|
||||
### Immutability Pattern (CRITICAL)
|
||||
|
||||
```typescript
|
||||
// ✅ ALWAYS use spread operator
|
||||
const updatedUser = {
|
||||
...user,
|
||||
name: 'New Name'
|
||||
}
|
||||
|
||||
const updatedArray = [...items, newItem]
|
||||
|
||||
// ❌ NEVER mutate directly
|
||||
user.name = 'New Name' // BAD
|
||||
items.push(newItem) // BAD
|
||||
```
|
||||
|
||||
### Error Handling
|
||||
|
||||
```typescript
|
||||
// ✅ GOOD: Comprehensive error handling
|
||||
async function fetchData(url: string) {
|
||||
try {
|
||||
const response = await fetch(url)
|
||||
|
||||
if (!response.ok) {
|
||||
throw new Error(`HTTP ${response.status}: ${response.statusText}`)
|
||||
}
|
||||
|
||||
return await response.json()
|
||||
} catch (error) {
|
||||
console.error('Fetch failed:', error)
|
||||
throw new Error('Failed to fetch data')
|
||||
}
|
||||
}
|
||||
|
||||
// ❌ BAD: No error handling
|
||||
async function fetchData(url) {
|
||||
const response = await fetch(url)
|
||||
return response.json()
|
||||
}
|
||||
```
|
||||
|
||||
### Async/Await Best Practices
|
||||
|
||||
```typescript
|
||||
// ✅ GOOD: Parallel execution when possible
|
||||
const [users, markets, stats] = await Promise.all([
|
||||
fetchUsers(),
|
||||
fetchMarkets(),
|
||||
fetchStats()
|
||||
])
|
||||
|
||||
// ❌ BAD: Sequential when unnecessary
|
||||
const users = await fetchUsers()
|
||||
const markets = await fetchMarkets()
|
||||
const stats = await fetchStats()
|
||||
```
|
||||
|
||||
### Type Safety
|
||||
|
||||
```typescript
|
||||
// ✅ GOOD: Proper types
|
||||
interface Market {
|
||||
id: string
|
||||
name: string
|
||||
status: 'active' | 'resolved' | 'closed'
|
||||
created_at: Date
|
||||
}
|
||||
|
||||
function getMarket(id: string): Promise<Market> {
|
||||
// Implementation
|
||||
}
|
||||
|
||||
// ❌ BAD: Using 'any'
|
||||
function getMarket(id: any): Promise<any> {
|
||||
// Implementation
|
||||
}
|
||||
```
|
||||
|
||||
## React Best Practices
|
||||
|
||||
### Component Structure
|
||||
|
||||
```typescript
|
||||
// ✅ GOOD: Functional component with types
|
||||
interface ButtonProps {
|
||||
children: React.ReactNode
|
||||
onClick: () => void
|
||||
disabled?: boolean
|
||||
variant?: 'primary' | 'secondary'
|
||||
}
|
||||
|
||||
export function Button({
|
||||
children,
|
||||
onClick,
|
||||
disabled = false,
|
||||
variant = 'primary'
|
||||
}: ButtonProps) {
|
||||
return (
|
||||
<button
|
||||
onClick={onClick}
|
||||
disabled={disabled}
|
||||
className={`btn btn-${variant}`}
|
||||
>
|
||||
{children}
|
||||
</button>
|
||||
)
|
||||
}
|
||||
|
||||
// ❌ BAD: No types, unclear structure
|
||||
export function Button(props) {
|
||||
return <button onClick={props.onClick}>{props.children}</button>
|
||||
}
|
||||
```
|
||||
|
||||
### Custom Hooks
|
||||
|
||||
```typescript
|
||||
// ✅ GOOD: Reusable custom hook
|
||||
export function useDebounce<T>(value: T, delay: number): T {
|
||||
const [debouncedValue, setDebouncedValue] = useState<T>(value)
|
||||
|
||||
useEffect(() => {
|
||||
const handler = setTimeout(() => {
|
||||
setDebouncedValue(value)
|
||||
}, delay)
|
||||
|
||||
return () => clearTimeout(handler)
|
||||
}, [value, delay])
|
||||
|
||||
return debouncedValue
|
||||
}
|
||||
|
||||
// Usage
|
||||
const debouncedQuery = useDebounce(searchQuery, 500)
|
||||
```
|
||||
|
||||
### State Management
|
||||
|
||||
```typescript
|
||||
// ✅ GOOD: Proper state updates
|
||||
const [count, setCount] = useState(0)
|
||||
|
||||
// Functional update for state based on previous state
|
||||
setCount(prev => prev + 1)
|
||||
|
||||
// ❌ BAD: Direct state reference
|
||||
setCount(count + 1) // Can be stale in async scenarios
|
||||
```
|
||||
|
||||
### Conditional Rendering
|
||||
|
||||
```typescript
|
||||
// ✅ GOOD: Clear conditional rendering
|
||||
{isLoading && <Spinner />}
|
||||
{error && <ErrorMessage error={error} />}
|
||||
{data && <DataDisplay data={data} />}
|
||||
|
||||
// ❌ BAD: Ternary hell
|
||||
{isLoading ? <Spinner /> : error ? <ErrorMessage error={error} /> : data ? <DataDisplay data={data} /> : null}
|
||||
```
|
||||
|
||||
## API Design Standards
|
||||
|
||||
### REST API Conventions
|
||||
|
||||
```
|
||||
GET /api/markets # List all markets
|
||||
GET /api/markets/:id # Get specific market
|
||||
POST /api/markets # Create new market
|
||||
PUT /api/markets/:id # Update market (full)
|
||||
PATCH /api/markets/:id # Update market (partial)
|
||||
DELETE /api/markets/:id # Delete market
|
||||
|
||||
# Query parameters for filtering
|
||||
GET /api/markets?status=active&limit=10&offset=0
|
||||
```
|
||||
|
||||
### Response Format
|
||||
|
||||
```typescript
|
||||
// ✅ GOOD: Consistent response structure
|
||||
interface ApiResponse<T> {
|
||||
success: boolean
|
||||
data?: T
|
||||
error?: string
|
||||
meta?: {
|
||||
total: number
|
||||
page: number
|
||||
limit: number
|
||||
}
|
||||
}
|
||||
|
||||
// Success response
|
||||
return { success: true, data: markets, meta: { total: 100, page: 1, limit: 10 } }
|
||||
|
||||
// Error response
|
||||
throw new BadRequestException('Invalid request')
|
||||
}, { status: 400 })
|
||||
```
|
||||
|
||||
### Input Validation
|
||||
|
||||
```typescript
|
||||
import { IsString, MinLength, IsDateString, IsArray } from 'class-validator'
|
||||
|
||||
export class CreateMarketDto {
|
||||
@IsString()
|
||||
@MinLength(1)
|
||||
name: string
|
||||
|
||||
@IsString()
|
||||
@MinLength(1)
|
||||
description: string
|
||||
|
||||
@IsDateString()
|
||||
endDate: string
|
||||
|
||||
@IsArray()
|
||||
@IsString({ each: true })
|
||||
categories: string[]
|
||||
}
|
||||
|
||||
@Post()
|
||||
create(@Body() dto: CreateMarketDto) {
|
||||
return this.marketsService.create(dto)
|
||||
}
|
||||
```
|
||||
|
||||
## File Organization
|
||||
|
||||
### Project Structure
|
||||
|
||||
```
|
||||
src/
|
||||
├── main.ts
|
||||
├── app.module.ts
|
||||
├── common/ # Filters, guards, pipes, interceptors
|
||||
├── config/ # Env and Drizzle config
|
||||
└── modules/ # Feature modules
|
||||
├── auth/
|
||||
└── users/
|
||||
```
|
||||
|
||||
### File Naming
|
||||
|
||||
```
|
||||
components/Button.ts # PascalCase for classes
|
||||
modules/auth/auth.service.ts # NestJS feature files
|
||||
lib/format-date.ts # kebab/camelCase for utilities
|
||||
types/market.types.ts # camelCase with .types suffix
|
||||
```
|
||||
|
||||
## Comments & Documentation
|
||||
|
||||
### When to Comment
|
||||
|
||||
```typescript
|
||||
// ✅ GOOD: Explain WHY, not WHAT
|
||||
// Use exponential backoff to avoid overwhelming the API during outages
|
||||
const delay = Math.min(1000 * Math.pow(2, retryCount), 30000)
|
||||
|
||||
// Deliberately using mutation here for performance with large arrays
|
||||
items.push(newItem)
|
||||
|
||||
// ❌ BAD: Stating the obvious
|
||||
// Increment counter by 1
|
||||
count++
|
||||
|
||||
// Set name to user's name
|
||||
name = user.name
|
||||
```
|
||||
|
||||
### JSDoc for Public APIs
|
||||
|
||||
```typescript
|
||||
/**
|
||||
* Searches markets using semantic similarity.
|
||||
*
|
||||
* @param query - Natural language search query
|
||||
* @param limit - Maximum number of results (default: 10)
|
||||
* @returns Array of markets sorted by similarity score
|
||||
* @throws {Error} If OpenAI API fails or Redis unavailable
|
||||
*
|
||||
* @example
|
||||
* ```typescript
|
||||
* const results = await searchMarkets('election', 5)
|
||||
* console.log(results[0].name) // "Trump vs Biden"
|
||||
* ```
|
||||
*/
|
||||
export async function searchMarkets(
|
||||
query: string,
|
||||
limit: number = 10
|
||||
): Promise<Market[]> {
|
||||
// Implementation
|
||||
}
|
||||
```
|
||||
|
||||
## Performance Best Practices
|
||||
|
||||
### Memoization
|
||||
|
||||
```typescript
|
||||
import { useMemo, useCallback } from 'react'
|
||||
|
||||
// ✅ GOOD: Memoize expensive computations
|
||||
const sortedMarkets = useMemo(() => {
|
||||
return markets.sort((a, b) => b.volume - a.volume)
|
||||
}, [markets])
|
||||
|
||||
// ✅ GOOD: Memoize callbacks
|
||||
const handleSearch = useCallback((query: string) => {
|
||||
setSearchQuery(query)
|
||||
}, [])
|
||||
```
|
||||
|
||||
### Lazy Loading
|
||||
|
||||
```typescript
|
||||
import { lazy, Suspense } from 'react'
|
||||
|
||||
// ✅ GOOD: Lazy load heavy components
|
||||
const HeavyChart = lazy(() => import('./HeavyChart'))
|
||||
|
||||
export function Dashboard() {
|
||||
return (
|
||||
<Suspense fallback={<Spinner />}>
|
||||
<HeavyChart />
|
||||
</Suspense>
|
||||
)
|
||||
}
|
||||
```
|
||||
|
||||
### Database Queries
|
||||
|
||||
```typescript
|
||||
// ✅ GOOD: Select only needed columns
|
||||
const { data } = await supabase
|
||||
.from('markets')
|
||||
.select('id, name, status')
|
||||
.limit(10)
|
||||
|
||||
// ❌ BAD: Select everything
|
||||
const { data } = await supabase
|
||||
.from('markets')
|
||||
.select('*')
|
||||
```
|
||||
|
||||
## Testing Standards
|
||||
|
||||
### Test Structure (AAA Pattern)
|
||||
|
||||
```typescript
|
||||
test('calculates similarity correctly', () => {
|
||||
// Arrange
|
||||
const vector1 = [1, 0, 0]
|
||||
const vector2 = [0, 1, 0]
|
||||
|
||||
// Act
|
||||
const similarity = calculateCosineSimilarity(vector1, vector2)
|
||||
|
||||
// Assert
|
||||
expect(similarity).toBe(0)
|
||||
})
|
||||
```
|
||||
|
||||
### Test Naming
|
||||
|
||||
```typescript
|
||||
// ✅ GOOD: Descriptive test names
|
||||
test('returns empty array when no markets match query', () => { })
|
||||
test('throws error when OpenAI API key is missing', () => { })
|
||||
test('falls back to substring search when Redis unavailable', () => { })
|
||||
|
||||
// ❌ BAD: Vague test names
|
||||
test('works', () => { })
|
||||
test('test search', () => { })
|
||||
```
|
||||
|
||||
## Code Smell Detection
|
||||
|
||||
Watch for these anti-patterns:
|
||||
|
||||
### 1. Long Functions
|
||||
```typescript
|
||||
// ❌ BAD: Function > 50 lines
|
||||
function processMarketData() {
|
||||
// 100 lines of code
|
||||
}
|
||||
|
||||
// ✅ GOOD: Split into smaller functions
|
||||
function processMarketData() {
|
||||
const validated = validateData()
|
||||
const transformed = transformData(validated)
|
||||
return saveData(transformed)
|
||||
}
|
||||
```
|
||||
|
||||
### 2. Deep Nesting
|
||||
```typescript
|
||||
// ❌ BAD: 5+ levels of nesting
|
||||
if (user) {
|
||||
if (user.isAdmin) {
|
||||
if (market) {
|
||||
if (market.isActive) {
|
||||
if (hasPermission) {
|
||||
// Do something
|
||||
}
|
||||
}
|
||||
}
|
||||
}
|
||||
}
|
||||
|
||||
// ✅ GOOD: Early returns
|
||||
if (!user) return
|
||||
if (!user.isAdmin) return
|
||||
if (!market) return
|
||||
if (!market.isActive) return
|
||||
if (!hasPermission) return
|
||||
|
||||
// Do something
|
||||
```
|
||||
|
||||
### 3. Magic Numbers
|
||||
```typescript
|
||||
// ❌ BAD: Unexplained numbers
|
||||
if (retryCount > 3) { }
|
||||
setTimeout(callback, 500)
|
||||
|
||||
// ✅ GOOD: Named constants
|
||||
const MAX_RETRIES = 3
|
||||
const DEBOUNCE_DELAY_MS = 500
|
||||
|
||||
if (retryCount > MAX_RETRIES) { }
|
||||
setTimeout(callback, DEBOUNCE_DELAY_MS)
|
||||
```
|
||||
|
||||
**Remember**: Code quality is not negotiable. Clear, maintainable code enables rapid development and confident refactoring.
|
||||
@@ -0,0 +1,79 @@
|
||||
---
|
||||
name: continuous-learning
|
||||
description: Automatically extract reusable patterns from Cursor sessions and save them as learned skills for future use.
|
||||
---
|
||||
|
||||
# Continuous Learning Skill
|
||||
|
||||
Automatically evaluates Cursor sessions on end to extract reusable patterns that can be saved as learned skills.
|
||||
|
||||
## How It Works
|
||||
|
||||
This skill runs as a **sessionEnd hook** at the end of each session:
|
||||
|
||||
1. **Session Evaluation**: Checks if session has enough messages (default: 10+)
|
||||
2. **Pattern Detection**: Identifies extractable patterns from the session
|
||||
3. **Skill Extraction**: Saves useful patterns to `.agents/skills/learned/`
|
||||
|
||||
## Configuration
|
||||
|
||||
Edit `config.json` to customize:
|
||||
|
||||
```json
|
||||
{
|
||||
"min_session_length": 10,
|
||||
"extraction_threshold": "medium",
|
||||
"auto_approve": false,
|
||||
"learned_skills_path": ".agents/skills/learned/",
|
||||
"patterns_to_detect": [
|
||||
"error_resolution",
|
||||
"user_corrections",
|
||||
"workarounds",
|
||||
"debugging_techniques",
|
||||
"project_specific"
|
||||
],
|
||||
"ignore_patterns": [
|
||||
"simple_typos",
|
||||
"one_time_fixes",
|
||||
"external_api_issues"
|
||||
]
|
||||
}
|
||||
```
|
||||
|
||||
## Pattern Types
|
||||
|
||||
| Pattern | Description |
|
||||
|---------|-------------|
|
||||
| `error_resolution` | How specific errors were resolved |
|
||||
| `user_corrections` | Patterns from user corrections |
|
||||
| `workarounds` | Solutions to framework/library quirks |
|
||||
| `debugging_techniques` | Effective debugging approaches |
|
||||
| `project_specific` | Project-specific conventions |
|
||||
|
||||
## Hook Setup
|
||||
|
||||
Already wired in `.cursor/hooks.json` as a `sessionEnd` command:
|
||||
|
||||
```json
|
||||
{
|
||||
"version": 1,
|
||||
"hooks": {
|
||||
"sessionEnd": [
|
||||
{
|
||||
"command": "node .cursor/scripts/hooks/evaluate-session.js"
|
||||
}
|
||||
]
|
||||
}
|
||||
}
|
||||
```
|
||||
|
||||
## Why Stop Hook?
|
||||
|
||||
- **Lightweight**: Runs once at session end
|
||||
- **Non-blocking**: Doesn't add latency to every message
|
||||
- **Complete context**: Has access to full session transcript
|
||||
|
||||
## Related
|
||||
|
||||
- [The Longform Guide](https://x.com/affaanmustafa/status/2014040193557471352) - Section on continuous learning
|
||||
- `/learn` command - Manual pattern extraction mid-session
|
||||
@@ -0,0 +1,18 @@
|
||||
{
|
||||
"min_session_length": 10,
|
||||
"extraction_threshold": "medium",
|
||||
"auto_approve": false,
|
||||
"learned_skills_path": ".agents/skills/learned/",
|
||||
"patterns_to_detect": [
|
||||
"error_resolution",
|
||||
"user_corrections",
|
||||
"workarounds",
|
||||
"debugging_techniques",
|
||||
"project_specific"
|
||||
],
|
||||
"ignore_patterns": [
|
||||
"simple_typos",
|
||||
"one_time_fixes",
|
||||
"external_api_issues"
|
||||
]
|
||||
}
|
||||
+53
@@ -0,0 +1,53 @@
|
||||
#!/bin/bash
|
||||
# Continuous Learning - Session Evaluator
|
||||
# Runs on sessionEnd to extract reusable patterns from Cursor sessions
|
||||
#
|
||||
# Configured in .cursor/hooks.json:
|
||||
# sessionEnd -> node .cursor/scripts/hooks/evaluate-session.js
|
||||
# This shell version is a fallback.
|
||||
#
|
||||
# Extracted skills saved to: .agents/skills/learned/
|
||||
|
||||
set -e
|
||||
|
||||
SCRIPT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
|
||||
ROOT="$(git rev-parse --show-toplevel 2>/dev/null || pwd)"
|
||||
CONFIG_FILE="$SCRIPT_DIR/config.json"
|
||||
LEARNED_SKILLS_PATH="${ROOT}/.agents/skills/learned"
|
||||
MIN_SESSION_LENGTH=10
|
||||
|
||||
# Load config if exists
|
||||
if [ -f "$CONFIG_FILE" ]; then
|
||||
MIN_SESSION_LENGTH=$(jq -r '.min_session_length // 10' "$CONFIG_FILE")
|
||||
configured_path=$(jq -r '.learned_skills_path // empty' "$CONFIG_FILE")
|
||||
if [ -n "$configured_path" ]; then
|
||||
LEARNED_SKILLS_PATH=$(echo "$configured_path" | sed "s|~|$HOME|")
|
||||
case "$LEARNED_SKILLS_PATH" in
|
||||
/*) ;;
|
||||
*) LEARNED_SKILLS_PATH="${ROOT}/${LEARNED_SKILLS_PATH}" ;;
|
||||
esac
|
||||
fi
|
||||
fi
|
||||
|
||||
# Ensure learned skills directory exists
|
||||
mkdir -p "$LEARNED_SKILLS_PATH"
|
||||
|
||||
# Get transcript path from environment (set by Claude Code)
|
||||
transcript_path="${CLAUDE_TRANSCRIPT_PATH:-}"
|
||||
|
||||
if [ -z "$transcript_path" ] || [ ! -f "$transcript_path" ]; then
|
||||
exit 0
|
||||
fi
|
||||
|
||||
# Count messages in session
|
||||
message_count=$(grep -c '"type":"user"' "$transcript_path" 2>/dev/null || echo "0")
|
||||
|
||||
# Skip short sessions
|
||||
if [ "$message_count" -lt "$MIN_SESSION_LENGTH" ]; then
|
||||
echo "[ContinuousLearning] Session too short ($message_count messages), skipping" >&2
|
||||
exit 0
|
||||
fi
|
||||
|
||||
# Signal to Claude that session should be evaluated for extractable patterns
|
||||
echo "[ContinuousLearning] Session has $message_count messages - evaluate for extractable patterns" >&2
|
||||
echo "[ContinuousLearning] Save learned skills to: $LEARNED_SKILLS_PATH" >&2
|
||||
@@ -0,0 +1,444 @@
|
||||
---
|
||||
name: drizzle
|
||||
description: 'LobeHub Drizzle ORM schema and query style. Use for pgTable schemas, indexes, joins, inferred types, db.select/db.query, schema fields, foreign keys, junction tables, or postgres query patterns.'
|
||||
user-invocable: false
|
||||
---
|
||||
|
||||
# Drizzle ORM Schema Style Guide
|
||||
|
||||
> **Adding a Model or Repository?** Ship a sibling test in the same PR — every new
|
||||
> file under `packages/database/src/models/**` or `src/repositories/**` needs a
|
||||
> matching `__tests__/<name>.test.ts`. See the **testing** skill
|
||||
> (`.agents/skills/testing/references/db-model-test.md`) for the `getTestDB()`
|
||||
> integration pattern, user-isolation tests, the BM25 `describe.skipIf(!isServerDB)`
|
||||
> guard, and schema gotchas. CI's coverage patch gate won't reliably catch a brand-new
|
||||
> untested file, so this is on you.
|
||||
|
||||
## Configuration
|
||||
|
||||
- Config: `drizzle.config.ts`
|
||||
- Schemas: `packages/database/src/schemas/`
|
||||
- Migrations: `packages/database/migrations/`
|
||||
- Dialect: `postgresql` with `strict: true`
|
||||
|
||||
## Helper Functions
|
||||
|
||||
Location: `packages/database/src/schemas/_helpers.ts`
|
||||
|
||||
- `timestamptz(name)`: Timestamp with timezone
|
||||
- `createdAt()`, `updatedAt()`, `accessedAt()`: Standard timestamp columns
|
||||
- `timestamps`: Object with all three for easy spread
|
||||
|
||||
## Naming Conventions
|
||||
|
||||
- **Tables**: Plural snake\_case (`users`, `session_groups`)
|
||||
- **Columns**: snake\_case (`user_id`, `created_at`)
|
||||
- **New tables**: Check nearby existing tables before naming a new one. Preserve
|
||||
the established noun family and suffix. For example, if the user-scoped table
|
||||
is `user_xxx_logs`, the workspace-scoped counterpart should be
|
||||
`workspace_xxx_logs`, not `workspace_xxx_records` or another new synonym.
|
||||
|
||||
```typescript
|
||||
// ✅ Good: follows the existing user/workspace table family.
|
||||
export const userSignupLogs = pgTable('user_signup_logs', { ... });
|
||||
export const workspaceSignupLogs = pgTable('workspace_signup_logs', { ... });
|
||||
|
||||
// ❌ Bad: introduces a new suffix for the same concept.
|
||||
export const workspaceSignupRecords = pgTable('workspace_signup_records', { ... });
|
||||
```
|
||||
|
||||
## Column Definitions
|
||||
|
||||
### Primary Keys
|
||||
|
||||
Do not use auto-incrementing primary keys (`serial`, `bigserial`, generated
|
||||
identity columns). They create sequence-state problems during cross-database
|
||||
migrations, restores, and data copy jobs. Prefer text IDs from application
|
||||
generators (`idGenerator`, `createNanoId`) or `uuid` for internal tables.
|
||||
|
||||
Keep `$defaultFn(...)` when a table normally owns ID generation. Callers can
|
||||
still pass an explicit `id`; the default only runs when the insert omits it. Do
|
||||
not remove the default just because one flow needs to supply a request-scoped ID.
|
||||
|
||||
```typescript
|
||||
// ✅ Good: app-generated text ID; explicit inserts can still override it.
|
||||
id: text('id')
|
||||
.primaryKey()
|
||||
.$defaultFn(() => idGenerator('agents'))
|
||||
.notNull(),
|
||||
|
||||
// ❌ Bad: sequence state is fragile across DB migrations and restores.
|
||||
id: serial('id').primaryKey(),
|
||||
```
|
||||
|
||||
ID prefixes make entity types distinguishable. For internal tables, use `uuid`.
|
||||
|
||||
Do not use composite primary keys on new tables. Give every table a single-column
|
||||
surrogate PK and carry business uniqueness in a `uniqueIndex` instead. PK columns
|
||||
cannot be nullable, so when the uniqueness scope later grows by a nullable
|
||||
dimension the composite PK must be torn down and rebuilt — exactly what happened
|
||||
when `ai_providers` / `ai_models` were workspace-scoped (migration 0110 replaced
|
||||
their composite PKs with a surrogate `_id` plus partial unique indexes). A unique
|
||||
index still works as the arbiter for `onConflictDoUpdate` upserts.
|
||||
|
||||
```typescript
|
||||
// ✅ Good: surrogate PK; uniqueness scope can evolve without a PK rebuild.
|
||||
export const workspaceUserSettings = pgTable(
|
||||
'workspace_user_settings',
|
||||
{
|
||||
id: uuid('id').defaultRandom().notNull().primaryKey(),
|
||||
workspaceId: text('workspace_id').references(() => workspaces.id, { onDelete: 'cascade' }).notNull(),
|
||||
userId: text('user_id').references(() => users.id, { onDelete: 'cascade' }).notNull(),
|
||||
...timestamps,
|
||||
},
|
||||
(t) => [uniqueIndex('workspace_user_settings_workspace_id_user_id_unique').on(t.workspaceId, t.userId)],
|
||||
);
|
||||
|
||||
// ❌ Bad: locked to exactly these columns; adding a nullable scope column
|
||||
// (workspaceId, deviceId, …) later forces a full PK rebuild migration.
|
||||
(t) => [primaryKey({ columns: [t.workspaceId, t.userId] })],
|
||||
```
|
||||
|
||||
Existing composite PKs are legacy — leave them alone unless they block a scope
|
||||
change, then migrate them the 0110 way.
|
||||
|
||||
### Foreign Keys
|
||||
|
||||
```typescript
|
||||
userId: text('user_id')
|
||||
.references(() => users.id, { onDelete: 'cascade' })
|
||||
.notNull(),
|
||||
```
|
||||
|
||||
### Timestamps
|
||||
|
||||
```typescript
|
||||
...timestamps, // Spread from _helpers.ts
|
||||
```
|
||||
|
||||
### Optional and Undefined Values
|
||||
|
||||
Do not introduce artificial sentinel strings for missing values, such as
|
||||
`unknown`, unless the domain already has that explicit state and existing code
|
||||
uses it consistently. Prefer nullable columns, optional TypeScript fields, or a
|
||||
separate concrete status enum when the value is genuinely absent.
|
||||
|
||||
```typescript
|
||||
// ✅ Good: absent until the final stage writes a real decision.
|
||||
export type UserSignupLogFinalDecision = 'allow' | 'block' | 'error';
|
||||
|
||||
finalDecision: varchar('final_decision', { length: 32 }).$type<UserSignupLogFinalDecision>(),
|
||||
|
||||
// ❌ Bad: invents a new state that callers now need to handle everywhere.
|
||||
export type UserSignupLogFinalDecision = 'allow' | 'block' | 'error' | 'unknown';
|
||||
|
||||
finalDecision: varchar('final_decision', { length: 32 })
|
||||
.$type<UserSignupLogFinalDecision>()
|
||||
.notNull()
|
||||
.default('unknown');
|
||||
```
|
||||
|
||||
### Database Enums
|
||||
|
||||
Default to **not** using PostgreSQL/Drizzle `pgEnum`. Database enums are
|
||||
expensive to evolve safely: adding members needs migrations, removing or
|
||||
renaming members is awkward, and deployment order becomes more fragile.
|
||||
|
||||
For product/business states, use `text()` or `varchar()` with a TypeScript value
|
||||
type via `$type<...>()`. Keep those TS-only value types in the domain/shared type
|
||||
module, then import them into the schema. For cloud DB schemas, that usually
|
||||
means `cloudDB/types.ts`.
|
||||
|
||||
Do not copy existing DB enums as a pattern. Treat them as legacy or explicitly
|
||||
reviewed exceptions. If a new `pgEnum` seems necessary, stop and justify why the
|
||||
value set is effectively immutable and why the migration cost is acceptable.
|
||||
|
||||
### Field Descriptions
|
||||
|
||||
For columns whose meaning is not obvious from the name alone, add JSDoc on the
|
||||
schema field. Include a concrete example when it clarifies the stored value or
|
||||
the lifecycle moment that writes it. This is especially important for external
|
||||
IDs, lifecycle statuses, denormalized snapshots, JSONB signals, and fields whose
|
||||
name could mean either a request ID or a persisted row ID.
|
||||
|
||||
```typescript
|
||||
// ✅ Good: explain the table's business object first, then only document
|
||||
// non-obvious lifecycle or risk-control fields.
|
||||
/**
|
||||
* User signup logs - one row per signup flow, collecting stage-level
|
||||
* risk-control decisions before and after the auth provider creates a user.
|
||||
*/
|
||||
export const userSignupLogs = pgTable('user_signup_logs', {
|
||||
/** Final signup outcome reason, for example user_created, llm_block, or guard_error */
|
||||
finalReason: text('final_reason'),
|
||||
|
||||
/** Aggregated risk level derived from stage decisions, for example block -> high */
|
||||
riskLevel: varchar('risk_level', { length: 16 }).$type<UserSignupLogRiskLevel>(),
|
||||
|
||||
/** Ordered stage-level decisions and metadata grouped by signup review stage */
|
||||
stageResults: jsonb('stage_results').$type<UserSignupLogStageResults>(),
|
||||
});
|
||||
|
||||
// ❌ Bad: comments restate obvious column names without adding domain meaning.
|
||||
/** User email */
|
||||
email: text('email'),
|
||||
```
|
||||
|
||||
### JSONB Types
|
||||
|
||||
Avoid `Record<string, unknown>` or similarly loose JSONB types for schema
|
||||
columns. Define a concrete interface that describes the expected JSON shape, even
|
||||
when most properties are optional. This keeps callers, migrations, and review
|
||||
queries aligned on the same data contract.
|
||||
|
||||
```typescript
|
||||
interface UserSignupLogMetadata {
|
||||
payloadPath?: string;
|
||||
requestPath?: string;
|
||||
}
|
||||
|
||||
metadata: jsonb('metadata').$type<UserSignupLogMetadata>(),
|
||||
```
|
||||
|
||||
```typescript
|
||||
// ❌ Bad: hides the contract and makes downstream access untyped.
|
||||
metadata: jsonb('metadata').$type<Record<string, unknown>>(),
|
||||
```
|
||||
|
||||
A loosely-typed JSONB column is often a symptom of a deeper problem: the column
|
||||
was reserved speculatively ("for future extension") and nothing actually writes
|
||||
it. Don't add `metadata` / `extra` JSONB columns for hypothetical future needs —
|
||||
a column earns its place only when a concrete writer ships alongside it. When
|
||||
review finds such a column, the fix is to **delete the column**, not to invent
|
||||
an interface for data that doesn't exist; add a properly-typed column once the
|
||||
real requirement arrives.
|
||||
|
||||
### Indexes
|
||||
|
||||
```typescript
|
||||
// Return array (object style deprecated)
|
||||
(t) => [uniqueIndex('client_id_user_id_unique').on(t.clientId, t.userId)],
|
||||
```
|
||||
|
||||
## Type Inference
|
||||
|
||||
```typescript
|
||||
export const insertAgentSchema = createInsertSchema(agents);
|
||||
export type NewAgent = typeof agents.$inferInsert;
|
||||
export type AgentItem = typeof agents.$inferSelect;
|
||||
```
|
||||
|
||||
## Example Pattern
|
||||
|
||||
```typescript
|
||||
export const agents = pgTable(
|
||||
'agents',
|
||||
{
|
||||
id: text('id')
|
||||
.primaryKey()
|
||||
.$defaultFn(() => idGenerator('agents'))
|
||||
.notNull(),
|
||||
slug: varchar('slug', { length: 100 })
|
||||
.$defaultFn(() => randomSlug(4))
|
||||
.unique(),
|
||||
userId: text('user_id')
|
||||
.references(() => users.id, { onDelete: 'cascade' })
|
||||
.notNull(),
|
||||
clientId: text('client_id'),
|
||||
chatConfig: jsonb('chat_config').$type<LobeAgentChatConfig>(),
|
||||
...timestamps,
|
||||
},
|
||||
(t) => [uniqueIndex('client_id_user_id_unique').on(t.clientId, t.userId)],
|
||||
);
|
||||
```
|
||||
|
||||
## Common Patterns
|
||||
|
||||
### Junction Tables (Many-to-Many)
|
||||
|
||||
The surrogate-PK rule above applies to junction tables too — pair uniqueness
|
||||
goes in a `uniqueIndex`, not a composite PK (many existing junction tables
|
||||
still use composite PKs; that is legacy, not the template):
|
||||
|
||||
```typescript
|
||||
export const agentsKnowledgeBases = pgTable(
|
||||
'agents_knowledge_bases',
|
||||
{
|
||||
id: uuid('id').defaultRandom().notNull().primaryKey(),
|
||||
agentId: text('agent_id')
|
||||
.references(() => agents.id, { onDelete: 'cascade' })
|
||||
.notNull(),
|
||||
knowledgeBaseId: text('knowledge_base_id')
|
||||
.references(() => knowledgeBases.id, { onDelete: 'cascade' })
|
||||
.notNull(),
|
||||
userId: text('user_id')
|
||||
.references(() => users.id, { onDelete: 'cascade' })
|
||||
.notNull(),
|
||||
enabled: boolean('enabled').default(true),
|
||||
...timestamps,
|
||||
},
|
||||
(t) => [
|
||||
uniqueIndex('agents_knowledge_bases_agent_id_knowledge_base_id_unique').on(
|
||||
t.agentId,
|
||||
t.knowledgeBaseId,
|
||||
),
|
||||
],
|
||||
);
|
||||
```
|
||||
|
||||
## Query Style
|
||||
|
||||
**Always use `db.select()` builder API. Never use `db.query.*` relational API** (`findMany`, `findFirst`, `with:`).
|
||||
|
||||
The relational API generates complex lateral joins with `json_build_array` that are fragile and hard to debug.
|
||||
|
||||
### Select Single Row
|
||||
|
||||
```typescript
|
||||
// ✅ Good
|
||||
const [result] = await this.db.select().from(agents).where(eq(agents.id, id)).limit(1);
|
||||
return result;
|
||||
|
||||
// ❌ Bad: relational API
|
||||
return this.db.query.agents.findFirst({
|
||||
where: eq(agents.id, id),
|
||||
});
|
||||
```
|
||||
|
||||
### Select with JOIN
|
||||
|
||||
```typescript
|
||||
// ✅ Good: explicit select + leftJoin
|
||||
const rows = await this.db
|
||||
.select({
|
||||
runId: agentEvalRunTopics.runId,
|
||||
score: agentEvalRunTopics.score,
|
||||
testCase: agentEvalTestCases,
|
||||
topic: topics,
|
||||
})
|
||||
.from(agentEvalRunTopics)
|
||||
.leftJoin(agentEvalTestCases, eq(agentEvalRunTopics.testCaseId, agentEvalTestCases.id))
|
||||
.leftJoin(topics, eq(agentEvalRunTopics.topicId, topics.id))
|
||||
.where(eq(agentEvalRunTopics.runId, runId))
|
||||
.orderBy(asc(agentEvalRunTopics.createdAt));
|
||||
|
||||
// ❌ Bad: relational API with `with:`
|
||||
return this.db.query.agentEvalRunTopics.findMany({
|
||||
where: eq(agentEvalRunTopics.runId, runId),
|
||||
with: { testCase: true, topic: true },
|
||||
});
|
||||
```
|
||||
|
||||
### Select with Aggregation
|
||||
|
||||
```typescript
|
||||
// ✅ Good: select + leftJoin + groupBy
|
||||
const rows = await this.db
|
||||
.select({
|
||||
id: agentEvalDatasets.id,
|
||||
name: agentEvalDatasets.name,
|
||||
testCaseCount: count(agentEvalTestCases.id).as('testCaseCount'),
|
||||
})
|
||||
.from(agentEvalDatasets)
|
||||
.leftJoin(agentEvalTestCases, eq(agentEvalDatasets.id, agentEvalTestCases.datasetId))
|
||||
.groupBy(agentEvalDatasets.id);
|
||||
```
|
||||
|
||||
### Raw SQL and Advanced Queries
|
||||
|
||||
Prefer Drizzle builders whenever the query reads clearly with `select`,
|
||||
`insert().select()`, `update().from()`, joins, CTEs, and `groupBy` — this keeps
|
||||
table/column references tied to schema, so changes surface as TypeScript errors.
|
||||
Within a builder, expression-level `sql<T>` is fine for features lacking a helper
|
||||
(JSON path, casts, aggregates, `CASE`, `NOW()`). Row locks are clauses, not
|
||||
expressions — use `.for('update')`, never raw `FOR UPDATE`.
|
||||
|
||||
Use `COALESCE` only when null-handling is part of required DB semantics (nullable
|
||||
JSONB append/merge, "keep first non-null"). Don't scatter
|
||||
`COALESCE(excluded.col, current.col)` across ordinary upsert scalars just to avoid
|
||||
an update object — build `set` from defined values only, and hide any remaining
|
||||
SQL behind named helpers (`appendJsonbArray`, `mergeJsonbObject`, `keepFirstValue`)
|
||||
so the method reads as business intent, not SQL plumbing.
|
||||
|
||||
```typescript
|
||||
// ✅ Scalars included only when present; SQL hidden behind a named helper.
|
||||
const updateValues = compactUndefined({
|
||||
email: record.email ?? undefined,
|
||||
ip: record.ip ?? undefined,
|
||||
});
|
||||
await db.insert(userSignupLogs).values(values).onConflictDoUpdate({
|
||||
set: { ...updateValues, stageResults: appendStageResult(stage, result), updatedAt: now },
|
||||
target: userSignupLogs.id,
|
||||
});
|
||||
|
||||
// ❌ Every scalar becomes SQL plumbing.
|
||||
set: {
|
||||
email: sql`COALESCE(excluded.email, ${userSignupLogs.email})`,
|
||||
ip: sql`COALESCE(excluded.ip, ${userSignupLogs.ip})`,
|
||||
}
|
||||
```
|
||||
|
||||
When refactoring raw SQL:
|
||||
|
||||
- Preserve query shape on latency-sensitive paths. If raw SQL is one roundtrip,
|
||||
don't split it into multiple depth-based queries just to drop `execute`.
|
||||
- Use `$with(...)` + `insert().select()` / `update().from()` for multi-step
|
||||
single-roundtrip writes Drizzle can express.
|
||||
- Don't rely on `execute<MyRow>(sql...)` for safety — it types rows but doesn't keep
|
||||
selected columns in sync with schema changes.
|
||||
- If only a PostgreSQL feature Drizzle can't express works, keep the raw SQL and
|
||||
tighten it: schema refs in interpolations, explicit user scope, a narrow row
|
||||
interface, and regression tests.
|
||||
|
||||
Recursive CTEs are the canonical "keep raw" case — there's no clean `WITH RECURSIVE`
|
||||
builder, and a rewrite would add depth-based roundtrips:
|
||||
|
||||
```typescript
|
||||
interface TaskTreeRow {
|
||||
id: string;
|
||||
parent_task_id: string | null;
|
||||
}
|
||||
|
||||
// execute<T> acceptable: no clean WITH RECURSIVE builder. Keep schema refs in the
|
||||
// interpolations and scope every leg to the user.
|
||||
const { rows } = await db.execute<TaskTreeRow>(sql`
|
||||
WITH RECURSIVE task_tree AS (
|
||||
SELECT ${tasks.id}, ${tasks.parentTaskId}
|
||||
FROM ${tasks}
|
||||
WHERE ${tasks.id} = ${rootTaskId} AND ${tasks.createdByUserId} = ${userId}
|
||||
UNION ALL
|
||||
SELECT ${tasks.id}, ${tasks.parentTaskId}
|
||||
FROM ${tasks}
|
||||
JOIN task_tree ON ${tasks.parentTaskId} = task_tree.id
|
||||
WHERE ${tasks.createdByUserId} = ${userId}
|
||||
)
|
||||
SELECT * FROM task_tree
|
||||
`);
|
||||
```
|
||||
|
||||
### One-to-Many (Separate Queries)
|
||||
|
||||
When you need a parent record with its children, use two queries instead of relational `with:`:
|
||||
|
||||
```typescript
|
||||
// ✅ Good: two simple queries
|
||||
const [dataset] = await this.db
|
||||
.select()
|
||||
.from(agentEvalDatasets)
|
||||
.where(eq(agentEvalDatasets.id, id))
|
||||
.limit(1);
|
||||
|
||||
if (!dataset) return undefined;
|
||||
|
||||
const testCases = await this.db
|
||||
.select()
|
||||
.from(agentEvalTestCases)
|
||||
.where(eq(agentEvalTestCases.datasetId, id))
|
||||
.orderBy(asc(agentEvalTestCases.sortOrder));
|
||||
|
||||
return { ...dataset, testCases };
|
||||
```
|
||||
|
||||
## Database Migrations
|
||||
|
||||
See the `db-migrations` skill for the detailed migration guide.
|
||||
@@ -0,0 +1,221 @@
|
||||
# Eval Harness Skill
|
||||
|
||||
A formal evaluation framework for Claude Code sessions, implementing eval-driven development (EDD) principles.
|
||||
|
||||
## Philosophy
|
||||
|
||||
Eval-Driven Development treats evals as the "unit tests of AI development":
|
||||
- Define expected behavior BEFORE implementation
|
||||
- Run evals continuously during development
|
||||
- Track regressions with each change
|
||||
- Use pass@k metrics for reliability measurement
|
||||
|
||||
## Eval Types
|
||||
|
||||
### Capability Evals
|
||||
Test if Claude can do something it couldn't before:
|
||||
```markdown
|
||||
[CAPABILITY EVAL: feature-name]
|
||||
Task: Description of what Claude should accomplish
|
||||
Success Criteria:
|
||||
- [ ] Criterion 1
|
||||
- [ ] Criterion 2
|
||||
- [ ] Criterion 3
|
||||
Expected Output: Description of expected result
|
||||
```
|
||||
|
||||
### Regression Evals
|
||||
Ensure changes don't break existing functionality:
|
||||
```markdown
|
||||
[REGRESSION EVAL: feature-name]
|
||||
Baseline: SHA or checkpoint name
|
||||
Tests:
|
||||
- existing-test-1: PASS/FAIL
|
||||
- existing-test-2: PASS/FAIL
|
||||
- existing-test-3: PASS/FAIL
|
||||
Result: X/Y passed (previously Y/Y)
|
||||
```
|
||||
|
||||
## Grader Types
|
||||
|
||||
### 1. Code-Based Grader
|
||||
Deterministic checks using code:
|
||||
```bash
|
||||
# Check if file contains expected pattern
|
||||
grep -q "export function handleAuth" src/auth.ts && echo "PASS" || echo "FAIL"
|
||||
|
||||
# Check if tests pass
|
||||
npm test -- --testPathPattern="auth" && echo "PASS" || echo "FAIL"
|
||||
|
||||
# Check if build succeeds
|
||||
npm run build && echo "PASS" || echo "FAIL"
|
||||
```
|
||||
|
||||
### 2. Model-Based Grader
|
||||
Use Claude to evaluate open-ended outputs:
|
||||
```markdown
|
||||
[MODEL GRADER PROMPT]
|
||||
Evaluate the following code change:
|
||||
1. Does it solve the stated problem?
|
||||
2. Is it well-structured?
|
||||
3. Are edge cases handled?
|
||||
4. Is error handling appropriate?
|
||||
|
||||
Score: 1-5 (1=poor, 5=excellent)
|
||||
Reasoning: [explanation]
|
||||
```
|
||||
|
||||
### 3. Human Grader
|
||||
Flag for manual review:
|
||||
```markdown
|
||||
[HUMAN REVIEW REQUIRED]
|
||||
Change: Description of what changed
|
||||
Reason: Why human review is needed
|
||||
Risk Level: LOW/MEDIUM/HIGH
|
||||
```
|
||||
|
||||
## Metrics
|
||||
|
||||
### pass@k
|
||||
"At least one success in k attempts"
|
||||
- pass@1: First attempt success rate
|
||||
- pass@3: Success within 3 attempts
|
||||
- Typical target: pass@3 > 90%
|
||||
|
||||
### pass^k
|
||||
"All k trials succeed"
|
||||
- Higher bar for reliability
|
||||
- pass^3: 3 consecutive successes
|
||||
- Use for critical paths
|
||||
|
||||
## Eval Workflow
|
||||
|
||||
### 1. Define (Before Coding)
|
||||
```markdown
|
||||
## EVAL DEFINITION: feature-xyz
|
||||
|
||||
### Capability Evals
|
||||
1. Can create new user account
|
||||
2. Can validate email format
|
||||
3. Can hash password securely
|
||||
|
||||
### Regression Evals
|
||||
1. Existing login still works
|
||||
2. Session management unchanged
|
||||
3. Logout flow intact
|
||||
|
||||
### Success Metrics
|
||||
- pass@3 > 90% for capability evals
|
||||
- pass^3 = 100% for regression evals
|
||||
```
|
||||
|
||||
### 2. Implement
|
||||
Write code to pass the defined evals.
|
||||
|
||||
### 3. Evaluate
|
||||
```bash
|
||||
# Run capability evals
|
||||
[Run each capability eval, record PASS/FAIL]
|
||||
|
||||
# Run regression evals
|
||||
npm test -- --testPathPattern="existing"
|
||||
|
||||
# Generate report
|
||||
```
|
||||
|
||||
### 4. Report
|
||||
```markdown
|
||||
EVAL REPORT: feature-xyz
|
||||
========================
|
||||
|
||||
Capability Evals:
|
||||
create-user: PASS (pass@1)
|
||||
validate-email: PASS (pass@2)
|
||||
hash-password: PASS (pass@1)
|
||||
Overall: 3/3 passed
|
||||
|
||||
Regression Evals:
|
||||
login-flow: PASS
|
||||
session-mgmt: PASS
|
||||
logout-flow: PASS
|
||||
Overall: 3/3 passed
|
||||
|
||||
Metrics:
|
||||
pass@1: 67% (2/3)
|
||||
pass@3: 100% (3/3)
|
||||
|
||||
Status: READY FOR REVIEW
|
||||
```
|
||||
|
||||
## Integration Patterns
|
||||
|
||||
### Pre-Implementation
|
||||
```
|
||||
/eval define feature-name
|
||||
```
|
||||
Creates eval definition file at `.cursor/evals/feature-name.md`
|
||||
|
||||
### During Implementation
|
||||
```
|
||||
/eval check feature-name
|
||||
```
|
||||
Runs current evals and reports status
|
||||
|
||||
### Post-Implementation
|
||||
```
|
||||
/eval report feature-name
|
||||
```
|
||||
Generates full eval report
|
||||
|
||||
## Eval Storage
|
||||
|
||||
Store evals in project:
|
||||
```
|
||||
.cursor/
|
||||
evals/
|
||||
feature-xyz.md # Eval definition
|
||||
feature-xyz.log # Eval run history
|
||||
baseline.json # Regression baselines
|
||||
```
|
||||
|
||||
## Best Practices
|
||||
|
||||
1. **Define evals BEFORE coding** - Forces clear thinking about success criteria
|
||||
2. **Run evals frequently** - Catch regressions early
|
||||
3. **Track pass@k over time** - Monitor reliability trends
|
||||
4. **Use code graders when possible** - Deterministic > probabilistic
|
||||
5. **Human review for security** - Never fully automate security checks
|
||||
6. **Keep evals fast** - Slow evals don't get run
|
||||
7. **Version evals with code** - Evals are first-class artifacts
|
||||
|
||||
## Example: Adding Authentication
|
||||
|
||||
```markdown
|
||||
## EVAL: add-authentication
|
||||
|
||||
### Phase 1: Define (10 min)
|
||||
Capability Evals:
|
||||
- [ ] User can register with email/password
|
||||
- [ ] User can login with valid credentials
|
||||
- [ ] Invalid credentials rejected with proper error
|
||||
- [ ] Sessions persist across page reloads
|
||||
- [ ] Logout clears session
|
||||
|
||||
Regression Evals:
|
||||
- [ ] Public routes still accessible
|
||||
- [ ] API responses unchanged
|
||||
- [ ] Database schema compatible
|
||||
|
||||
### Phase 2: Implement (varies)
|
||||
[Write code]
|
||||
|
||||
### Phase 3: Evaluate
|
||||
Run: /eval check add-authentication
|
||||
|
||||
### Phase 4: Report
|
||||
EVAL REPORT: add-authentication
|
||||
==============================
|
||||
Capability: 5/5 passed (pass@3: 100%)
|
||||
Regression: 3/3 passed (pass^3: 100%)
|
||||
Status: SHIP IT
|
||||
```
|
||||
@@ -0,0 +1,131 @@
|
||||
---
|
||||
name: nestjs-best-practices
|
||||
description: NestJS best practices and architecture patterns for building production-ready applications. This skill should be used when writing, reviewing, or refactoring NestJS code to ensure proper patterns for modules, dependency injection, security, and performance.
|
||||
license: MIT
|
||||
metadata:
|
||||
author: Kadajett
|
||||
version: "1.2.0"
|
||||
---
|
||||
|
||||
# NestJS Best Practices
|
||||
|
||||
When a rule mentions TypeORM, apply the same idea with **Drizzle ORM** (`drizzle/schema.ts` and `drizzle-kit` migrations). This project does not use TypeORM.
|
||||
|
||||
## When to Apply
|
||||
|
||||
Reference these guidelines when:
|
||||
|
||||
- Writing new NestJS modules, controllers, or services
|
||||
- Implementing authentication and authorization
|
||||
- Reviewing code for architecture and security issues
|
||||
- Refactoring existing NestJS codebases
|
||||
- Optimizing performance or database queries
|
||||
- Building microservices architectures
|
||||
|
||||
## Rule Categories by Priority
|
||||
|
||||
| Priority | Category | Impact | Prefix |
|
||||
|----------|----------|--------|--------|
|
||||
| 1 | Architecture | CRITICAL | `arch-` |
|
||||
| 2 | Dependency Injection | CRITICAL | `di-` |
|
||||
| 3 | Error Handling | HIGH | `error-` |
|
||||
| 4 | Security | HIGH | `security-` |
|
||||
| 5 | Performance | HIGH | `perf-` |
|
||||
| 6 | Testing | MEDIUM-HIGH | `test-` |
|
||||
| 7 | Database & ORM | MEDIUM-HIGH | `db-` |
|
||||
| 8 | API Design | MEDIUM | `api-` |
|
||||
| 9 | Microservices | MEDIUM | `micro-` |
|
||||
| 10 | DevOps & Deployment | LOW-MEDIUM | `devops-` |
|
||||
|
||||
## Quick Reference
|
||||
|
||||
### 1. Architecture (CRITICAL)
|
||||
|
||||
- `arch-avoid-circular-deps` - Avoid circular module dependencies
|
||||
- `arch-feature-modules` - Organize by feature, not technical layer
|
||||
- `arch-module-sharing` - Proper module exports/imports, avoid duplicate providers
|
||||
- `arch-single-responsibility` - Focused services over "god services"
|
||||
- `arch-use-repository-pattern` - Abstract database logic for testability
|
||||
- `arch-use-events` - Event-driven architecture for decoupling
|
||||
|
||||
### 2. Dependency Injection (CRITICAL)
|
||||
|
||||
- `di-avoid-service-locator` - Avoid service locator anti-pattern
|
||||
- `di-interface-segregation` - Interface Segregation Principle (ISP)
|
||||
- `di-liskov-substitution` - Liskov Substitution Principle (LSP)
|
||||
- `di-prefer-constructor-injection` - Constructor over property injection
|
||||
- `di-scope-awareness` - Understand singleton/request/transient scopes
|
||||
- `di-use-interfaces-tokens` - Use injection tokens for interfaces
|
||||
|
||||
### 3. Error Handling (HIGH)
|
||||
|
||||
- `error-use-exception-filters` - Centralized exception handling
|
||||
- `error-throw-http-exceptions` - Use NestJS HTTP exceptions
|
||||
- `error-handle-async-errors` - Handle async errors properly
|
||||
|
||||
### 4. Security (HIGH)
|
||||
|
||||
- `security-auth-jwt` - Secure JWT authentication
|
||||
- `security-validate-all-input` - Validate with class-validator
|
||||
- `security-use-guards` - Authentication and authorization guards
|
||||
- `security-sanitize-output` - Prevent XSS attacks
|
||||
- `security-rate-limiting` - Implement rate limiting
|
||||
|
||||
### 5. Performance (HIGH)
|
||||
|
||||
- `perf-async-hooks` - Proper async lifecycle hooks
|
||||
- `perf-use-caching` - Implement caching strategies
|
||||
- `perf-optimize-database` - Optimize database queries
|
||||
- `perf-lazy-loading` - Lazy load modules for faster startup
|
||||
|
||||
### 6. Testing (MEDIUM-HIGH)
|
||||
|
||||
- `test-use-testing-module` - Use NestJS testing utilities
|
||||
- `test-e2e-supertest` - E2E testing with Supertest
|
||||
- `test-mock-external-services` - Mock external dependencies
|
||||
|
||||
### 7. Database & ORM (MEDIUM-HIGH)
|
||||
|
||||
- `db-use-transactions` - Transaction management
|
||||
- `db-avoid-n-plus-one` - Avoid N+1 query problems
|
||||
- `db-use-migrations` - Use migrations for schema changes
|
||||
|
||||
### 8. API Design (MEDIUM)
|
||||
|
||||
- `api-use-dto-serialization` - DTO and response serialization
|
||||
- `api-use-interceptors` - Cross-cutting concerns
|
||||
- `api-versioning` - API versioning strategies
|
||||
- `api-use-pipes` - Input transformation with pipes
|
||||
|
||||
### 9. Microservices (MEDIUM)
|
||||
|
||||
- `micro-use-patterns` - Message and event patterns
|
||||
- `micro-use-health-checks` - Health checks for orchestration
|
||||
- `micro-use-queues` - Background job processing
|
||||
|
||||
### 10. DevOps & Deployment (LOW-MEDIUM)
|
||||
|
||||
- `devops-use-config-module` - Environment configuration
|
||||
- `devops-use-logging` - Structured logging
|
||||
- `devops-graceful-shutdown` - Zero-downtime deployments
|
||||
|
||||
## How to Use
|
||||
|
||||
Read individual rule files for detailed explanations and code examples:
|
||||
|
||||
```
|
||||
rules/arch-avoid-circular-deps.md
|
||||
rules/security-validate-all-input.md
|
||||
rules/_sections.md
|
||||
```
|
||||
|
||||
Each rule file contains:
|
||||
- Brief explanation of why it matters
|
||||
- Incorrect code example with explanation
|
||||
- Correct code example with explanation
|
||||
- Additional context and references
|
||||
|
||||
## Full Compiled Document
|
||||
|
||||
For the complete guide with all rules expanded in a single document, see
|
||||
[AGENTS.md in the repository](https://github.com/Kadajett/agent-nestjs-skills/blob/main/AGENTS.md).
|
||||
@@ -0,0 +1,56 @@
|
||||
# Sections
|
||||
|
||||
This file defines all sections, their ordering, impact levels, and descriptions.
|
||||
The section ID (in parentheses) is the filename prefix used to group rules.
|
||||
|
||||
---
|
||||
|
||||
## 1. Architecture (arch)
|
||||
|
||||
**Impact:** CRITICAL
|
||||
**Description:** Proper module organization and dependency management are the foundation of maintainable NestJS applications. Circular dependencies and god services are the #1 architecture killer.
|
||||
|
||||
## 2. Dependency Injection (di)
|
||||
|
||||
**Impact:** CRITICAL
|
||||
**Description:** NestJS's IoC container is powerful but can be misused. Understanding scopes, injection tokens, and proper patterns is essential for testable code.
|
||||
|
||||
## 3. Error Handling (error)
|
||||
|
||||
**Impact:** HIGH
|
||||
**Description:** Consistent error handling improves debugging, user experience, and API reliability. Centralized exception filters ensure uniform error responses.
|
||||
|
||||
## 4. Security (security)
|
||||
|
||||
**Impact:** HIGH
|
||||
**Description:** Security vulnerabilities can be catastrophic. Input validation, authentication, authorization, and data protection are non-negotiable.
|
||||
|
||||
## 5. Performance (perf)
|
||||
|
||||
**Impact:** HIGH
|
||||
**Description:** Optimizing request handling, caching, and database queries directly impacts application responsiveness and scalability.
|
||||
|
||||
## 6. Testing (test)
|
||||
|
||||
**Impact:** MEDIUM-HIGH
|
||||
**Description:** Well-tested applications are more reliable. NestJS testing utilities enable comprehensive unit and e2e coverage.
|
||||
|
||||
## 7. Database & ORM (db)
|
||||
|
||||
**Impact:** MEDIUM-HIGH
|
||||
**Description:** Proper database access patterns, transactions, and query optimization are crucial for data-intensive applications.
|
||||
|
||||
## 8. API Design (api)
|
||||
|
||||
**Impact:** MEDIUM
|
||||
**Description:** RESTful conventions, versioning, DTOs, and consistent response formats improve API usability and maintainability.
|
||||
|
||||
## 9. Microservices (micro)
|
||||
|
||||
**Impact:** MEDIUM
|
||||
**Description:** Building distributed systems requires understanding message patterns, health checks, and inter-service communication.
|
||||
|
||||
## 10. DevOps & Deployment (devops)
|
||||
|
||||
**Impact:** LOW-MEDIUM
|
||||
**Description:** Configuration management, structured logging, and graceful shutdown ensure production readiness and zero-downtime deployments.
|
||||
@@ -0,0 +1,28 @@
|
||||
---
|
||||
title: Rule Title Here
|
||||
impact: MEDIUM
|
||||
impactDescription: Optional description of impact (e.g., "20-50% improvement")
|
||||
tags: tag1, tag2
|
||||
---
|
||||
|
||||
## Rule Title Here
|
||||
|
||||
**Impact: MEDIUM (optional impact description)**
|
||||
|
||||
Brief explanation of the rule and why it matters. This should be clear and concise, explaining the performance implications.
|
||||
|
||||
**Incorrect (description of what's wrong):**
|
||||
|
||||
```typescript
|
||||
// Bad code example here
|
||||
const bad = example()
|
||||
```
|
||||
|
||||
**Correct (description of what's right):**
|
||||
|
||||
```typescript
|
||||
// Good code example here
|
||||
const good = example()
|
||||
```
|
||||
|
||||
Reference: [Link to documentation or resource](https://example.com)
|
||||
@@ -0,0 +1,182 @@
|
||||
---
|
||||
title: Use DTOs and Serialization for API Responses
|
||||
impact: MEDIUM
|
||||
impactDescription: Response DTOs prevent accidental data exposure and ensure consistency
|
||||
tags: api, dto, serialization, class-transformer
|
||||
---
|
||||
|
||||
## Use DTOs and Serialization for API Responses
|
||||
|
||||
Never return entity objects directly from controllers. Use response DTOs with class-transformer's `@Exclude()` and `@Expose()` decorators to control exactly what data is sent to clients. This prevents accidental exposure of sensitive fields and provides a stable API contract.
|
||||
|
||||
**Incorrect (returning entities directly or manual spreading):**
|
||||
|
||||
```typescript
|
||||
// Return entities directly
|
||||
@Controller('users')
|
||||
export class UsersController {
|
||||
@Get(':id')
|
||||
async findOne(@Param('id') id: string): Promise<User> {
|
||||
return this.usersService.findById(id);
|
||||
// Returns: { id, email, passwordHash, ssn, internalNotes, ... }
|
||||
// Exposes sensitive data!
|
||||
}
|
||||
}
|
||||
|
||||
// Manual object spreading (error-prone)
|
||||
@Get(':id')
|
||||
async findOne(@Param('id') id: string) {
|
||||
const user = await this.usersService.findById(id);
|
||||
return {
|
||||
id: user.id,
|
||||
email: user.email,
|
||||
name: user.name,
|
||||
// Easy to forget to exclude sensitive fields
|
||||
// Hard to maintain across endpoints
|
||||
};
|
||||
}
|
||||
```
|
||||
|
||||
**Correct (use class-transformer with @Exclude and response DTOs):**
|
||||
|
||||
```typescript
|
||||
// Enable class-transformer globally
|
||||
async function bootstrap() {
|
||||
const app = await NestFactory.create(AppModule);
|
||||
app.useGlobalInterceptors(new ClassSerializerInterceptor(app.get(Reflector)));
|
||||
await app.listen(3000);
|
||||
}
|
||||
|
||||
// Entity with serialization control
|
||||
@Entity()
|
||||
export class User {
|
||||
@PrimaryGeneratedColumn('uuid')
|
||||
id: string;
|
||||
|
||||
@Column()
|
||||
email: string;
|
||||
|
||||
@Column()
|
||||
name: string;
|
||||
|
||||
@Column()
|
||||
@Exclude() // Never include in responses
|
||||
passwordHash: string;
|
||||
|
||||
@Column({ nullable: true })
|
||||
@Exclude()
|
||||
ssn: string;
|
||||
|
||||
@Column({ default: false })
|
||||
@Exclude({ toPlainOnly: true }) // Exclude from response, allow in requests
|
||||
isAdmin: boolean;
|
||||
|
||||
@CreateDateColumn()
|
||||
createdAt: Date;
|
||||
|
||||
@Column()
|
||||
@Exclude()
|
||||
internalNotes: string;
|
||||
}
|
||||
|
||||
// Now returning entity is safe
|
||||
@Controller('users')
|
||||
export class UsersController {
|
||||
@Get(':id')
|
||||
async findOne(@Param('id') id: string): Promise<User> {
|
||||
return this.usersService.findById(id);
|
||||
// Returns: { id, email, name, createdAt }
|
||||
// Sensitive fields excluded automatically
|
||||
}
|
||||
}
|
||||
|
||||
// For different response shapes, use explicit DTOs
|
||||
export class UserResponseDto {
|
||||
@Expose()
|
||||
id: string;
|
||||
|
||||
@Expose()
|
||||
email: string;
|
||||
|
||||
@Expose()
|
||||
name: string;
|
||||
|
||||
@Expose()
|
||||
@Transform(({ obj }) => obj.posts?.length || 0)
|
||||
postCount: number;
|
||||
|
||||
constructor(partial: Partial<User>) {
|
||||
Object.assign(this, partial);
|
||||
}
|
||||
}
|
||||
|
||||
export class UserDetailResponseDto extends UserResponseDto {
|
||||
@Expose()
|
||||
createdAt: Date;
|
||||
|
||||
@Expose()
|
||||
@Type(() => PostResponseDto)
|
||||
posts: PostResponseDto[];
|
||||
}
|
||||
|
||||
// Controller with explicit DTOs
|
||||
@Controller('users')
|
||||
export class UsersController {
|
||||
@Get()
|
||||
@SerializeOptions({ type: UserResponseDto })
|
||||
async findAll(): Promise<UserResponseDto[]> {
|
||||
const users = await this.usersService.findAll();
|
||||
return users.map(u => plainToInstance(UserResponseDto, u));
|
||||
}
|
||||
|
||||
@Get(':id')
|
||||
async findOne(@Param('id') id: string): Promise<UserDetailResponseDto> {
|
||||
const user = await this.usersService.findByIdWithPosts(id);
|
||||
return plainToInstance(UserDetailResponseDto, user, {
|
||||
excludeExtraneousValues: true,
|
||||
});
|
||||
}
|
||||
}
|
||||
|
||||
// Groups for conditional serialization
|
||||
export class UserDto {
|
||||
@Expose()
|
||||
id: string;
|
||||
|
||||
@Expose()
|
||||
name: string;
|
||||
|
||||
@Expose({ groups: ['admin'] })
|
||||
email: string;
|
||||
|
||||
@Expose({ groups: ['admin'] })
|
||||
createdAt: Date;
|
||||
|
||||
@Expose({ groups: ['admin', 'owner'] })
|
||||
settings: UserSettings;
|
||||
}
|
||||
|
||||
@Controller('users')
|
||||
export class UsersController {
|
||||
@Get()
|
||||
@SerializeOptions({ groups: ['public'] })
|
||||
async findAllPublic(): Promise<UserDto[]> {
|
||||
// Returns: { id, name }
|
||||
}
|
||||
|
||||
@Get('admin')
|
||||
@UseGuards(AdminGuard)
|
||||
@SerializeOptions({ groups: ['admin'] })
|
||||
async findAllAdmin(): Promise<UserDto[]> {
|
||||
// Returns: { id, name, email, createdAt }
|
||||
}
|
||||
|
||||
@Get('me')
|
||||
@SerializeOptions({ groups: ['owner'] })
|
||||
async getProfile(@CurrentUser() user: User): Promise<UserDto> {
|
||||
// Returns: { id, name, settings }
|
||||
}
|
||||
}
|
||||
```
|
||||
|
||||
Reference: [NestJS Serialization](https://docs.nestjs.com/techniques/serialization)
|
||||
@@ -0,0 +1,202 @@
|
||||
---
|
||||
title: Use Interceptors for Cross-Cutting Concerns
|
||||
impact: MEDIUM-HIGH
|
||||
impactDescription: Interceptors provide clean separation for cross-cutting logic
|
||||
tags: api, interceptors, logging, caching
|
||||
---
|
||||
|
||||
## Use Interceptors for Cross-Cutting Concerns
|
||||
|
||||
Interceptors can transform responses, add logging, handle caching, and measure performance without polluting your business logic. They wrap the route handler execution, giving you access to both the request and response streams.
|
||||
|
||||
**Incorrect (logging and transformation in every method):**
|
||||
|
||||
```typescript
|
||||
// Logging in every controller method
|
||||
@Controller('users')
|
||||
export class UsersController {
|
||||
@Get()
|
||||
async findAll(): Promise<User[]> {
|
||||
const start = Date.now();
|
||||
this.logger.log('findAll called');
|
||||
|
||||
const users = await this.usersService.findAll();
|
||||
|
||||
this.logger.log(`findAll completed in ${Date.now() - start}ms`);
|
||||
return users;
|
||||
}
|
||||
|
||||
@Get(':id')
|
||||
async findOne(@Param('id') id: string): Promise<User> {
|
||||
const start = Date.now();
|
||||
this.logger.log(`findOne called with id: ${id}`);
|
||||
|
||||
const user = await this.usersService.findOne(id);
|
||||
|
||||
this.logger.log(`findOne completed in ${Date.now() - start}ms`);
|
||||
return user;
|
||||
}
|
||||
// Repeated in every method!
|
||||
}
|
||||
|
||||
// Manual response wrapping
|
||||
@Get()
|
||||
async findAll(): Promise<{ data: User[]; meta: Meta }> {
|
||||
const users = await this.usersService.findAll();
|
||||
return {
|
||||
data: users,
|
||||
meta: { timestamp: new Date(), count: users.length },
|
||||
};
|
||||
}
|
||||
```
|
||||
|
||||
**Correct (use interceptors for cross-cutting concerns):**
|
||||
|
||||
```typescript
|
||||
// Logging interceptor
|
||||
@Injectable()
|
||||
export class LoggingInterceptor implements NestInterceptor {
|
||||
private readonly logger = new Logger('HTTP');
|
||||
|
||||
intercept(context: ExecutionContext, next: CallHandler): Observable<any> {
|
||||
const request = context.switchToHttp().getRequest();
|
||||
const { method, url, body } = request;
|
||||
const now = Date.now();
|
||||
|
||||
return next.handle().pipe(
|
||||
tap({
|
||||
next: (data) => {
|
||||
const response = context.switchToHttp().getResponse();
|
||||
this.logger.log(
|
||||
`${method} ${url} ${response.statusCode} - ${Date.now() - now}ms`,
|
||||
);
|
||||
},
|
||||
error: (error) => {
|
||||
this.logger.error(
|
||||
`${method} ${url} ${error.status || 500} - ${Date.now() - now}ms`,
|
||||
error.stack,
|
||||
);
|
||||
},
|
||||
}),
|
||||
);
|
||||
}
|
||||
}
|
||||
|
||||
// Response transformation interceptor
|
||||
@Injectable()
|
||||
export class TransformInterceptor<T> implements NestInterceptor<T, Response<T>> {
|
||||
intercept(context: ExecutionContext, next: CallHandler): Observable<Response<T>> {
|
||||
return next.handle().pipe(
|
||||
map((data) => ({
|
||||
data,
|
||||
meta: {
|
||||
timestamp: new Date().toISOString(),
|
||||
path: context.switchToHttp().getRequest().url,
|
||||
},
|
||||
})),
|
||||
);
|
||||
}
|
||||
}
|
||||
|
||||
// Timeout interceptor
|
||||
@Injectable()
|
||||
export class TimeoutInterceptor implements NestInterceptor {
|
||||
intercept(context: ExecutionContext, next: CallHandler): Observable<any> {
|
||||
return next.handle().pipe(
|
||||
timeout(5000),
|
||||
catchError((err) => {
|
||||
if (err instanceof TimeoutError) {
|
||||
throw new RequestTimeoutException('Request timed out');
|
||||
}
|
||||
throw err;
|
||||
}),
|
||||
);
|
||||
}
|
||||
}
|
||||
|
||||
// Apply globally or per-controller
|
||||
@Module({
|
||||
providers: [
|
||||
{ provide: APP_INTERCEPTOR, useClass: LoggingInterceptor },
|
||||
{ provide: APP_INTERCEPTOR, useClass: TransformInterceptor },
|
||||
],
|
||||
})
|
||||
export class AppModule {}
|
||||
|
||||
// Or per-controller
|
||||
@Controller('users')
|
||||
@UseInterceptors(LoggingInterceptor)
|
||||
export class UsersController {
|
||||
@Get()
|
||||
async findAll(): Promise<User[]> {
|
||||
// Clean business logic only
|
||||
return this.usersService.findAll();
|
||||
}
|
||||
}
|
||||
|
||||
// Custom cache interceptor with TTL
|
||||
@Injectable()
|
||||
export class HttpCacheInterceptor implements NestInterceptor {
|
||||
constructor(
|
||||
private cacheManager: Cache,
|
||||
private reflector: Reflector,
|
||||
) {}
|
||||
|
||||
async intercept(context: ExecutionContext, next: CallHandler): Promise<Observable<any>> {
|
||||
const request = context.switchToHttp().getRequest();
|
||||
|
||||
// Only cache GET requests
|
||||
if (request.method !== 'GET') {
|
||||
return next.handle();
|
||||
}
|
||||
|
||||
const cacheKey = this.generateKey(request);
|
||||
const ttl = this.reflector.get<number>('cacheTTL', context.getHandler()) || 300;
|
||||
|
||||
const cached = await this.cacheManager.get(cacheKey);
|
||||
if (cached) {
|
||||
return of(cached);
|
||||
}
|
||||
|
||||
return next.handle().pipe(
|
||||
tap((response) => {
|
||||
this.cacheManager.set(cacheKey, response, ttl);
|
||||
}),
|
||||
);
|
||||
}
|
||||
|
||||
private generateKey(request: Request): string {
|
||||
return `cache:${request.url}:${JSON.stringify(request.query)}`;
|
||||
}
|
||||
}
|
||||
|
||||
// Usage with custom TTL
|
||||
@Get()
|
||||
@SetMetadata('cacheTTL', 600)
|
||||
@UseInterceptors(HttpCacheInterceptor)
|
||||
async findAll(): Promise<User[]> {
|
||||
return this.usersService.findAll();
|
||||
}
|
||||
|
||||
// Error mapping interceptor
|
||||
@Injectable()
|
||||
export class ErrorMappingInterceptor implements NestInterceptor {
|
||||
intercept(context: ExecutionContext, next: CallHandler): Observable<any> {
|
||||
return next.handle().pipe(
|
||||
catchError((error) => {
|
||||
if (error instanceof EntityNotFoundError) {
|
||||
throw new NotFoundException(error.message);
|
||||
}
|
||||
if (error instanceof QueryFailedError) {
|
||||
if (error.message.includes('duplicate')) {
|
||||
throw new ConflictException('Resource already exists');
|
||||
}
|
||||
}
|
||||
throw error;
|
||||
}),
|
||||
);
|
||||
}
|
||||
}
|
||||
```
|
||||
|
||||
Reference: [NestJS Interceptors](https://docs.nestjs.com/interceptors)
|
||||
@@ -0,0 +1,205 @@
|
||||
---
|
||||
title: Use Pipes for Input Transformation
|
||||
impact: MEDIUM
|
||||
impactDescription: Pipes ensure clean, validated data reaches your handlers
|
||||
tags: api, pipes, validation, transformation
|
||||
---
|
||||
|
||||
## Use Pipes for Input Transformation
|
||||
|
||||
Use built-in pipes like `ParseIntPipe`, `ParseUUIDPipe`, and `DefaultValuePipe` for common transformations. Create custom pipes for business-specific transformations. Pipes separate validation/transformation logic from controllers.
|
||||
|
||||
**Incorrect (manual type parsing in handlers):**
|
||||
|
||||
```typescript
|
||||
// Manual type parsing in handlers
|
||||
@Controller('users')
|
||||
export class UsersController {
|
||||
@Get(':id')
|
||||
async findOne(@Param('id') id: string): Promise<User> {
|
||||
// Manual validation in every handler
|
||||
const uuid = id.trim();
|
||||
if (!isUUID(uuid)) {
|
||||
throw new BadRequestException('Invalid UUID');
|
||||
}
|
||||
return this.usersService.findOne(uuid);
|
||||
}
|
||||
|
||||
@Get()
|
||||
async findAll(
|
||||
@Query('page') page: string,
|
||||
@Query('limit') limit: string,
|
||||
): Promise<User[]> {
|
||||
// Manual parsing and defaults
|
||||
const pageNum = parseInt(page) || 1;
|
||||
const limitNum = parseInt(limit) || 10;
|
||||
return this.usersService.findAll(pageNum, limitNum);
|
||||
}
|
||||
}
|
||||
|
||||
// Type coercion without validation
|
||||
@Get()
|
||||
async search(@Query('price') price: string): Promise<Product[]> {
|
||||
const priceNum = +price; // NaN if invalid, no error
|
||||
return this.productsService.findByPrice(priceNum);
|
||||
}
|
||||
```
|
||||
|
||||
**Correct (use built-in and custom pipes):**
|
||||
|
||||
```typescript
|
||||
// Use built-in pipes for common transformations
|
||||
@Controller('users')
|
||||
export class UsersController {
|
||||
@Get(':id')
|
||||
async findOne(@Param('id', ParseUUIDPipe) id: string): Promise<User> {
|
||||
// id is guaranteed to be a valid UUID
|
||||
return this.usersService.findOne(id);
|
||||
}
|
||||
|
||||
@Get()
|
||||
async findAll(
|
||||
@Query('page', new DefaultValuePipe(1), ParseIntPipe) page: number,
|
||||
@Query('limit', new DefaultValuePipe(10), ParseIntPipe) limit: number,
|
||||
): Promise<User[]> {
|
||||
// Automatic defaults and type conversion
|
||||
return this.usersService.findAll(page, limit);
|
||||
}
|
||||
|
||||
@Get('by-status/:status')
|
||||
async findByStatus(
|
||||
@Param('status', new ParseEnumPipe(UserStatus)) status: UserStatus,
|
||||
): Promise<User[]> {
|
||||
return this.usersService.findByStatus(status);
|
||||
}
|
||||
}
|
||||
|
||||
// Custom pipe for business logic
|
||||
@Injectable()
|
||||
export class ParseDatePipe implements PipeTransform<string, Date> {
|
||||
transform(value: string): Date {
|
||||
const date = new Date(value);
|
||||
if (isNaN(date.getTime())) {
|
||||
throw new BadRequestException('Invalid date format');
|
||||
}
|
||||
return date;
|
||||
}
|
||||
}
|
||||
|
||||
@Get('reports')
|
||||
async getReports(
|
||||
@Query('from', ParseDatePipe) from: Date,
|
||||
@Query('to', ParseDatePipe) to: Date,
|
||||
): Promise<Report[]> {
|
||||
return this.reportsService.findBetween(from, to);
|
||||
}
|
||||
|
||||
// Custom transformation pipes
|
||||
@Injectable()
|
||||
export class NormalizeEmailPipe implements PipeTransform<string, string> {
|
||||
transform(value: string): string {
|
||||
if (!value) return value;
|
||||
return value.trim().toLowerCase();
|
||||
}
|
||||
}
|
||||
|
||||
// Parse comma-separated values
|
||||
@Injectable()
|
||||
export class ParseArrayPipe implements PipeTransform<string, string[]> {
|
||||
transform(value: string): string[] {
|
||||
if (!value) return [];
|
||||
return value.split(',').map((v) => v.trim()).filter(Boolean);
|
||||
}
|
||||
}
|
||||
|
||||
@Get('products')
|
||||
async findProducts(
|
||||
@Query('ids', ParseArrayPipe) ids: string[],
|
||||
@Query('email', NormalizeEmailPipe) email: string,
|
||||
): Promise<Product[]> {
|
||||
// ids is already an array, email is normalized
|
||||
return this.productsService.findByIds(ids);
|
||||
}
|
||||
|
||||
// Sanitize HTML input
|
||||
@Injectable()
|
||||
export class SanitizeHtmlPipe implements PipeTransform<string, string> {
|
||||
transform(value: string): string {
|
||||
if (!value) return value;
|
||||
return sanitizeHtml(value, { allowedTags: [] });
|
||||
}
|
||||
}
|
||||
|
||||
// Global validation pipe with transformation
|
||||
app.useGlobalPipes(
|
||||
new ValidationPipe({
|
||||
whitelist: true, // Strip non-DTO properties
|
||||
transform: true, // Auto-transform to DTO types
|
||||
transformOptions: {
|
||||
enableImplicitConversion: true, // Convert query strings to numbers
|
||||
},
|
||||
forbidNonWhitelisted: true, // Throw on extra properties
|
||||
}),
|
||||
);
|
||||
|
||||
// DTO with transformation decorators
|
||||
export class FindProductsDto {
|
||||
@IsOptional()
|
||||
@Type(() => Number)
|
||||
@IsInt()
|
||||
@Min(1)
|
||||
page?: number = 1;
|
||||
|
||||
@IsOptional()
|
||||
@Type(() => Number)
|
||||
@IsInt()
|
||||
@Min(1)
|
||||
@Max(100)
|
||||
limit?: number = 10;
|
||||
|
||||
@IsOptional()
|
||||
@Transform(({ value }) => value?.toLowerCase())
|
||||
@IsString()
|
||||
search?: string;
|
||||
|
||||
@IsOptional()
|
||||
@Transform(({ value }) => value?.split(','))
|
||||
@IsArray()
|
||||
@IsString({ each: true })
|
||||
categories?: string[];
|
||||
}
|
||||
|
||||
@Get()
|
||||
async findAll(@Query() dto: FindProductsDto): Promise<Product[]> {
|
||||
// dto is already transformed and validated
|
||||
return this.productsService.findAll(dto);
|
||||
}
|
||||
|
||||
// Pipe error customization
|
||||
@Injectable()
|
||||
export class CustomParseIntPipe extends ParseIntPipe {
|
||||
constructor() {
|
||||
super({
|
||||
exceptionFactory: (error) =>
|
||||
new BadRequestException(`${error} must be a valid integer`),
|
||||
});
|
||||
}
|
||||
}
|
||||
|
||||
// Or use options on built-in pipes
|
||||
@Get(':id')
|
||||
async findOne(
|
||||
@Param(
|
||||
'id',
|
||||
new ParseIntPipe({
|
||||
errorHttpStatusCode: HttpStatus.NOT_ACCEPTABLE,
|
||||
exceptionFactory: () => new NotAcceptableException('ID must be numeric'),
|
||||
}),
|
||||
)
|
||||
id: number,
|
||||
): Promise<Item> {
|
||||
return this.itemsService.findOne(id);
|
||||
}
|
||||
```
|
||||
|
||||
Reference: [NestJS Pipes](https://docs.nestjs.com/pipes)
|
||||
@@ -0,0 +1,191 @@
|
||||
---
|
||||
title: Use API Versioning for Breaking Changes
|
||||
impact: MEDIUM
|
||||
impactDescription: Versioning allows you to evolve APIs without breaking existing clients
|
||||
tags: api, versioning, breaking-changes, compatibility
|
||||
---
|
||||
|
||||
## Use API Versioning for Breaking Changes
|
||||
|
||||
Use NestJS built-in versioning when making breaking changes to your API. Choose a versioning strategy (URI, header, or media type) and apply it consistently. This allows old clients to continue working while new clients use updated endpoints.
|
||||
|
||||
**Incorrect (breaking changes without versioning):**
|
||||
|
||||
```typescript
|
||||
// Breaking changes without versioning
|
||||
@Controller('users')
|
||||
export class UsersController {
|
||||
@Get(':id')
|
||||
async findOne(@Param('id') id: string): Promise<User> {
|
||||
// Original response: { id, name, email }
|
||||
// Later changed to: { id, firstName, lastName, emailAddress }
|
||||
// Old clients break!
|
||||
return this.usersService.findOne(id);
|
||||
}
|
||||
}
|
||||
|
||||
// Manual versioning in routes
|
||||
@Controller('v1/users')
|
||||
export class UsersV1Controller {}
|
||||
|
||||
@Controller('v2/users')
|
||||
export class UsersV2Controller {}
|
||||
// Inconsistent, error-prone, hard to maintain
|
||||
```
|
||||
|
||||
**Correct (use NestJS built-in versioning):**
|
||||
|
||||
```typescript
|
||||
// Enable versioning in main.ts
|
||||
async function bootstrap() {
|
||||
const app = await NestFactory.create(AppModule);
|
||||
|
||||
// URI versioning: /v1/users, /v2/users
|
||||
app.enableVersioning({
|
||||
type: VersioningType.URI,
|
||||
defaultVersion: '1',
|
||||
});
|
||||
|
||||
// Or header versioning: X-API-Version: 1
|
||||
app.enableVersioning({
|
||||
type: VersioningType.HEADER,
|
||||
header: 'X-API-Version',
|
||||
defaultVersion: '1',
|
||||
});
|
||||
|
||||
// Or media type: Accept: application/json;v=1
|
||||
app.enableVersioning({
|
||||
type: VersioningType.MEDIA_TYPE,
|
||||
key: 'v=',
|
||||
defaultVersion: '1',
|
||||
});
|
||||
|
||||
await app.listen(3000);
|
||||
}
|
||||
|
||||
// Version-specific controllers
|
||||
@Controller('users')
|
||||
@Version('1')
|
||||
export class UsersV1Controller {
|
||||
@Get(':id')
|
||||
async findOne(@Param('id') id: string): Promise<UserV1Response> {
|
||||
const user = await this.usersService.findOne(id);
|
||||
// V1 response format
|
||||
return {
|
||||
id: user.id,
|
||||
name: user.name,
|
||||
email: user.email,
|
||||
};
|
||||
}
|
||||
}
|
||||
|
||||
@Controller('users')
|
||||
@Version('2')
|
||||
export class UsersV2Controller {
|
||||
@Get(':id')
|
||||
async findOne(@Param('id') id: string): Promise<UserV2Response> {
|
||||
const user = await this.usersService.findOne(id);
|
||||
// V2 response format with breaking changes
|
||||
return {
|
||||
id: user.id,
|
||||
firstName: user.firstName,
|
||||
lastName: user.lastName,
|
||||
emailAddress: user.email,
|
||||
createdAt: user.createdAt,
|
||||
};
|
||||
}
|
||||
}
|
||||
|
||||
// Per-route versioning - different versions for different routes
|
||||
@Controller('users')
|
||||
export class UsersController {
|
||||
@Get()
|
||||
@Version('1')
|
||||
findAllV1(): Promise<UserV1Response[]> {
|
||||
return this.usersService.findAllV1();
|
||||
}
|
||||
|
||||
@Get()
|
||||
@Version('2')
|
||||
findAllV2(): Promise<UserV2Response[]> {
|
||||
return this.usersService.findAllV2();
|
||||
}
|
||||
|
||||
@Get(':id')
|
||||
@Version(['1', '2']) // Same handler for multiple versions
|
||||
findOne(@Param('id') id: string): Promise<User> {
|
||||
return this.usersService.findOne(id);
|
||||
}
|
||||
|
||||
@Post()
|
||||
@Version(VERSION_NEUTRAL) // Available in all versions
|
||||
create(@Body() dto: CreateUserDto): Promise<User> {
|
||||
return this.usersService.create(dto);
|
||||
}
|
||||
}
|
||||
|
||||
// Shared service with version-specific logic
|
||||
@Injectable()
|
||||
export class UsersService {
|
||||
async findOne(id: string, version: string): Promise<any> {
|
||||
const user = await this.repo.findOne({ where: { id } });
|
||||
|
||||
if (version === '1') {
|
||||
return this.toV1Response(user);
|
||||
}
|
||||
return this.toV2Response(user);
|
||||
}
|
||||
|
||||
private toV1Response(user: User): UserV1Response {
|
||||
return {
|
||||
id: user.id,
|
||||
name: `${user.firstName} ${user.lastName}`,
|
||||
email: user.email,
|
||||
};
|
||||
}
|
||||
|
||||
private toV2Response(user: User): UserV2Response {
|
||||
return {
|
||||
id: user.id,
|
||||
firstName: user.firstName,
|
||||
lastName: user.lastName,
|
||||
emailAddress: user.email,
|
||||
createdAt: user.createdAt,
|
||||
};
|
||||
}
|
||||
}
|
||||
|
||||
// Controller extracts version
|
||||
@Controller('users')
|
||||
export class UsersController {
|
||||
@Get(':id')
|
||||
async findOne(
|
||||
@Param('id') id: string,
|
||||
@Headers('X-API-Version') version: string = '1',
|
||||
): Promise<any> {
|
||||
return this.usersService.findOne(id, version);
|
||||
}
|
||||
}
|
||||
|
||||
// Deprecation strategy - mark old versions as deprecated
|
||||
@Controller('users')
|
||||
@Version('1')
|
||||
@UseInterceptors(DeprecationInterceptor)
|
||||
export class UsersV1Controller {
|
||||
// All V1 routes will include deprecation warning
|
||||
}
|
||||
|
||||
@Injectable()
|
||||
export class DeprecationInterceptor implements NestInterceptor {
|
||||
intercept(context: ExecutionContext, next: CallHandler): Observable<any> {
|
||||
const response = context.switchToHttp().getResponse();
|
||||
response.setHeader('Deprecation', 'true');
|
||||
response.setHeader('Sunset', 'Sat, 1 Jan 2025 00:00:00 GMT');
|
||||
response.setHeader('Link', '</v2/users>; rel="successor-version"');
|
||||
|
||||
return next.handle();
|
||||
}
|
||||
}
|
||||
```
|
||||
|
||||
Reference: [NestJS Versioning](https://docs.nestjs.com/techniques/versioning)
|
||||
@@ -0,0 +1,80 @@
|
||||
---
|
||||
title: Avoid Circular Dependencies
|
||||
impact: CRITICAL
|
||||
impactDescription: "#1 cause of runtime crashes"
|
||||
tags: architecture, modules, dependencies
|
||||
---
|
||||
|
||||
## Avoid Circular Dependencies
|
||||
|
||||
Circular dependencies occur when Module A imports Module B, and Module B imports Module A (directly or transitively). NestJS can sometimes resolve these through forward references, but they indicate architectural problems and should be avoided. This is the #1 cause of runtime crashes in NestJS applications.
|
||||
|
||||
**Incorrect (circular module imports):**
|
||||
|
||||
```typescript
|
||||
// users.module.ts
|
||||
@Module({
|
||||
imports: [OrdersModule], // Orders needs Users, Users needs Orders = circular
|
||||
providers: [UsersService],
|
||||
exports: [UsersService],
|
||||
})
|
||||
export class UsersModule {}
|
||||
|
||||
// orders.module.ts
|
||||
@Module({
|
||||
imports: [UsersModule], // Circular dependency!
|
||||
providers: [OrdersService],
|
||||
exports: [OrdersService],
|
||||
})
|
||||
export class OrdersModule {}
|
||||
```
|
||||
|
||||
**Correct (extract shared logic or use events):**
|
||||
|
||||
```typescript
|
||||
// Option 1: Extract shared logic to a third module
|
||||
// shared.module.ts
|
||||
@Module({
|
||||
providers: [SharedService],
|
||||
exports: [SharedService],
|
||||
})
|
||||
export class SharedModule {}
|
||||
|
||||
// users.module.ts
|
||||
@Module({
|
||||
imports: [SharedModule],
|
||||
providers: [UsersService],
|
||||
})
|
||||
export class UsersModule {}
|
||||
|
||||
// orders.module.ts
|
||||
@Module({
|
||||
imports: [SharedModule],
|
||||
providers: [OrdersService],
|
||||
})
|
||||
export class OrdersModule {}
|
||||
|
||||
// Option 2: Use events for decoupled communication
|
||||
// users.service.ts
|
||||
@Injectable()
|
||||
export class UsersService {
|
||||
constructor(private eventEmitter: EventEmitter2) {}
|
||||
|
||||
async createUser(data: CreateUserDto) {
|
||||
const user = await this.userRepo.save(data);
|
||||
this.eventEmitter.emit('user.created', user);
|
||||
return user;
|
||||
}
|
||||
}
|
||||
|
||||
// orders.service.ts
|
||||
@Injectable()
|
||||
export class OrdersService {
|
||||
@OnEvent('user.created')
|
||||
handleUserCreated(user: User) {
|
||||
// React to user creation without direct dependency
|
||||
}
|
||||
}
|
||||
```
|
||||
|
||||
Reference: [NestJS Circular Dependency](https://docs.nestjs.com/fundamentals/circular-dependency)
|
||||
@@ -0,0 +1,82 @@
|
||||
---
|
||||
title: Organize by Feature Modules
|
||||
impact: CRITICAL
|
||||
impactDescription: "3-5x faster onboarding and development"
|
||||
tags: architecture, modules, organization
|
||||
---
|
||||
|
||||
## Organize by Feature Modules
|
||||
|
||||
Organize your application into feature modules that encapsulate related functionality. Each feature module should be self-contained with its own controllers, services, entities, and DTOs. Avoid organizing by technical layer (all controllers together, all services together). This enables 3-5x faster onboarding and feature development.
|
||||
|
||||
**Incorrect (technical layer organization):**
|
||||
|
||||
```typescript
|
||||
// Technical layer organization (anti-pattern)
|
||||
src/
|
||||
├── controllers/
|
||||
│ ├── users.controller.ts
|
||||
│ ├── orders.controller.ts
|
||||
│ └── products.controller.ts
|
||||
├── services/
|
||||
│ ├── users.service.ts
|
||||
│ ├── orders.service.ts
|
||||
│ └── products.service.ts
|
||||
├── entities/
|
||||
│ ├── user.entity.ts
|
||||
│ ├── order.entity.ts
|
||||
│ └── product.entity.ts
|
||||
└── app.module.ts // Imports everything directly
|
||||
```
|
||||
|
||||
**Correct (feature module organization):**
|
||||
|
||||
```typescript
|
||||
// Feature module organization
|
||||
src/
|
||||
├── users/
|
||||
│ ├── dto/
|
||||
│ │ ├── create-user.dto.ts
|
||||
│ │ └── update-user.dto.ts
|
||||
│ ├── entities/
|
||||
│ │ └── user.entity.ts
|
||||
│ ├── users.controller.ts
|
||||
│ ├── users.service.ts
|
||||
│ ├── users.repository.ts
|
||||
│ └── users.module.ts
|
||||
├── orders/
|
||||
│ ├── dto/
|
||||
│ ├── entities/
|
||||
│ ├── orders.controller.ts
|
||||
│ ├── orders.service.ts
|
||||
│ └── orders.module.ts
|
||||
├── shared/
|
||||
│ ├── guards/
|
||||
│ ├── interceptors/
|
||||
│ ├── filters/
|
||||
│ └── shared.module.ts
|
||||
└── app.module.ts
|
||||
|
||||
// users.module.ts
|
||||
@Module({
|
||||
imports: [TypeOrmModule.forFeature([User])],
|
||||
controllers: [UsersController],
|
||||
providers: [UsersService, UsersRepository],
|
||||
exports: [UsersService], // Only export what others need
|
||||
})
|
||||
export class UsersModule {}
|
||||
|
||||
// app.module.ts
|
||||
@Module({
|
||||
imports: [
|
||||
ConfigModule.forRoot(),
|
||||
TypeOrmModule.forRoot(),
|
||||
UsersModule,
|
||||
OrdersModule,
|
||||
SharedModule,
|
||||
],
|
||||
})
|
||||
export class AppModule {}
|
||||
```
|
||||
|
||||
Reference: [NestJS Modules](https://docs.nestjs.com/modules)
|
||||
@@ -0,0 +1,141 @@
|
||||
---
|
||||
title: Use Proper Module Sharing Patterns
|
||||
impact: CRITICAL
|
||||
impactDescription: Prevents duplicate instances, memory leaks, and state inconsistency
|
||||
tags: architecture, modules, sharing, exports
|
||||
---
|
||||
|
||||
## Use Proper Module Sharing Patterns
|
||||
|
||||
NestJS modules are singletons by default. When a service is properly exported from a module and that module is imported elsewhere, the same instance is shared. However, providing a service in multiple modules creates separate instances, leading to memory waste, state inconsistency, and confusing behavior. Always encapsulate services in dedicated modules, export them explicitly, and import the module where needed.
|
||||
|
||||
**Incorrect (service provided in multiple modules):**
|
||||
|
||||
```typescript
|
||||
// StorageService provided directly in multiple modules - WRONG
|
||||
// storage.service.ts
|
||||
@Injectable()
|
||||
export class StorageService {
|
||||
private cache = new Map(); // Each instance has separate state!
|
||||
|
||||
store(key: string, value: any) {
|
||||
this.cache.set(key, value);
|
||||
}
|
||||
}
|
||||
|
||||
// app.module.ts
|
||||
@Module({
|
||||
providers: [StorageService], // Instance #1
|
||||
controllers: [AppController],
|
||||
})
|
||||
export class AppModule {}
|
||||
|
||||
// videos.module.ts
|
||||
@Module({
|
||||
providers: [StorageService], // Instance #2 - different from AppModule!
|
||||
controllers: [VideosController],
|
||||
})
|
||||
export class VideosModule {}
|
||||
|
||||
// Problems:
|
||||
// 1. Two separate StorageService instances exist
|
||||
// 2. cache.set() in VideosModule doesn't affect AppModule's cache
|
||||
// 3. Memory wasted on duplicate instances
|
||||
// 4. Debugging nightmares when state doesn't sync
|
||||
```
|
||||
|
||||
**Correct (dedicated module with exports):**
|
||||
|
||||
```typescript
|
||||
// storage/storage.module.ts
|
||||
@Module({
|
||||
providers: [StorageService],
|
||||
exports: [StorageService], // Make available to importers
|
||||
})
|
||||
export class StorageModule {}
|
||||
|
||||
// videos/videos.module.ts
|
||||
@Module({
|
||||
imports: [StorageModule], // Import the module, not the service
|
||||
controllers: [VideosController],
|
||||
providers: [VideosService],
|
||||
})
|
||||
export class VideosModule {}
|
||||
|
||||
// channels/channels.module.ts
|
||||
@Module({
|
||||
imports: [StorageModule], // Same instance shared
|
||||
controllers: [ChannelsController],
|
||||
providers: [ChannelsService],
|
||||
})
|
||||
export class ChannelsModule {}
|
||||
|
||||
// app.module.ts
|
||||
@Module({
|
||||
imports: [
|
||||
StorageModule, // Only if AppModule itself needs StorageService
|
||||
VideosModule,
|
||||
ChannelsModule,
|
||||
],
|
||||
})
|
||||
export class AppModule {}
|
||||
|
||||
// Now all modules share the SAME StorageService instance
|
||||
```
|
||||
|
||||
**When to use @Global() (sparingly):**
|
||||
|
||||
```typescript
|
||||
// ONLY for truly cross-cutting concerns
|
||||
@Global()
|
||||
@Module({
|
||||
providers: [ConfigService, LoggerService],
|
||||
exports: [ConfigService, LoggerService],
|
||||
})
|
||||
export class CoreModule {}
|
||||
|
||||
// Import once in AppModule
|
||||
@Module({
|
||||
imports: [CoreModule], // Registered globally, available everywhere
|
||||
})
|
||||
export class AppModule {}
|
||||
|
||||
// Other modules don't need to import CoreModule
|
||||
@Module({
|
||||
controllers: [UsersController],
|
||||
providers: [UsersService], // Can inject ConfigService without importing
|
||||
})
|
||||
export class UsersModule {}
|
||||
|
||||
// WARNING: Don't make everything global!
|
||||
// - Hides dependencies (can't see what a module needs from imports)
|
||||
// - Makes testing harder
|
||||
// - Reserve for: config, logging, database connections
|
||||
```
|
||||
|
||||
**Module re-exporting pattern:**
|
||||
|
||||
```typescript
|
||||
// common.module.ts - shared utilities
|
||||
@Module({
|
||||
providers: [DateService, ValidationService],
|
||||
exports: [DateService, ValidationService],
|
||||
})
|
||||
export class CommonModule {}
|
||||
|
||||
// core.module.ts - re-exports common for convenience
|
||||
@Module({
|
||||
imports: [CommonModule, DatabaseModule],
|
||||
exports: [CommonModule, DatabaseModule], // Re-export for consumers
|
||||
})
|
||||
export class CoreModule {}
|
||||
|
||||
// feature.module.ts - imports CoreModule, gets both
|
||||
@Module({
|
||||
imports: [CoreModule], // Gets CommonModule + DatabaseModule
|
||||
controllers: [FeatureController],
|
||||
})
|
||||
export class FeatureModule {}
|
||||
```
|
||||
|
||||
Reference: [NestJS Modules](https://docs.nestjs.com/modules#shared-modules)
|
||||
@@ -0,0 +1,106 @@
|
||||
---
|
||||
title: Single Responsibility for Services
|
||||
impact: CRITICAL
|
||||
impactDescription: "40%+ improvement in testability"
|
||||
tags: architecture, services, single-responsibility
|
||||
---
|
||||
|
||||
## Single Responsibility for Services
|
||||
|
||||
Each service should have a single, well-defined responsibility. Avoid "god services" that handle multiple unrelated concerns. If a service name includes "And" or handles more than one domain concept, it likely violates single responsibility. This reduces complexity and improves testability by 40%+.
|
||||
|
||||
**Incorrect (god service anti-pattern):**
|
||||
|
||||
```typescript
|
||||
// God service anti-pattern
|
||||
@Injectable()
|
||||
export class UserAndOrderService {
|
||||
constructor(
|
||||
private userRepo: UserRepository,
|
||||
private orderRepo: OrderRepository,
|
||||
private mailer: MailService,
|
||||
private payment: PaymentService,
|
||||
) {}
|
||||
|
||||
async createUser(dto: CreateUserDto) {
|
||||
const user = await this.userRepo.save(dto);
|
||||
await this.mailer.sendWelcome(user);
|
||||
return user;
|
||||
}
|
||||
|
||||
async createOrder(userId: string, dto: CreateOrderDto) {
|
||||
const order = await this.orderRepo.save({ userId, ...dto });
|
||||
await this.payment.charge(order);
|
||||
await this.mailer.sendOrderConfirmation(order);
|
||||
return order;
|
||||
}
|
||||
|
||||
async calculateOrderStats(userId: string) {
|
||||
// Stats logic mixed in
|
||||
}
|
||||
|
||||
async validatePayment(orderId: string) {
|
||||
// Payment logic mixed in
|
||||
}
|
||||
}
|
||||
```
|
||||
|
||||
**Correct (focused services with single responsibility):**
|
||||
|
||||
```typescript
|
||||
// Focused services with single responsibility
|
||||
@Injectable()
|
||||
export class UsersService {
|
||||
constructor(private userRepo: UserRepository) {}
|
||||
|
||||
async create(dto: CreateUserDto): Promise<User> {
|
||||
return this.userRepo.save(dto);
|
||||
}
|
||||
|
||||
async findById(id: string): Promise<User> {
|
||||
return this.userRepo.findOneOrFail({ where: { id } });
|
||||
}
|
||||
}
|
||||
|
||||
@Injectable()
|
||||
export class OrdersService {
|
||||
constructor(private orderRepo: OrderRepository) {}
|
||||
|
||||
async create(userId: string, dto: CreateOrderDto): Promise<Order> {
|
||||
return this.orderRepo.save({ userId, ...dto });
|
||||
}
|
||||
|
||||
async findByUser(userId: string): Promise<Order[]> {
|
||||
return this.orderRepo.find({ where: { userId } });
|
||||
}
|
||||
}
|
||||
|
||||
@Injectable()
|
||||
export class OrderStatsService {
|
||||
constructor(private orderRepo: OrderRepository) {}
|
||||
|
||||
async calculateForUser(userId: string): Promise<OrderStats> {
|
||||
// Focused stats calculation
|
||||
}
|
||||
}
|
||||
|
||||
// Orchestration in controller or dedicated orchestrator
|
||||
@Controller('orders')
|
||||
export class OrdersController {
|
||||
constructor(
|
||||
private orders: OrdersService,
|
||||
private payment: PaymentService,
|
||||
private notifications: NotificationService,
|
||||
) {}
|
||||
|
||||
@Post()
|
||||
async create(@CurrentUser() user: User, @Body() dto: CreateOrderDto) {
|
||||
const order = await this.orders.create(user.id, dto);
|
||||
await this.payment.charge(order);
|
||||
await this.notifications.sendOrderConfirmation(order);
|
||||
return order;
|
||||
}
|
||||
}
|
||||
```
|
||||
|
||||
Reference: [NestJS Providers](https://docs.nestjs.com/providers)
|
||||
@@ -0,0 +1,108 @@
|
||||
---
|
||||
title: Use Event-Driven Architecture for Decoupling
|
||||
impact: MEDIUM-HIGH
|
||||
impactDescription: Enables async processing and modularity
|
||||
tags: architecture, events, decoupling
|
||||
---
|
||||
|
||||
## Use Event-Driven Architecture for Decoupling
|
||||
|
||||
Use `@nestjs/event-emitter` for intra-service events and message brokers for inter-service communication. Events allow modules to react to changes without direct dependencies, improving modularity and enabling async processing.
|
||||
|
||||
**Incorrect (direct service coupling):**
|
||||
|
||||
```typescript
|
||||
// Direct service coupling
|
||||
@Injectable()
|
||||
export class OrdersService {
|
||||
constructor(
|
||||
private inventoryService: InventoryService,
|
||||
private emailService: EmailService,
|
||||
private analyticsService: AnalyticsService,
|
||||
private notificationService: NotificationService,
|
||||
private loyaltyService: LoyaltyService,
|
||||
) {}
|
||||
|
||||
async createOrder(dto: CreateOrderDto): Promise<Order> {
|
||||
const order = await this.repo.save(dto);
|
||||
|
||||
// Tight coupling - OrdersService knows about all consumers
|
||||
await this.inventoryService.reserve(order.items);
|
||||
await this.emailService.sendConfirmation(order);
|
||||
await this.analyticsService.track('order_created', order);
|
||||
await this.notificationService.push(order.userId, 'Order placed');
|
||||
await this.loyaltyService.addPoints(order.userId, order.total);
|
||||
|
||||
// Adding new behavior requires modifying this service
|
||||
return order;
|
||||
}
|
||||
}
|
||||
```
|
||||
|
||||
**Correct (event-driven decoupling):**
|
||||
|
||||
```typescript
|
||||
// Use EventEmitter for decoupling
|
||||
import { EventEmitter2 } from '@nestjs/event-emitter';
|
||||
|
||||
// Define event
|
||||
export class OrderCreatedEvent {
|
||||
constructor(
|
||||
public readonly orderId: string,
|
||||
public readonly userId: string,
|
||||
public readonly items: OrderItem[],
|
||||
public readonly total: number,
|
||||
) {}
|
||||
}
|
||||
|
||||
// Service emits events
|
||||
@Injectable()
|
||||
export class OrdersService {
|
||||
constructor(
|
||||
private eventEmitter: EventEmitter2,
|
||||
private repo: Repository<Order>,
|
||||
) {}
|
||||
|
||||
async createOrder(dto: CreateOrderDto): Promise<Order> {
|
||||
const order = await this.repo.save(dto);
|
||||
|
||||
// Emit event - no knowledge of consumers
|
||||
this.eventEmitter.emit(
|
||||
'order.created',
|
||||
new OrderCreatedEvent(order.id, order.userId, order.items, order.total),
|
||||
);
|
||||
|
||||
return order;
|
||||
}
|
||||
}
|
||||
|
||||
// Listeners in separate modules
|
||||
@Injectable()
|
||||
export class InventoryListener {
|
||||
@OnEvent('order.created')
|
||||
async handleOrderCreated(event: OrderCreatedEvent): Promise<void> {
|
||||
await this.inventoryService.reserve(event.items);
|
||||
}
|
||||
}
|
||||
|
||||
@Injectable()
|
||||
export class EmailListener {
|
||||
@OnEvent('order.created')
|
||||
async handleOrderCreated(event: OrderCreatedEvent): Promise<void> {
|
||||
await this.emailService.sendConfirmation(event.orderId);
|
||||
}
|
||||
}
|
||||
|
||||
@Injectable()
|
||||
export class AnalyticsListener {
|
||||
@OnEvent('order.created')
|
||||
async handleOrderCreated(event: OrderCreatedEvent): Promise<void> {
|
||||
await this.analyticsService.track('order_created', {
|
||||
orderId: event.orderId,
|
||||
total: event.total,
|
||||
});
|
||||
}
|
||||
}
|
||||
```
|
||||
|
||||
Reference: [NestJS Events](https://docs.nestjs.com/techniques/events)
|
||||
@@ -0,0 +1,97 @@
|
||||
---
|
||||
title: Use Repository Pattern for Data Access
|
||||
impact: HIGH
|
||||
impactDescription: Decouples business logic from database
|
||||
tags: architecture, repository, data-access
|
||||
---
|
||||
|
||||
## Use Repository Pattern for Data Access
|
||||
|
||||
Create custom repositories to encapsulate complex queries and database logic. This keeps services focused on business logic, makes testing easier with mock repositories, and allows changing database implementations without affecting business code.
|
||||
|
||||
**Incorrect (complex queries in services):**
|
||||
|
||||
```typescript
|
||||
// Complex queries in services
|
||||
@Injectable()
|
||||
export class UsersService {
|
||||
constructor(
|
||||
@InjectRepository(User) private repo: Repository<User>,
|
||||
) {}
|
||||
|
||||
async findActiveWithOrders(minOrders: number): Promise<User[]> {
|
||||
// Complex query logic mixed with business logic
|
||||
return this.repo
|
||||
.createQueryBuilder('user')
|
||||
.leftJoinAndSelect('user.orders', 'order')
|
||||
.where('user.isActive = :active', { active: true })
|
||||
.andWhere('user.deletedAt IS NULL')
|
||||
.groupBy('user.id')
|
||||
.having('COUNT(order.id) >= :min', { min: minOrders })
|
||||
.orderBy('user.createdAt', 'DESC')
|
||||
.getMany();
|
||||
}
|
||||
|
||||
// Service becomes bloated with query logic
|
||||
}
|
||||
```
|
||||
|
||||
**Correct (custom repository with encapsulated queries):**
|
||||
|
||||
```typescript
|
||||
// Custom repository with encapsulated queries
|
||||
@Injectable()
|
||||
export class UsersRepository {
|
||||
constructor(
|
||||
@InjectRepository(User) private repo: Repository<User>,
|
||||
) {}
|
||||
|
||||
async findById(id: string): Promise<User | null> {
|
||||
return this.repo.findOne({ where: { id } });
|
||||
}
|
||||
|
||||
async findByEmail(email: string): Promise<User | null> {
|
||||
return this.repo.findOne({ where: { email } });
|
||||
}
|
||||
|
||||
async findActiveWithMinOrders(minOrders: number): Promise<User[]> {
|
||||
return this.repo
|
||||
.createQueryBuilder('user')
|
||||
.leftJoinAndSelect('user.orders', 'order')
|
||||
.where('user.isActive = :active', { active: true })
|
||||
.andWhere('user.deletedAt IS NULL')
|
||||
.groupBy('user.id')
|
||||
.having('COUNT(order.id) >= :min', { min: minOrders })
|
||||
.orderBy('user.createdAt', 'DESC')
|
||||
.getMany();
|
||||
}
|
||||
|
||||
async save(user: User): Promise<User> {
|
||||
return this.repo.save(user);
|
||||
}
|
||||
}
|
||||
|
||||
// Clean service with business logic only
|
||||
@Injectable()
|
||||
export class UsersService {
|
||||
constructor(private usersRepo: UsersRepository) {}
|
||||
|
||||
async getActiveUsersWithOrders(): Promise<User[]> {
|
||||
return this.usersRepo.findActiveWithMinOrders(1);
|
||||
}
|
||||
|
||||
async create(dto: CreateUserDto): Promise<User> {
|
||||
const existing = await this.usersRepo.findByEmail(dto.email);
|
||||
if (existing) {
|
||||
throw new ConflictException('Email already registered');
|
||||
}
|
||||
|
||||
const user = new User();
|
||||
user.email = dto.email;
|
||||
user.name = dto.name;
|
||||
return this.usersRepo.save(user);
|
||||
}
|
||||
}
|
||||
```
|
||||
|
||||
Reference: [Repository Pattern](https://martinfowler.com/eaaCatalog/repository.html)
|
||||
@@ -0,0 +1,139 @@
|
||||
---
|
||||
title: Avoid N+1 Query Problems
|
||||
impact: HIGH
|
||||
impactDescription: N+1 queries are one of the most common performance killers
|
||||
tags: database, n-plus-one, queries, performance
|
||||
---
|
||||
|
||||
## Avoid N+1 Query Problems
|
||||
|
||||
N+1 queries occur when you fetch a list of entities, then make an additional query for each entity to load related data. Use eager loading with `relations`, query builder joins, or DataLoader to batch queries efficiently.
|
||||
|
||||
**Incorrect (lazy loading in loops causes N+1):**
|
||||
|
||||
```typescript
|
||||
// Lazy loading in loops causes N+1
|
||||
@Injectable()
|
||||
export class OrdersService {
|
||||
async getOrdersWithItems(userId: string): Promise<Order[]> {
|
||||
const orders = await this.orderRepo.find({ where: { userId } });
|
||||
// 1 query for orders
|
||||
|
||||
for (const order of orders) {
|
||||
// N additional queries - one per order!
|
||||
order.items = await this.itemRepo.find({ where: { orderId: order.id } });
|
||||
}
|
||||
|
||||
return orders;
|
||||
}
|
||||
}
|
||||
|
||||
// Accessing lazy relations without loading
|
||||
@Controller('users')
|
||||
export class UsersController {
|
||||
@Get()
|
||||
async findAll(): Promise<User[]> {
|
||||
const users = await this.userRepo.find();
|
||||
// If User.posts is lazy-loaded, serializing triggers N queries
|
||||
return users; // Each user.posts access = 1 query
|
||||
}
|
||||
}
|
||||
```
|
||||
|
||||
**Correct (use relations for eager loading):**
|
||||
|
||||
```typescript
|
||||
// Use relations option for eager loading
|
||||
@Injectable()
|
||||
export class OrdersService {
|
||||
async getOrdersWithItems(userId: string): Promise<Order[]> {
|
||||
// Single query with JOIN
|
||||
return this.orderRepo.find({
|
||||
where: { userId },
|
||||
relations: ['items', 'items.product'],
|
||||
});
|
||||
}
|
||||
}
|
||||
|
||||
// Use QueryBuilder for complex joins
|
||||
@Injectable()
|
||||
export class UsersService {
|
||||
async getUsersWithPostCounts(): Promise<UserWithPostCount[]> {
|
||||
return this.userRepo
|
||||
.createQueryBuilder('user')
|
||||
.leftJoin('user.posts', 'post')
|
||||
.select('user.id', 'id')
|
||||
.addSelect('user.name', 'name')
|
||||
.addSelect('COUNT(post.id)', 'postCount')
|
||||
.groupBy('user.id')
|
||||
.getRawMany();
|
||||
}
|
||||
|
||||
async getActiveUsersWithPosts(): Promise<User[]> {
|
||||
return this.userRepo
|
||||
.createQueryBuilder('user')
|
||||
.leftJoinAndSelect('user.posts', 'post')
|
||||
.leftJoinAndSelect('post.comments', 'comment')
|
||||
.where('user.isActive = :active', { active: true })
|
||||
.andWhere('post.status = :status', { status: 'published' })
|
||||
.getMany();
|
||||
}
|
||||
}
|
||||
|
||||
// Use find options for specific fields
|
||||
async getOrderSummaries(userId: string): Promise<OrderSummary[]> {
|
||||
return this.orderRepo.find({
|
||||
where: { userId },
|
||||
relations: ['items'],
|
||||
select: {
|
||||
id: true,
|
||||
total: true,
|
||||
status: true,
|
||||
items: {
|
||||
id: true,
|
||||
quantity: true,
|
||||
price: true,
|
||||
},
|
||||
},
|
||||
});
|
||||
}
|
||||
|
||||
// Use DataLoader for GraphQL to batch and cache queries
|
||||
import DataLoader from 'dataloader';
|
||||
|
||||
@Injectable({ scope: Scope.REQUEST })
|
||||
export class PostsLoader {
|
||||
constructor(private postsService: PostsService) {}
|
||||
|
||||
readonly batchPosts = new DataLoader<string, Post[]>(async (userIds) => {
|
||||
// Single query for all users' posts
|
||||
const posts = await this.postsService.findByUserIds([...userIds]);
|
||||
|
||||
// Group by userId
|
||||
const postsMap = new Map<string, Post[]>();
|
||||
for (const post of posts) {
|
||||
const userPosts = postsMap.get(post.userId) || [];
|
||||
userPosts.push(post);
|
||||
postsMap.set(post.userId, userPosts);
|
||||
}
|
||||
|
||||
// Return in same order as input
|
||||
return userIds.map((id) => postsMap.get(id) || []);
|
||||
});
|
||||
}
|
||||
|
||||
// In resolver
|
||||
@ResolveField()
|
||||
async posts(@Parent() user: User): Promise<Post[]> {
|
||||
// DataLoader batches multiple calls into single query
|
||||
return this.postsLoader.batchPosts.load(user.id);
|
||||
}
|
||||
|
||||
// Enable query logging in development to detect N+1
|
||||
TypeOrmModule.forRoot({
|
||||
logging: ['query', 'error'],
|
||||
logger: 'advanced-console',
|
||||
});
|
||||
```
|
||||
|
||||
Reference: [TypeORM Relations](https://typeorm.io/relations)
|
||||
@@ -0,0 +1,61 @@
|
||||
---
|
||||
title: Use Database Migrations
|
||||
impact: HIGH
|
||||
impactDescription: Enables safe, repeatable database schema changes
|
||||
tags: database, migrations, drizzle, schema
|
||||
---
|
||||
|
||||
## Use Database Migrations
|
||||
|
||||
Never push schema changes with `drizzle-kit push` in production. Use versioned SQL migrations for all schema changes. Migrations provide version control for your database, enable safe rollbacks, and ensure consistency across all environments.
|
||||
|
||||
**Incorrect (pushing schema or running ad-hoc SQL):**
|
||||
|
||||
```typescript
|
||||
// drizzle-kit push against production
|
||||
// Mutates the live database with no rollback file
|
||||
|
||||
@Injectable()
|
||||
export class DatabaseService {
|
||||
async addColumn(): Promise<void> {
|
||||
await this.db.execute(sql`ALTER TABLE users ADD COLUMN age INT`);
|
||||
}
|
||||
}
|
||||
```
|
||||
|
||||
**Correct (generate and apply Drizzle migrations):**
|
||||
|
||||
```typescript
|
||||
// drizzle.config.ts
|
||||
import { defineConfig } from 'drizzle-kit';
|
||||
|
||||
export default defineConfig({
|
||||
schema: './drizzle/schema.ts',
|
||||
out: './drizzle/migrations',
|
||||
dialect: 'postgresql',
|
||||
dbCredentials: {
|
||||
url: process.env.DATABASE_URL!,
|
||||
},
|
||||
});
|
||||
```
|
||||
|
||||
```bash
|
||||
# Generate a migration from schema diffs
|
||||
npx drizzle-kit generate
|
||||
|
||||
# Apply migrations
|
||||
npx drizzle-kit migrate
|
||||
```
|
||||
|
||||
```typescript
|
||||
// drizzle/schema.ts
|
||||
export const users = pgTable('users', {
|
||||
id: uuid('id').primaryKey().defaultRandom(),
|
||||
email: varchar('email', { length: 255 }).notNull(),
|
||||
age: integer('age').default(0),
|
||||
});
|
||||
```
|
||||
|
||||
Always keep `down`/rollback SQL when a migration is destructive. Never edit an already-applied migration file; add a new one.
|
||||
|
||||
Reference: [Drizzle Kit Migrations](https://orm.drizzle.team/docs/kit-overview)
|
||||
@@ -0,0 +1,140 @@
|
||||
---
|
||||
title: Use Transactions for Multi-Step Operations
|
||||
impact: HIGH
|
||||
impactDescription: Ensures data consistency in multi-step operations
|
||||
tags: database, transactions, typeorm, consistency
|
||||
---
|
||||
|
||||
## Use Transactions for Multi-Step Operations
|
||||
|
||||
When multiple database operations must succeed or fail together, wrap them in a transaction. This prevents partial updates that leave your data in an inconsistent state. Use TypeORM's transaction APIs or the DataSource query runner for complex scenarios.
|
||||
|
||||
**Incorrect (multiple saves without transaction):**
|
||||
|
||||
```typescript
|
||||
// Multiple saves without transaction
|
||||
@Injectable()
|
||||
export class OrdersService {
|
||||
async createOrder(userId: string, items: OrderItem[]): Promise<Order> {
|
||||
// If any step fails, data is inconsistent
|
||||
const order = await this.orderRepo.save({ userId, status: 'pending' });
|
||||
|
||||
for (const item of items) {
|
||||
await this.orderItemRepo.save({ orderId: order.id, ...item });
|
||||
await this.inventoryRepo.decrement({ productId: item.productId }, 'stock', item.quantity);
|
||||
}
|
||||
|
||||
await this.paymentService.charge(order.id);
|
||||
// If payment fails, order and inventory are already modified!
|
||||
|
||||
return order;
|
||||
}
|
||||
}
|
||||
```
|
||||
|
||||
**Correct (use DataSource.transaction for automatic rollback):**
|
||||
|
||||
```typescript
|
||||
// Use DataSource.transaction() for automatic rollback
|
||||
@Injectable()
|
||||
export class OrdersService {
|
||||
constructor(private dataSource: DataSource) {}
|
||||
|
||||
async createOrder(userId: string, items: OrderItem[]): Promise<Order> {
|
||||
return this.dataSource.transaction(async (manager) => {
|
||||
// All operations use the same transactional manager
|
||||
const order = await manager.save(Order, { userId, status: 'pending' });
|
||||
|
||||
for (const item of items) {
|
||||
await manager.save(OrderItem, { orderId: order.id, ...item });
|
||||
await manager.decrement(
|
||||
Inventory,
|
||||
{ productId: item.productId },
|
||||
'stock',
|
||||
item.quantity,
|
||||
);
|
||||
}
|
||||
|
||||
// If this throws, everything rolls back
|
||||
await this.paymentService.chargeWithManager(manager, order.id);
|
||||
|
||||
return order;
|
||||
});
|
||||
}
|
||||
}
|
||||
|
||||
// QueryRunner for manual transaction control
|
||||
@Injectable()
|
||||
export class TransferService {
|
||||
constructor(private dataSource: DataSource) {}
|
||||
|
||||
async transfer(fromId: string, toId: string, amount: number): Promise<void> {
|
||||
const queryRunner = this.dataSource.createQueryRunner();
|
||||
await queryRunner.connect();
|
||||
await queryRunner.startTransaction();
|
||||
|
||||
try {
|
||||
// Debit source account
|
||||
await queryRunner.manager.decrement(
|
||||
Account,
|
||||
{ id: fromId },
|
||||
'balance',
|
||||
amount,
|
||||
);
|
||||
|
||||
// Verify sufficient funds
|
||||
const source = await queryRunner.manager.findOne(Account, {
|
||||
where: { id: fromId },
|
||||
});
|
||||
if (source.balance < 0) {
|
||||
throw new BadRequestException('Insufficient funds');
|
||||
}
|
||||
|
||||
// Credit destination account
|
||||
await queryRunner.manager.increment(
|
||||
Account,
|
||||
{ id: toId },
|
||||
'balance',
|
||||
amount,
|
||||
);
|
||||
|
||||
// Log the transaction
|
||||
await queryRunner.manager.save(TransactionLog, {
|
||||
fromId,
|
||||
toId,
|
||||
amount,
|
||||
timestamp: new Date(),
|
||||
});
|
||||
|
||||
await queryRunner.commitTransaction();
|
||||
} catch (error) {
|
||||
await queryRunner.rollbackTransaction();
|
||||
throw error;
|
||||
} finally {
|
||||
await queryRunner.release();
|
||||
}
|
||||
}
|
||||
}
|
||||
|
||||
// Repository method with transaction support
|
||||
@Injectable()
|
||||
export class UsersRepository {
|
||||
constructor(
|
||||
@InjectRepository(User) private repo: Repository<User>,
|
||||
private dataSource: DataSource,
|
||||
) {}
|
||||
|
||||
async createWithProfile(
|
||||
userData: CreateUserDto,
|
||||
profileData: CreateProfileDto,
|
||||
): Promise<User> {
|
||||
return this.dataSource.transaction(async (manager) => {
|
||||
const user = await manager.save(User, userData);
|
||||
await manager.save(Profile, { ...profileData, userId: user.id });
|
||||
return user;
|
||||
});
|
||||
}
|
||||
}
|
||||
```
|
||||
|
||||
Reference: [TypeORM Transactions](https://typeorm.io/transactions)
|
||||
@@ -0,0 +1,222 @@
|
||||
---
|
||||
title: Implement Graceful Shutdown
|
||||
impact: MEDIUM-HIGH
|
||||
impactDescription: Proper shutdown handling ensures zero-downtime deployments
|
||||
tags: devops, graceful-shutdown, lifecycle, kubernetes
|
||||
---
|
||||
|
||||
## Implement Graceful Shutdown
|
||||
|
||||
Handle SIGTERM and SIGINT signals to gracefully shutdown your NestJS application. Stop accepting new requests, wait for in-flight requests to complete, close database connections, and clean up resources. This prevents data loss and connection errors during deployments.
|
||||
|
||||
**Incorrect (ignoring shutdown signals):**
|
||||
|
||||
```typescript
|
||||
// Ignore shutdown signals
|
||||
async function bootstrap() {
|
||||
const app = await NestFactory.create(AppModule);
|
||||
await app.listen(3000);
|
||||
// App crashes immediately on SIGTERM
|
||||
// In-flight requests fail
|
||||
// Database connections are abruptly closed
|
||||
}
|
||||
|
||||
// Long-running tasks without cancellation
|
||||
@Injectable()
|
||||
export class ProcessingService {
|
||||
async processLargeFile(file: File): Promise<void> {
|
||||
// No way to interrupt this during shutdown
|
||||
for (let i = 0; i < file.chunks.length; i++) {
|
||||
await this.processChunk(file.chunks[i]);
|
||||
// May run for minutes, blocking shutdown
|
||||
}
|
||||
}
|
||||
}
|
||||
```
|
||||
|
||||
**Correct (enable shutdown hooks and handle cleanup):**
|
||||
|
||||
```typescript
|
||||
// Enable shutdown hooks in main.ts
|
||||
async function bootstrap() {
|
||||
const app = await NestFactory.create(AppModule);
|
||||
|
||||
// Enable shutdown hooks
|
||||
app.enableShutdownHooks();
|
||||
|
||||
// Optional: Add timeout for forced shutdown
|
||||
const server = await app.listen(3000);
|
||||
server.setTimeout(30000); // 30 second timeout
|
||||
|
||||
// Handle graceful shutdown
|
||||
const signals = ['SIGTERM', 'SIGINT'];
|
||||
signals.forEach((signal) => {
|
||||
process.on(signal, async () => {
|
||||
console.log(`Received ${signal}, starting graceful shutdown...`);
|
||||
|
||||
// Stop accepting new connections
|
||||
server.close(async () => {
|
||||
console.log('HTTP server closed');
|
||||
await app.close();
|
||||
process.exit(0);
|
||||
});
|
||||
|
||||
// Force exit after timeout
|
||||
setTimeout(() => {
|
||||
console.error('Forced shutdown after timeout');
|
||||
process.exit(1);
|
||||
}, 30000);
|
||||
});
|
||||
});
|
||||
}
|
||||
|
||||
// Lifecycle hooks for cleanup
|
||||
@Injectable()
|
||||
export class DatabaseService implements OnApplicationShutdown {
|
||||
private readonly connections: Connection[] = [];
|
||||
|
||||
async onApplicationShutdown(signal?: string): Promise<void> {
|
||||
console.log(`Database service shutting down on ${signal}`);
|
||||
|
||||
// Close all connections gracefully
|
||||
await Promise.all(
|
||||
this.connections.map((conn) => conn.close()),
|
||||
);
|
||||
|
||||
console.log('All database connections closed');
|
||||
}
|
||||
}
|
||||
|
||||
// Queue processor with graceful shutdown
|
||||
@Injectable()
|
||||
export class QueueService implements OnApplicationShutdown, OnModuleDestroy {
|
||||
private isShuttingDown = false;
|
||||
|
||||
onModuleDestroy(): void {
|
||||
this.isShuttingDown = true;
|
||||
}
|
||||
|
||||
async onApplicationShutdown(): Promise<void> {
|
||||
// Wait for current jobs to complete
|
||||
await this.queue.close();
|
||||
}
|
||||
|
||||
async processJob(job: Job): Promise<void> {
|
||||
if (this.isShuttingDown) {
|
||||
throw new Error('Service is shutting down');
|
||||
}
|
||||
await this.doWork(job);
|
||||
}
|
||||
}
|
||||
|
||||
// WebSocket gateway cleanup
|
||||
@WebSocketGateway()
|
||||
export class EventsGateway implements OnApplicationShutdown {
|
||||
@WebSocketServer()
|
||||
server: Server;
|
||||
|
||||
async onApplicationShutdown(): Promise<void> {
|
||||
// Notify all connected clients
|
||||
this.server.emit('shutdown', { message: 'Server is shutting down' });
|
||||
|
||||
// Close all connections
|
||||
this.server.disconnectSockets();
|
||||
}
|
||||
}
|
||||
|
||||
// Health check integration
|
||||
@Injectable()
|
||||
export class ShutdownService {
|
||||
private isShuttingDown = false;
|
||||
|
||||
startShutdown(): void {
|
||||
this.isShuttingDown = true;
|
||||
}
|
||||
|
||||
isShutdown(): boolean {
|
||||
return this.isShuttingDown;
|
||||
}
|
||||
}
|
||||
|
||||
@Controller('health')
|
||||
export class HealthController {
|
||||
constructor(private shutdownService: ShutdownService) {}
|
||||
|
||||
@Get('ready')
|
||||
@HealthCheck()
|
||||
readiness(): Promise<HealthCheckResult> {
|
||||
// Return 503 during shutdown - k8s stops sending traffic
|
||||
if (this.shutdownService.isShutdown()) {
|
||||
throw new ServiceUnavailableException('Shutting down');
|
||||
}
|
||||
|
||||
return this.health.check([
|
||||
() => this.db.pingCheck('database'),
|
||||
]);
|
||||
}
|
||||
}
|
||||
|
||||
// Integrate with shutdown
|
||||
@Injectable()
|
||||
export class AppShutdownService implements OnApplicationShutdown {
|
||||
constructor(private shutdownService: ShutdownService) {}
|
||||
|
||||
async onApplicationShutdown(): Promise<void> {
|
||||
// Mark as unhealthy first
|
||||
this.shutdownService.startShutdown();
|
||||
|
||||
// Wait for k8s to update endpoints
|
||||
await this.sleep(5000);
|
||||
|
||||
// Then proceed with cleanup
|
||||
}
|
||||
}
|
||||
|
||||
// Request tracking for in-flight requests
|
||||
@Injectable()
|
||||
export class RequestTracker implements NestMiddleware, OnApplicationShutdown {
|
||||
private activeRequests = 0;
|
||||
private isShuttingDown = false;
|
||||
private shutdownPromise: Promise<void> | null = null;
|
||||
private resolveShutdown: (() => void) | null = null;
|
||||
|
||||
use(req: Request, res: Response, next: NextFunction): void {
|
||||
if (this.isShuttingDown) {
|
||||
res.status(503).send('Service Unavailable');
|
||||
return;
|
||||
}
|
||||
|
||||
this.activeRequests++;
|
||||
|
||||
res.on('finish', () => {
|
||||
this.activeRequests--;
|
||||
if (this.isShuttingDown && this.activeRequests === 0 && this.resolveShutdown) {
|
||||
this.resolveShutdown();
|
||||
}
|
||||
});
|
||||
|
||||
next();
|
||||
}
|
||||
|
||||
async onApplicationShutdown(): Promise<void> {
|
||||
this.isShuttingDown = true;
|
||||
|
||||
if (this.activeRequests > 0) {
|
||||
console.log(`Waiting for ${this.activeRequests} requests to complete`);
|
||||
this.shutdownPromise = new Promise((resolve) => {
|
||||
this.resolveShutdown = resolve;
|
||||
});
|
||||
|
||||
// Wait with timeout
|
||||
await Promise.race([
|
||||
this.shutdownPromise,
|
||||
new Promise((resolve) => setTimeout(resolve, 30000)),
|
||||
]);
|
||||
}
|
||||
|
||||
console.log('All requests completed');
|
||||
}
|
||||
}
|
||||
```
|
||||
|
||||
Reference: [NestJS Lifecycle Events](https://docs.nestjs.com/fundamentals/lifecycle-events)
|
||||
@@ -0,0 +1,167 @@
|
||||
---
|
||||
title: Use ConfigModule for Environment Configuration
|
||||
impact: LOW-MEDIUM
|
||||
impactDescription: Proper configuration prevents deployment failures
|
||||
tags: devops, configuration, environment, validation
|
||||
---
|
||||
|
||||
## Use ConfigModule for Environment Configuration
|
||||
|
||||
Use `@nestjs/config` for environment-based configuration. Validate configuration at startup to fail fast on misconfigurations. Use namespaced configuration for organization and type safety.
|
||||
|
||||
**Incorrect (accessing process.env directly):**
|
||||
|
||||
```typescript
|
||||
// Access process.env directly
|
||||
@Injectable()
|
||||
export class DatabaseService {
|
||||
constructor() {
|
||||
// No validation, can fail at runtime
|
||||
this.connection = new Pool({
|
||||
host: process.env.DB_HOST,
|
||||
port: parseInt(process.env.DB_PORT), // NaN if missing
|
||||
password: process.env.DB_PASSWORD, // undefined if missing
|
||||
});
|
||||
}
|
||||
}
|
||||
|
||||
// Scattered env access
|
||||
@Injectable()
|
||||
export class EmailService {
|
||||
sendEmail() {
|
||||
// Different services access env differently
|
||||
const apiKey = process.env.SENDGRID_API_KEY || 'default';
|
||||
// Typos go unnoticed: process.env.SENDGRID_API_KY
|
||||
}
|
||||
}
|
||||
```
|
||||
|
||||
**Correct (use @nestjs/config with validation):**
|
||||
|
||||
```typescript
|
||||
// Setup validated configuration
|
||||
import { ConfigModule, ConfigService, registerAs } from '@nestjs/config';
|
||||
import * as Joi from 'joi';
|
||||
|
||||
// config/database.config.ts
|
||||
export const databaseConfig = registerAs('database', () => ({
|
||||
host: process.env.DB_HOST,
|
||||
port: parseInt(process.env.DB_PORT, 10),
|
||||
username: process.env.DB_USERNAME,
|
||||
password: process.env.DB_PASSWORD,
|
||||
database: process.env.DB_NAME,
|
||||
}));
|
||||
|
||||
// config/app.config.ts
|
||||
export const appConfig = registerAs('app', () => ({
|
||||
port: parseInt(process.env.PORT, 10) || 3000,
|
||||
environment: process.env.NODE_ENV || 'development',
|
||||
apiPrefix: process.env.API_PREFIX || 'api',
|
||||
}));
|
||||
|
||||
// config/validation.schema.ts
|
||||
export const validationSchema = Joi.object({
|
||||
NODE_ENV: Joi.string()
|
||||
.valid('development', 'production', 'test')
|
||||
.default('development'),
|
||||
PORT: Joi.number().default(3000),
|
||||
DB_HOST: Joi.string().required(),
|
||||
DB_PORT: Joi.number().default(5432),
|
||||
DB_USERNAME: Joi.string().required(),
|
||||
DB_PASSWORD: Joi.string().required(),
|
||||
DB_NAME: Joi.string().required(),
|
||||
JWT_SECRET: Joi.string().min(32).required(),
|
||||
REDIS_URL: Joi.string().uri().required(),
|
||||
});
|
||||
|
||||
// app.module.ts
|
||||
@Module({
|
||||
imports: [
|
||||
ConfigModule.forRoot({
|
||||
isGlobal: true, // Available everywhere without importing
|
||||
load: [databaseConfig, appConfig],
|
||||
validationSchema,
|
||||
validationOptions: {
|
||||
abortEarly: true, // Stop on first error
|
||||
allowUnknown: true, // Allow other env vars
|
||||
},
|
||||
}),
|
||||
TypeOrmModule.forRootAsync({
|
||||
inject: [ConfigService],
|
||||
useFactory: (config: ConfigService) => ({
|
||||
type: 'postgres',
|
||||
host: config.get('database.host'),
|
||||
port: config.get('database.port'),
|
||||
username: config.get('database.username'),
|
||||
password: config.get('database.password'),
|
||||
database: config.get('database.database'),
|
||||
autoLoadEntities: true,
|
||||
}),
|
||||
}),
|
||||
],
|
||||
})
|
||||
export class AppModule {}
|
||||
|
||||
// Type-safe configuration access
|
||||
export interface AppConfig {
|
||||
port: number;
|
||||
environment: 'development' | 'production' | 'test';
|
||||
apiPrefix: string;
|
||||
}
|
||||
|
||||
export interface DatabaseConfig {
|
||||
host: string;
|
||||
port: number;
|
||||
username: string;
|
||||
password: string;
|
||||
database: string;
|
||||
}
|
||||
|
||||
// Type-safe access
|
||||
@Injectable()
|
||||
export class AppService {
|
||||
constructor(private config: ConfigService) {}
|
||||
|
||||
getPort(): number {
|
||||
// Type-safe with generic
|
||||
return this.config.get<number>('app.port');
|
||||
}
|
||||
|
||||
getDatabaseConfig(): DatabaseConfig {
|
||||
return this.config.get<DatabaseConfig>('database');
|
||||
}
|
||||
}
|
||||
|
||||
// Inject namespaced config directly
|
||||
@Injectable()
|
||||
export class DatabaseService {
|
||||
constructor(
|
||||
@Inject(databaseConfig.KEY)
|
||||
private dbConfig: ConfigType<typeof databaseConfig>,
|
||||
) {
|
||||
// Full type inference!
|
||||
const host = this.dbConfig.host; // string
|
||||
const port = this.dbConfig.port; // number
|
||||
}
|
||||
}
|
||||
|
||||
// Environment files support
|
||||
ConfigModule.forRoot({
|
||||
envFilePath: [
|
||||
`.env.${process.env.NODE_ENV}.local`,
|
||||
`.env.${process.env.NODE_ENV}`,
|
||||
'.env.local',
|
||||
'.env',
|
||||
],
|
||||
});
|
||||
|
||||
// .env.development
|
||||
// DB_HOST=localhost
|
||||
// DB_PORT=5432
|
||||
|
||||
// .env.production
|
||||
// DB_HOST=prod-db.example.com
|
||||
// DB_PORT=5432
|
||||
```
|
||||
|
||||
Reference: [NestJS Configuration](https://docs.nestjs.com/techniques/configuration)
|
||||
@@ -0,0 +1,232 @@
|
||||
---
|
||||
title: Use Structured Logging
|
||||
impact: MEDIUM-HIGH
|
||||
impactDescription: Structured logging enables effective debugging and monitoring
|
||||
tags: devops, logging, structured-logs, pino
|
||||
---
|
||||
|
||||
## Use Structured Logging
|
||||
|
||||
Use NestJS Logger with structured JSON output in production. Include contextual information (request ID, user ID, operation) to trace requests across services. Avoid console.log and implement proper log levels.
|
||||
|
||||
**Incorrect (using console.log in production):**
|
||||
|
||||
```typescript
|
||||
// Use console.log in production
|
||||
@Injectable()
|
||||
export class UsersService {
|
||||
async createUser(dto: CreateUserDto): Promise<User> {
|
||||
console.log('Creating user:', dto);
|
||||
// Not structured, no levels, lost in production logs
|
||||
|
||||
try {
|
||||
const user = await this.repo.save(dto);
|
||||
console.log('User created:', user.id);
|
||||
return user;
|
||||
} catch (error) {
|
||||
console.log('Error:', error); // Using log for errors
|
||||
throw error;
|
||||
}
|
||||
}
|
||||
}
|
||||
|
||||
// Log sensitive data
|
||||
console.log('Login attempt:', { email, password }); // SECURITY RISK!
|
||||
|
||||
// Inconsistent log format
|
||||
logger.log('User ' + userId + ' created at ' + new Date());
|
||||
// Hard to parse, no structure
|
||||
```
|
||||
|
||||
**Correct (use structured logging with context):**
|
||||
|
||||
```typescript
|
||||
// Configure logger in main.ts
|
||||
async function bootstrap() {
|
||||
const app = await NestFactory.create(AppModule, {
|
||||
logger:
|
||||
process.env.NODE_ENV === 'production'
|
||||
? ['error', 'warn', 'log']
|
||||
: ['error', 'warn', 'log', 'debug', 'verbose'],
|
||||
});
|
||||
}
|
||||
|
||||
// Use NestJS Logger with context
|
||||
@Injectable()
|
||||
export class UsersService {
|
||||
private readonly logger = new Logger(UsersService.name);
|
||||
|
||||
async createUser(dto: CreateUserDto): Promise<User> {
|
||||
this.logger.log('Creating user', { email: dto.email });
|
||||
|
||||
try {
|
||||
const user = await this.repo.save(dto);
|
||||
this.logger.log('User created', { userId: user.id });
|
||||
return user;
|
||||
} catch (error) {
|
||||
this.logger.error('Failed to create user', error.stack, {
|
||||
email: dto.email,
|
||||
});
|
||||
throw error;
|
||||
}
|
||||
}
|
||||
}
|
||||
|
||||
// Custom logger for JSON output
|
||||
@Injectable()
|
||||
export class JsonLogger implements LoggerService {
|
||||
log(message: string, context?: object): void {
|
||||
console.log(
|
||||
JSON.stringify({
|
||||
level: 'info',
|
||||
timestamp: new Date().toISOString(),
|
||||
message,
|
||||
...context,
|
||||
}),
|
||||
);
|
||||
}
|
||||
|
||||
error(message: string, trace?: string, context?: object): void {
|
||||
console.error(
|
||||
JSON.stringify({
|
||||
level: 'error',
|
||||
timestamp: new Date().toISOString(),
|
||||
message,
|
||||
trace,
|
||||
...context,
|
||||
}),
|
||||
);
|
||||
}
|
||||
|
||||
warn(message: string, context?: object): void {
|
||||
console.warn(
|
||||
JSON.stringify({
|
||||
level: 'warn',
|
||||
timestamp: new Date().toISOString(),
|
||||
message,
|
||||
...context,
|
||||
}),
|
||||
);
|
||||
}
|
||||
|
||||
debug(message: string, context?: object): void {
|
||||
console.debug(
|
||||
JSON.stringify({
|
||||
level: 'debug',
|
||||
timestamp: new Date().toISOString(),
|
||||
message,
|
||||
...context,
|
||||
}),
|
||||
);
|
||||
}
|
||||
}
|
||||
|
||||
// Request context logging with ClsModule
|
||||
import { ClsModule, ClsService } from 'nestjs-cls';
|
||||
|
||||
@Module({
|
||||
imports: [
|
||||
ClsModule.forRoot({
|
||||
global: true,
|
||||
middleware: {
|
||||
mount: true,
|
||||
generateId: true,
|
||||
},
|
||||
}),
|
||||
],
|
||||
})
|
||||
export class AppModule {}
|
||||
|
||||
// Middleware to set request context
|
||||
@Injectable()
|
||||
export class RequestContextMiddleware implements NestMiddleware {
|
||||
constructor(private cls: ClsService) {}
|
||||
|
||||
use(req: Request, res: Response, next: NextFunction): void {
|
||||
const requestId = req.headers['x-request-id'] || randomUUID();
|
||||
this.cls.set('requestId', requestId);
|
||||
this.cls.set('userId', req.user?.id);
|
||||
|
||||
res.setHeader('x-request-id', requestId);
|
||||
next();
|
||||
}
|
||||
}
|
||||
|
||||
// Logger that includes request context
|
||||
@Injectable()
|
||||
export class ContextLogger {
|
||||
constructor(private cls: ClsService) {}
|
||||
|
||||
log(message: string, data?: object): void {
|
||||
console.log(
|
||||
JSON.stringify({
|
||||
level: 'info',
|
||||
timestamp: new Date().toISOString(),
|
||||
requestId: this.cls.get('requestId'),
|
||||
userId: this.cls.get('userId'),
|
||||
message,
|
||||
...data,
|
||||
}),
|
||||
);
|
||||
}
|
||||
|
||||
error(message: string, error: Error, data?: object): void {
|
||||
console.error(
|
||||
JSON.stringify({
|
||||
level: 'error',
|
||||
timestamp: new Date().toISOString(),
|
||||
requestId: this.cls.get('requestId'),
|
||||
userId: this.cls.get('userId'),
|
||||
message,
|
||||
error: error.message,
|
||||
stack: error.stack,
|
||||
...data,
|
||||
}),
|
||||
);
|
||||
}
|
||||
}
|
||||
|
||||
// Pino integration for high-performance logging
|
||||
import { LoggerModule } from 'nestjs-pino';
|
||||
|
||||
@Module({
|
||||
imports: [
|
||||
LoggerModule.forRoot({
|
||||
pinoHttp: {
|
||||
level: process.env.NODE_ENV === 'production' ? 'info' : 'debug',
|
||||
transport:
|
||||
process.env.NODE_ENV !== 'production'
|
||||
? { target: 'pino-pretty' }
|
||||
: undefined,
|
||||
redact: ['req.headers.authorization', 'req.body.password'],
|
||||
serializers: {
|
||||
req: (req) => ({
|
||||
method: req.method,
|
||||
url: req.url,
|
||||
query: req.query,
|
||||
}),
|
||||
res: (res) => ({
|
||||
statusCode: res.statusCode,
|
||||
}),
|
||||
},
|
||||
},
|
||||
}),
|
||||
],
|
||||
})
|
||||
export class AppModule {}
|
||||
|
||||
// Usage with Pino
|
||||
@Injectable()
|
||||
export class UsersService {
|
||||
constructor(private logger: PinoLogger) {
|
||||
this.logger.setContext(UsersService.name);
|
||||
}
|
||||
|
||||
async findOne(id: string): Promise<User> {
|
||||
this.logger.info({ userId: id }, 'Finding user');
|
||||
// Pino uses first arg for data, second for message
|
||||
}
|
||||
}
|
||||
```
|
||||
|
||||
Reference: [NestJS Logger](https://docs.nestjs.com/techniques/logger)
|
||||
@@ -0,0 +1,104 @@
|
||||
---
|
||||
title: Avoid Service Locator Anti-Pattern
|
||||
impact: HIGH
|
||||
impactDescription: Hides dependencies and breaks testability
|
||||
tags: dependency-injection, anti-patterns, testing
|
||||
---
|
||||
|
||||
## Avoid Service Locator Anti-Pattern
|
||||
|
||||
Avoid using `ModuleRef.get()` or global containers to resolve dependencies at runtime. This hides dependencies, makes code harder to test, and breaks the benefits of dependency injection. Use constructor injection instead.
|
||||
|
||||
**Incorrect (service locator anti-pattern):**
|
||||
|
||||
```typescript
|
||||
// Use ModuleRef to get dependencies dynamically
|
||||
@Injectable()
|
||||
export class OrdersService {
|
||||
constructor(private moduleRef: ModuleRef) {}
|
||||
|
||||
async createOrder(dto: CreateOrderDto): Promise<Order> {
|
||||
// Dependencies are hidden - not visible in constructor
|
||||
const usersService = this.moduleRef.get(UsersService);
|
||||
const inventoryService = this.moduleRef.get(InventoryService);
|
||||
const paymentService = this.moduleRef.get(PaymentService);
|
||||
|
||||
const user = await usersService.findOne(dto.userId);
|
||||
// ... rest of logic
|
||||
}
|
||||
}
|
||||
|
||||
// Global singleton container
|
||||
class ServiceContainer {
|
||||
private static instance: ServiceContainer;
|
||||
private services = new Map<string, any>();
|
||||
|
||||
static getInstance(): ServiceContainer {
|
||||
if (!this.instance) {
|
||||
this.instance = new ServiceContainer();
|
||||
}
|
||||
return this.instance;
|
||||
}
|
||||
|
||||
get<T>(key: string): T {
|
||||
return this.services.get(key);
|
||||
}
|
||||
}
|
||||
```
|
||||
|
||||
**Correct (constructor injection with explicit dependencies):**
|
||||
|
||||
```typescript
|
||||
// Use constructor injection - dependencies are explicit
|
||||
@Injectable()
|
||||
export class OrdersService {
|
||||
constructor(
|
||||
private usersService: UsersService,
|
||||
private inventoryService: InventoryService,
|
||||
private paymentService: PaymentService,
|
||||
) {}
|
||||
|
||||
async createOrder(dto: CreateOrderDto): Promise<Order> {
|
||||
const user = await this.usersService.findOne(dto.userId);
|
||||
const inventory = await this.inventoryService.check(dto.items);
|
||||
// Dependencies are clear and testable
|
||||
}
|
||||
}
|
||||
|
||||
// Easy to test with mocks
|
||||
describe('OrdersService', () => {
|
||||
let service: OrdersService;
|
||||
|
||||
beforeEach(async () => {
|
||||
const module = await Test.createTestingModule({
|
||||
providers: [
|
||||
OrdersService,
|
||||
{ provide: UsersService, useValue: mockUsersService },
|
||||
{ provide: InventoryService, useValue: mockInventoryService },
|
||||
{ provide: PaymentService, useValue: mockPaymentService },
|
||||
],
|
||||
}).compile();
|
||||
|
||||
service = module.get(OrdersService);
|
||||
});
|
||||
});
|
||||
|
||||
// VALID: Factory pattern for dynamic instantiation
|
||||
@Injectable()
|
||||
export class HandlerFactory {
|
||||
constructor(private moduleRef: ModuleRef) {}
|
||||
|
||||
getHandler(type: string): Handler {
|
||||
switch (type) {
|
||||
case 'email':
|
||||
return this.moduleRef.get(EmailHandler);
|
||||
case 'sms':
|
||||
return this.moduleRef.get(SmsHandler);
|
||||
default:
|
||||
return this.moduleRef.get(DefaultHandler);
|
||||
}
|
||||
}
|
||||
}
|
||||
```
|
||||
|
||||
Reference: [NestJS Module Reference](https://docs.nestjs.com/fundamentals/module-ref)
|
||||
@@ -0,0 +1,165 @@
|
||||
---
|
||||
title: Apply Interface Segregation Principle
|
||||
impact: HIGH
|
||||
impactDescription: Reduces coupling and improves testability by 30-50%
|
||||
tags: dependency-injection, interfaces, solid, isp
|
||||
---
|
||||
|
||||
## Apply Interface Segregation Principle
|
||||
|
||||
Clients should not be forced to depend on interfaces they don't use. In NestJS, this means keeping interfaces small and focused on specific capabilities rather than creating "fat" interfaces that bundle unrelated methods. When a service only needs to send emails, it shouldn't depend on an interface that also includes SMS, push notifications, and logging. Split large interfaces into role-based ones.
|
||||
|
||||
**Incorrect (fat interface forcing unused dependencies):**
|
||||
|
||||
```typescript
|
||||
// Fat interface - forces all consumers to depend on everything
|
||||
interface NotificationService {
|
||||
sendEmail(to: string, subject: string, body: string): Promise<void>;
|
||||
sendSms(phone: string, message: string): Promise<void>;
|
||||
sendPush(userId: string, notification: PushPayload): Promise<void>;
|
||||
sendSlack(channel: string, message: string): Promise<void>;
|
||||
logNotification(type: string, payload: any): Promise<void>;
|
||||
getDeliveryStatus(id: string): Promise<DeliveryStatus>;
|
||||
retryFailed(id: string): Promise<void>;
|
||||
scheduleNotification(dto: ScheduleDto): Promise<string>;
|
||||
}
|
||||
|
||||
// Consumer only needs email, but must mock everything for tests
|
||||
@Injectable()
|
||||
export class OrdersService {
|
||||
constructor(
|
||||
private notifications: NotificationService, // Depends on 8 methods, uses 1
|
||||
) {}
|
||||
|
||||
async confirmOrder(order: Order): Promise<void> {
|
||||
await this.notifications.sendEmail(
|
||||
order.customer.email,
|
||||
'Order Confirmed',
|
||||
`Your order ${order.id} has been confirmed.`,
|
||||
);
|
||||
}
|
||||
}
|
||||
|
||||
// Testing is painful - must mock unused methods
|
||||
const mockNotificationService = {
|
||||
sendEmail: jest.fn(),
|
||||
sendSms: jest.fn(), // Never used, but required
|
||||
sendPush: jest.fn(), // Never used, but required
|
||||
sendSlack: jest.fn(), // Never used, but required
|
||||
logNotification: jest.fn(), // Never used, but required
|
||||
getDeliveryStatus: jest.fn(), // Never used, but required
|
||||
retryFailed: jest.fn(), // Never used, but required
|
||||
scheduleNotification: jest.fn(), // Never used, but required
|
||||
};
|
||||
```
|
||||
|
||||
**Correct (segregated interfaces by capability):**
|
||||
|
||||
```typescript
|
||||
// Segregated interfaces - each focused on one capability
|
||||
interface EmailSender {
|
||||
sendEmail(to: string, subject: string, body: string): Promise<void>;
|
||||
}
|
||||
|
||||
interface SmsSender {
|
||||
sendSms(phone: string, message: string): Promise<void>;
|
||||
}
|
||||
|
||||
interface PushSender {
|
||||
sendPush(userId: string, notification: PushPayload): Promise<void>;
|
||||
}
|
||||
|
||||
interface NotificationLogger {
|
||||
logNotification(type: string, payload: any): Promise<void>;
|
||||
}
|
||||
|
||||
interface NotificationScheduler {
|
||||
scheduleNotification(dto: ScheduleDto): Promise<string>;
|
||||
}
|
||||
|
||||
// Implementation can implement multiple interfaces
|
||||
@Injectable()
|
||||
export class NotificationService implements EmailSender, SmsSender, PushSender {
|
||||
async sendEmail(to: string, subject: string, body: string): Promise<void> {
|
||||
// Email implementation
|
||||
}
|
||||
|
||||
async sendSms(phone: string, message: string): Promise<void> {
|
||||
// SMS implementation
|
||||
}
|
||||
|
||||
async sendPush(userId: string, notification: PushPayload): Promise<void> {
|
||||
// Push implementation
|
||||
}
|
||||
}
|
||||
|
||||
// Or separate implementations
|
||||
@Injectable()
|
||||
export class SendGridEmailService implements EmailSender {
|
||||
async sendEmail(to: string, subject: string, body: string): Promise<void> {
|
||||
// SendGrid-specific implementation
|
||||
}
|
||||
}
|
||||
|
||||
// Consumer depends only on what it needs
|
||||
@Injectable()
|
||||
export class OrdersService {
|
||||
constructor(
|
||||
@Inject(EMAIL_SENDER) private emailSender: EmailSender, // Minimal dependency
|
||||
) {}
|
||||
|
||||
async confirmOrder(order: Order): Promise<void> {
|
||||
await this.emailSender.sendEmail(
|
||||
order.customer.email,
|
||||
'Order Confirmed',
|
||||
`Your order ${order.id} has been confirmed.`,
|
||||
);
|
||||
}
|
||||
}
|
||||
|
||||
// Testing is simple - only mock what's used
|
||||
const mockEmailSender: EmailSender = {
|
||||
sendEmail: jest.fn(),
|
||||
};
|
||||
|
||||
// Module registration with tokens
|
||||
export const EMAIL_SENDER = Symbol('EMAIL_SENDER');
|
||||
export const SMS_SENDER = Symbol('SMS_SENDER');
|
||||
|
||||
@Module({
|
||||
providers: [
|
||||
{ provide: EMAIL_SENDER, useClass: SendGridEmailService },
|
||||
{ provide: SMS_SENDER, useClass: TwilioSmsService },
|
||||
],
|
||||
exports: [EMAIL_SENDER, SMS_SENDER],
|
||||
})
|
||||
export class NotificationModule {}
|
||||
```
|
||||
|
||||
**Combining interfaces when needed:**
|
||||
|
||||
```typescript
|
||||
// Sometimes a consumer legitimately needs multiple capabilities
|
||||
interface EmailAndSmsSender extends EmailSender, SmsSender {}
|
||||
|
||||
// Or use intersection types
|
||||
type MultiChannelSender = EmailSender & SmsSender & PushSender;
|
||||
|
||||
// Consumer that genuinely needs multiple channels
|
||||
@Injectable()
|
||||
export class AlertService {
|
||||
constructor(
|
||||
@Inject(MULTI_CHANNEL_SENDER)
|
||||
private sender: EmailSender & SmsSender,
|
||||
) {}
|
||||
|
||||
async sendCriticalAlert(user: User, message: string): Promise<void> {
|
||||
await Promise.all([
|
||||
this.sender.sendEmail(user.email, 'Critical Alert', message),
|
||||
this.sender.sendSms(user.phone, message),
|
||||
]);
|
||||
}
|
||||
}
|
||||
```
|
||||
|
||||
Reference: [Interface Segregation Principle](https://en.wikipedia.org/wiki/Interface_segregation_principle)
|
||||
@@ -0,0 +1,221 @@
|
||||
---
|
||||
title: Honor Liskov Substitution Principle
|
||||
impact: HIGH
|
||||
impactDescription: Ensures implementations are truly interchangeable without breaking callers
|
||||
tags: dependency-injection, inheritance, solid, lsp
|
||||
---
|
||||
|
||||
## Honor Liskov Substitution Principle
|
||||
|
||||
Subtypes must be substitutable for their base types without altering program correctness. In NestJS with dependency injection, this means any implementation of an interface or abstract class must honor the contract completely. A mock payment service used in tests must behave like a real payment service (return similar shapes, handle errors the same way). Violating LSP causes subtle bugs when swapping implementations.
|
||||
|
||||
**Incorrect (implementation violates the contract):**
|
||||
|
||||
```typescript
|
||||
// Base interface with clear contract
|
||||
interface PaymentGateway {
|
||||
/**
|
||||
* Charges the specified amount.
|
||||
* @returns PaymentResult on success
|
||||
* @throws PaymentFailedException on payment failure
|
||||
*/
|
||||
charge(amount: number, currency: string): Promise<PaymentResult>;
|
||||
}
|
||||
|
||||
// Production implementation - follows the contract
|
||||
@Injectable()
|
||||
export class StripeService implements PaymentGateway {
|
||||
async charge(amount: number, currency: string): Promise<PaymentResult> {
|
||||
const response = await this.stripe.charges.create({ amount, currency });
|
||||
return { success: true, transactionId: response.id, amount };
|
||||
}
|
||||
}
|
||||
|
||||
// Mock that violates LSP - different behavior!
|
||||
@Injectable()
|
||||
export class MockPaymentService implements PaymentGateway {
|
||||
async charge(amount: number, currency: string): Promise<PaymentResult> {
|
||||
// VIOLATION 1: Throws for valid input (contract says return PaymentResult)
|
||||
if (amount > 1000) {
|
||||
throw new Error('Mock does not support large amounts');
|
||||
}
|
||||
|
||||
// VIOLATION 2: Returns null instead of PaymentResult
|
||||
if (currency !== 'USD') {
|
||||
return null as any; // Real service would convert or reject properly
|
||||
}
|
||||
|
||||
// VIOLATION 3: Missing required field
|
||||
return { success: true } as PaymentResult; // Missing transactionId!
|
||||
}
|
||||
}
|
||||
|
||||
// Consumer trusts the contract
|
||||
@Injectable()
|
||||
export class OrdersService {
|
||||
constructor(@Inject(PAYMENT_GATEWAY) private payment: PaymentGateway) {}
|
||||
|
||||
async checkout(order: Order): Promise<void> {
|
||||
const result = await this.payment.charge(order.total, order.currency);
|
||||
// These fail with MockPaymentService:
|
||||
await this.saveTransaction(result.transactionId); // undefined!
|
||||
await this.sendReceipt(result); // might be null!
|
||||
}
|
||||
}
|
||||
```
|
||||
|
||||
**Correct (implementations honor the contract):**
|
||||
|
||||
```typescript
|
||||
// Well-defined interface with documented behavior
|
||||
interface PaymentGateway {
|
||||
/**
|
||||
* Charges the specified amount.
|
||||
* @param amount - Amount in smallest currency unit (cents)
|
||||
* @param currency - ISO 4217 currency code
|
||||
* @returns PaymentResult with transactionId, success status, and amount
|
||||
* @throws PaymentFailedException if charge is declined
|
||||
* @throws InvalidCurrencyException if currency is not supported
|
||||
*/
|
||||
charge(amount: number, currency: string): Promise<PaymentResult>;
|
||||
|
||||
/**
|
||||
* Refunds a previous charge.
|
||||
* @throws TransactionNotFoundException if transactionId is invalid
|
||||
*/
|
||||
refund(transactionId: string, amount?: number): Promise<RefundResult>;
|
||||
}
|
||||
|
||||
// Production implementation
|
||||
@Injectable()
|
||||
export class StripeService implements PaymentGateway {
|
||||
async charge(amount: number, currency: string): Promise<PaymentResult> {
|
||||
try {
|
||||
const response = await this.stripe.charges.create({ amount, currency });
|
||||
return {
|
||||
success: true,
|
||||
transactionId: response.id,
|
||||
amount: response.amount,
|
||||
};
|
||||
} catch (error) {
|
||||
if (error.type === 'card_error') {
|
||||
throw new PaymentFailedException(error.message);
|
||||
}
|
||||
throw error;
|
||||
}
|
||||
}
|
||||
|
||||
async refund(transactionId: string, amount?: number): Promise<RefundResult> {
|
||||
// Implementation...
|
||||
}
|
||||
}
|
||||
|
||||
// Mock that honors LSP - same contract, same behavior shape
|
||||
@Injectable()
|
||||
export class MockPaymentService implements PaymentGateway {
|
||||
private transactions = new Map<string, PaymentResult>();
|
||||
|
||||
async charge(amount: number, currency: string): Promise<PaymentResult> {
|
||||
// Honor the contract: validate currency like real service would
|
||||
if (!['USD', 'EUR', 'GBP'].includes(currency)) {
|
||||
throw new InvalidCurrencyException(`Unsupported currency: ${currency}`);
|
||||
}
|
||||
|
||||
// Simulate decline for specific test scenarios
|
||||
if (amount === 99999) {
|
||||
throw new PaymentFailedException('Card declined (test scenario)');
|
||||
}
|
||||
|
||||
// Return same shape as production
|
||||
const result: PaymentResult = {
|
||||
success: true,
|
||||
transactionId: `mock_${Date.now()}_${Math.random().toString(36)}`,
|
||||
amount,
|
||||
};
|
||||
|
||||
this.transactions.set(result.transactionId, result);
|
||||
return result;
|
||||
}
|
||||
|
||||
async refund(transactionId: string, amount?: number): Promise<RefundResult> {
|
||||
// Honor the contract: throw if transaction not found
|
||||
if (!this.transactions.has(transactionId)) {
|
||||
throw new TransactionNotFoundException(transactionId);
|
||||
}
|
||||
|
||||
return {
|
||||
success: true,
|
||||
refundId: `refund_${transactionId}`,
|
||||
amount: amount ?? this.transactions.get(transactionId)!.amount,
|
||||
};
|
||||
}
|
||||
}
|
||||
|
||||
// Consumer can swap implementations safely
|
||||
@Injectable()
|
||||
export class OrdersService {
|
||||
constructor(@Inject(PAYMENT_GATEWAY) private payment: PaymentGateway) {}
|
||||
|
||||
async checkout(order: Order): Promise<Order> {
|
||||
try {
|
||||
const result = await this.payment.charge(order.total, order.currency);
|
||||
// Works with both StripeService and MockPaymentService
|
||||
order.transactionId = result.transactionId;
|
||||
order.status = 'paid';
|
||||
return order;
|
||||
} catch (error) {
|
||||
if (error instanceof PaymentFailedException) {
|
||||
order.status = 'payment_failed';
|
||||
return order;
|
||||
}
|
||||
throw error;
|
||||
}
|
||||
}
|
||||
}
|
||||
```
|
||||
|
||||
**Testing LSP compliance:**
|
||||
|
||||
```typescript
|
||||
// Shared test suite that any implementation must pass
|
||||
function testPaymentGatewayContract(
|
||||
createGateway: () => PaymentGateway,
|
||||
) {
|
||||
describe('PaymentGateway contract', () => {
|
||||
let gateway: PaymentGateway;
|
||||
|
||||
beforeEach(() => {
|
||||
gateway = createGateway();
|
||||
});
|
||||
|
||||
it('returns PaymentResult with all required fields', async () => {
|
||||
const result = await gateway.charge(1000, 'USD');
|
||||
expect(result).toHaveProperty('success');
|
||||
expect(result).toHaveProperty('transactionId');
|
||||
expect(result).toHaveProperty('amount');
|
||||
expect(typeof result.transactionId).toBe('string');
|
||||
});
|
||||
|
||||
it('throws InvalidCurrencyException for unsupported currency', async () => {
|
||||
await expect(gateway.charge(1000, 'INVALID'))
|
||||
.rejects.toThrow(InvalidCurrencyException);
|
||||
});
|
||||
|
||||
it('throws TransactionNotFoundException for invalid refund', async () => {
|
||||
await expect(gateway.refund('nonexistent'))
|
||||
.rejects.toThrow(TransactionNotFoundException);
|
||||
});
|
||||
});
|
||||
}
|
||||
|
||||
// Run against all implementations
|
||||
describe('StripeService', () => {
|
||||
testPaymentGatewayContract(() => new StripeService(mockStripeClient));
|
||||
});
|
||||
|
||||
describe('MockPaymentService', () => {
|
||||
testPaymentGatewayContract(() => new MockPaymentService());
|
||||
});
|
||||
```
|
||||
|
||||
Reference: [Liskov Substitution Principle](https://en.wikipedia.org/wiki/Liskov_substitution_principle)
|
||||
@@ -0,0 +1,86 @@
|
||||
---
|
||||
title: Prefer Constructor Injection
|
||||
impact: CRITICAL
|
||||
impactDescription: Required for proper DI and testing
|
||||
tags: dependency-injection, constructor, testing
|
||||
---
|
||||
|
||||
## Prefer Constructor Injection
|
||||
|
||||
Always use constructor injection over property injection. Constructor injection makes dependencies explicit, enables TypeScript type checking, ensures dependencies are available when the class is instantiated, and improves testability. This is required for proper DI, testing, and TypeScript support.
|
||||
|
||||
**Incorrect (property injection with hidden dependencies):**
|
||||
|
||||
```typescript
|
||||
// Property injection - avoid unless necessary
|
||||
@Injectable()
|
||||
export class UsersService {
|
||||
@Inject()
|
||||
private userRepo: UserRepository; // Hidden dependency
|
||||
|
||||
@Inject('CONFIG')
|
||||
private config: ConfigType; // Also hidden
|
||||
|
||||
async findAll() {
|
||||
return this.userRepo.find();
|
||||
}
|
||||
}
|
||||
|
||||
// Problems:
|
||||
// 1. Dependencies not visible in constructor
|
||||
// 2. Service can be instantiated without dependencies in tests
|
||||
// 3. TypeScript can't enforce dependency types at instantiation
|
||||
```
|
||||
|
||||
**Correct (constructor injection with explicit dependencies):**
|
||||
|
||||
```typescript
|
||||
// Constructor injection - explicit and testable
|
||||
@Injectable()
|
||||
export class UsersService {
|
||||
constructor(
|
||||
private readonly userRepo: UserRepository,
|
||||
@Inject('CONFIG') private readonly config: ConfigType,
|
||||
) {}
|
||||
|
||||
async findAll(): Promise<User[]> {
|
||||
return this.userRepo.find();
|
||||
}
|
||||
}
|
||||
|
||||
// Testing is straightforward
|
||||
describe('UsersService', () => {
|
||||
let service: UsersService;
|
||||
let mockRepo: jest.Mocked<UserRepository>;
|
||||
|
||||
beforeEach(() => {
|
||||
mockRepo = {
|
||||
find: jest.fn(),
|
||||
save: jest.fn(),
|
||||
} as any;
|
||||
|
||||
service = new UsersService(mockRepo, { dbUrl: 'test' });
|
||||
});
|
||||
|
||||
it('should find all users', async () => {
|
||||
mockRepo.find.mockResolvedValue([{ id: '1', name: 'Test' }]);
|
||||
const result = await service.findAll();
|
||||
expect(result).toHaveLength(1);
|
||||
});
|
||||
});
|
||||
|
||||
// Only use property injection for optional dependencies
|
||||
@Injectable()
|
||||
export class LoggingService {
|
||||
@Optional()
|
||||
@Inject('ANALYTICS')
|
||||
private analytics?: AnalyticsService;
|
||||
|
||||
log(message: string) {
|
||||
console.log(message);
|
||||
this.analytics?.track('log', message); // Optional enhancement
|
||||
}
|
||||
}
|
||||
```
|
||||
|
||||
Reference: [NestJS Providers](https://docs.nestjs.com/providers)
|
||||
@@ -0,0 +1,94 @@
|
||||
---
|
||||
title: Understand Provider Scopes
|
||||
impact: CRITICAL
|
||||
impactDescription: Prevents data leaks and performance issues
|
||||
tags: dependency-injection, scopes, request-context
|
||||
---
|
||||
|
||||
## Understand Provider Scopes
|
||||
|
||||
NestJS has three provider scopes: DEFAULT (singleton), REQUEST (per-request instance), and TRANSIENT (new instance for each injection). Most providers should be singletons. Request-scoped providers have performance implications as they bubble up through the dependency tree. Understanding scopes prevents memory leaks and incorrect data sharing.
|
||||
|
||||
**Incorrect (wrong scope usage):**
|
||||
|
||||
```typescript
|
||||
// Request-scoped when not needed (performance hit)
|
||||
@Injectable({ scope: Scope.REQUEST })
|
||||
export class UsersService {
|
||||
// This creates a new instance for EVERY request
|
||||
// All dependencies also become request-scoped
|
||||
async findAll() {
|
||||
return this.userRepo.find();
|
||||
}
|
||||
}
|
||||
|
||||
// Singleton with mutable request state
|
||||
@Injectable() // Default: singleton
|
||||
export class RequestContextService {
|
||||
private userId: string; // DANGER: Shared across all requests!
|
||||
|
||||
setUser(userId: string) {
|
||||
this.userId = userId; // Overwrites for all concurrent requests
|
||||
}
|
||||
|
||||
getUser() {
|
||||
return this.userId; // Returns wrong user!
|
||||
}
|
||||
}
|
||||
```
|
||||
|
||||
**Correct (appropriate scope for each use case):**
|
||||
|
||||
```typescript
|
||||
// Singleton for stateless services (default, most common)
|
||||
@Injectable()
|
||||
export class UsersService {
|
||||
constructor(private readonly userRepo: UserRepository) {}
|
||||
|
||||
async findById(id: string): Promise<User> {
|
||||
return this.userRepo.findOne({ where: { id } });
|
||||
}
|
||||
}
|
||||
|
||||
// Request-scoped ONLY when you need request context
|
||||
@Injectable({ scope: Scope.REQUEST })
|
||||
export class RequestContextService {
|
||||
private userId: string;
|
||||
|
||||
setUser(userId: string) {
|
||||
this.userId = userId;
|
||||
}
|
||||
|
||||
getUser(): string {
|
||||
return this.userId;
|
||||
}
|
||||
}
|
||||
|
||||
// Better: Use NestJS built-in request context
|
||||
import { REQUEST } from '@nestjs/core';
|
||||
import { Request } from 'express';
|
||||
|
||||
@Injectable({ scope: Scope.REQUEST })
|
||||
export class AuditService {
|
||||
constructor(@Inject(REQUEST) private request: Request) {}
|
||||
|
||||
log(action: string) {
|
||||
console.log(`User ${this.request.user?.id} performed ${action}`);
|
||||
}
|
||||
}
|
||||
|
||||
// Best: Use ClsModule for async context (no scope bubble-up)
|
||||
import { ClsService } from 'nestjs-cls';
|
||||
|
||||
@Injectable() // Stays singleton!
|
||||
export class AuditService {
|
||||
constructor(private cls: ClsService) {}
|
||||
|
||||
log(action: string) {
|
||||
const userId = this.cls.get('userId');
|
||||
console.log(`User ${userId} performed ${action}`);
|
||||
}
|
||||
}
|
||||
```
|
||||
|
||||
Reference: [NestJS Injection Scopes](https://docs.nestjs.com/fundamentals/injection-scopes)
|
||||
@@ -0,0 +1,101 @@
|
||||
---
|
||||
title: Use Injection Tokens for Interfaces
|
||||
impact: HIGH
|
||||
impactDescription: Enables interface-based DI at runtime
|
||||
tags: dependency-injection, tokens, interfaces
|
||||
---
|
||||
|
||||
## Use Injection Tokens for Interfaces
|
||||
|
||||
TypeScript interfaces are erased at compile time and can't be used as injection tokens. Use string tokens, symbols, or abstract classes when you want to inject implementations of interfaces. This enables swapping implementations for testing or different environments.
|
||||
|
||||
**Incorrect (interface can't be used as token):**
|
||||
|
||||
```typescript
|
||||
// Interface can't be used as injection token
|
||||
interface PaymentGateway {
|
||||
charge(amount: number): Promise<PaymentResult>;
|
||||
}
|
||||
|
||||
@Injectable()
|
||||
export class StripeService implements PaymentGateway {
|
||||
charge(amount: number) { /* ... */ }
|
||||
}
|
||||
|
||||
@Injectable()
|
||||
export class OrdersService {
|
||||
// This WON'T work - PaymentGateway doesn't exist at runtime
|
||||
constructor(private payment: PaymentGateway) {}
|
||||
}
|
||||
```
|
||||
|
||||
**Correct (symbol tokens or abstract classes):**
|
||||
|
||||
```typescript
|
||||
// Option 1: String/Symbol tokens (most flexible)
|
||||
export const PAYMENT_GATEWAY = Symbol('PAYMENT_GATEWAY');
|
||||
|
||||
export interface PaymentGateway {
|
||||
charge(amount: number): Promise<PaymentResult>;
|
||||
}
|
||||
|
||||
@Injectable()
|
||||
export class StripeService implements PaymentGateway {
|
||||
async charge(amount: number): Promise<PaymentResult> {
|
||||
// Stripe implementation
|
||||
}
|
||||
}
|
||||
|
||||
@Injectable()
|
||||
export class MockPaymentService implements PaymentGateway {
|
||||
async charge(amount: number): Promise<PaymentResult> {
|
||||
return { success: true, id: 'mock-id' };
|
||||
}
|
||||
}
|
||||
|
||||
// Module registration
|
||||
@Module({
|
||||
providers: [
|
||||
{
|
||||
provide: PAYMENT_GATEWAY,
|
||||
useClass: process.env.NODE_ENV === 'test'
|
||||
? MockPaymentService
|
||||
: StripeService,
|
||||
},
|
||||
],
|
||||
exports: [PAYMENT_GATEWAY],
|
||||
})
|
||||
export class PaymentModule {}
|
||||
|
||||
// Injection
|
||||
@Injectable()
|
||||
export class OrdersService {
|
||||
constructor(
|
||||
@Inject(PAYMENT_GATEWAY) private payment: PaymentGateway,
|
||||
) {}
|
||||
|
||||
async createOrder(dto: CreateOrderDto) {
|
||||
await this.payment.charge(dto.amount);
|
||||
}
|
||||
}
|
||||
|
||||
// Option 2: Abstract class (carries runtime type info)
|
||||
export abstract class PaymentGateway {
|
||||
abstract charge(amount: number): Promise<PaymentResult>;
|
||||
}
|
||||
|
||||
@Injectable()
|
||||
export class StripeService extends PaymentGateway {
|
||||
async charge(amount: number): Promise<PaymentResult> {
|
||||
// Implementation
|
||||
}
|
||||
}
|
||||
|
||||
// No @Inject needed with abstract class
|
||||
@Injectable()
|
||||
export class OrdersService {
|
||||
constructor(private payment: PaymentGateway) {}
|
||||
}
|
||||
```
|
||||
|
||||
Reference: [NestJS Custom Providers](https://docs.nestjs.com/fundamentals/custom-providers)
|
||||
@@ -0,0 +1,125 @@
|
||||
---
|
||||
title: Handle Async Errors Properly
|
||||
impact: HIGH
|
||||
impactDescription: Prevents process crashes from unhandled rejections
|
||||
tags: error-handling, async, promises
|
||||
---
|
||||
|
||||
## Handle Async Errors Properly
|
||||
|
||||
NestJS automatically catches errors from async route handlers, but errors from background tasks, event handlers, and manually created promises can crash your application. Always handle async errors explicitly and use global handlers as a safety net.
|
||||
|
||||
**Incorrect (fire-and-forget without error handling):**
|
||||
|
||||
```typescript
|
||||
// Fire-and-forget without error handling
|
||||
@Injectable()
|
||||
export class UsersService {
|
||||
async createUser(dto: CreateUserDto): Promise<User> {
|
||||
const user = await this.repo.save(dto);
|
||||
|
||||
// Fire and forget - if this fails, error is unhandled!
|
||||
this.emailService.sendWelcome(user.email);
|
||||
|
||||
return user;
|
||||
}
|
||||
}
|
||||
|
||||
// Unhandled promise in event handler
|
||||
@Injectable()
|
||||
export class OrdersService {
|
||||
@OnEvent('order.created')
|
||||
handleOrderCreated(event: OrderCreatedEvent) {
|
||||
// This returns a promise but it's not awaited!
|
||||
this.processOrder(event);
|
||||
// Errors will crash the process
|
||||
}
|
||||
|
||||
private async processOrder(event: OrderCreatedEvent): Promise<void> {
|
||||
await this.inventoryService.reserve(event.items);
|
||||
await this.notificationService.send(event.userId);
|
||||
}
|
||||
}
|
||||
|
||||
// Missing try-catch in scheduled tasks
|
||||
@Cron('0 0 * * *')
|
||||
async dailyCleanup(): Promise<void> {
|
||||
await this.cleanupService.run();
|
||||
// If this throws, no error handling
|
||||
}
|
||||
```
|
||||
|
||||
**Correct (explicit async error handling):**
|
||||
|
||||
```typescript
|
||||
// Handle fire-and-forget with explicit catch
|
||||
@Injectable()
|
||||
export class UsersService {
|
||||
private readonly logger = new Logger(UsersService.name);
|
||||
|
||||
async createUser(dto: CreateUserDto): Promise<User> {
|
||||
const user = await this.repo.save(dto);
|
||||
|
||||
// Explicitly catch and log errors
|
||||
this.emailService.sendWelcome(user.email).catch((error) => {
|
||||
this.logger.error('Failed to send welcome email', error.stack);
|
||||
// Optionally queue for retry
|
||||
});
|
||||
|
||||
return user;
|
||||
}
|
||||
}
|
||||
|
||||
// Properly handle async event handlers
|
||||
@Injectable()
|
||||
export class OrdersService {
|
||||
private readonly logger = new Logger(OrdersService.name);
|
||||
|
||||
@OnEvent('order.created')
|
||||
async handleOrderCreated(event: OrderCreatedEvent): Promise<void> {
|
||||
try {
|
||||
await this.processOrder(event);
|
||||
} catch (error) {
|
||||
this.logger.error('Failed to process order', { event, error });
|
||||
// Don't rethrow - would crash the process
|
||||
await this.deadLetterQueue.add('order.created', event);
|
||||
}
|
||||
}
|
||||
}
|
||||
|
||||
// Safe scheduled tasks
|
||||
@Injectable()
|
||||
export class CleanupService {
|
||||
private readonly logger = new Logger(CleanupService.name);
|
||||
|
||||
@Cron('0 0 * * *')
|
||||
async dailyCleanup(): Promise<void> {
|
||||
try {
|
||||
await this.cleanupService.run();
|
||||
this.logger.log('Daily cleanup completed');
|
||||
} catch (error) {
|
||||
this.logger.error('Daily cleanup failed', error.stack);
|
||||
// Alert or retry logic
|
||||
}
|
||||
}
|
||||
}
|
||||
|
||||
// Global unhandled rejection handler in main.ts
|
||||
async function bootstrap() {
|
||||
const app = await NestFactory.create(AppModule);
|
||||
const logger = new Logger('Bootstrap');
|
||||
|
||||
process.on('unhandledRejection', (reason, promise) => {
|
||||
logger.error('Unhandled Rejection at:', promise, 'reason:', reason);
|
||||
});
|
||||
|
||||
process.on('uncaughtException', (error) => {
|
||||
logger.error('Uncaught Exception:', error);
|
||||
process.exit(1);
|
||||
});
|
||||
|
||||
await app.listen(3000);
|
||||
}
|
||||
```
|
||||
|
||||
Reference: [Node.js Unhandled Rejections](https://nodejs.org/api/process.html#event-unhandledrejection)
|
||||
@@ -0,0 +1,114 @@
|
||||
---
|
||||
title: Throw HTTP Exceptions from Services
|
||||
impact: HIGH
|
||||
impactDescription: Keeps controllers thin and simplifies error handling
|
||||
tags: error-handling, exceptions, services
|
||||
---
|
||||
|
||||
## Throw HTTP Exceptions from Services
|
||||
|
||||
It's acceptable (and often preferable) to throw `HttpException` subclasses from services in HTTP applications. This keeps controllers thin and allows services to communicate appropriate error states. For truly layer-agnostic services, use domain exceptions that map to HTTP status codes.
|
||||
|
||||
**Incorrect (return error objects instead of throwing):**
|
||||
|
||||
```typescript
|
||||
// Return error objects instead of throwing
|
||||
@Injectable()
|
||||
export class UsersService {
|
||||
async findById(id: string): Promise<{ user?: User; error?: string }> {
|
||||
const user = await this.repo.findOne({ where: { id } });
|
||||
if (!user) {
|
||||
return { error: 'User not found' }; // Controller must check this
|
||||
}
|
||||
return { user };
|
||||
}
|
||||
}
|
||||
|
||||
@Controller('users')
|
||||
export class UsersController {
|
||||
@Get(':id')
|
||||
async findOne(@Param('id') id: string) {
|
||||
const result = await this.usersService.findById(id);
|
||||
if (result.error) {
|
||||
throw new NotFoundException(result.error);
|
||||
}
|
||||
return result.user;
|
||||
}
|
||||
}
|
||||
```
|
||||
|
||||
**Correct (throw exceptions directly from service):**
|
||||
|
||||
```typescript
|
||||
// Throw exceptions directly from service
|
||||
@Injectable()
|
||||
export class UsersService {
|
||||
constructor(private readonly repo: UserRepository) {}
|
||||
|
||||
async findById(id: string): Promise<User> {
|
||||
const user = await this.repo.findOne({ where: { id } });
|
||||
if (!user) {
|
||||
throw new NotFoundException(`User #${id} not found`);
|
||||
}
|
||||
return user;
|
||||
}
|
||||
|
||||
async create(dto: CreateUserDto): Promise<User> {
|
||||
const existing = await this.repo.findOne({
|
||||
where: { email: dto.email },
|
||||
});
|
||||
if (existing) {
|
||||
throw new ConflictException('Email already registered');
|
||||
}
|
||||
return this.repo.save(dto);
|
||||
}
|
||||
|
||||
async update(id: string, dto: UpdateUserDto): Promise<User> {
|
||||
const user = await this.findById(id); // Throws if not found
|
||||
Object.assign(user, dto);
|
||||
return this.repo.save(user);
|
||||
}
|
||||
}
|
||||
|
||||
// Controller stays thin
|
||||
@Controller('users')
|
||||
export class UsersController {
|
||||
@Get(':id')
|
||||
findOne(@Param('id') id: string): Promise<User> {
|
||||
return this.usersService.findById(id);
|
||||
}
|
||||
|
||||
@Post()
|
||||
create(@Body() dto: CreateUserDto): Promise<User> {
|
||||
return this.usersService.create(dto);
|
||||
}
|
||||
}
|
||||
|
||||
// For layer-agnostic services, use domain exceptions
|
||||
export class EntityNotFoundException extends Error {
|
||||
constructor(
|
||||
public readonly entity: string,
|
||||
public readonly id: string,
|
||||
) {
|
||||
super(`${entity} with ID "${id}" not found`);
|
||||
}
|
||||
}
|
||||
|
||||
// Map to HTTP in exception filter
|
||||
@Catch(EntityNotFoundException)
|
||||
export class EntityNotFoundFilter implements ExceptionFilter {
|
||||
catch(exception: EntityNotFoundException, host: ArgumentsHost) {
|
||||
const ctx = host.switchToHttp();
|
||||
const response = ctx.getResponse<Response>();
|
||||
|
||||
response.status(404).json({
|
||||
statusCode: 404,
|
||||
message: exception.message,
|
||||
entity: exception.entity,
|
||||
id: exception.id,
|
||||
});
|
||||
}
|
||||
}
|
||||
```
|
||||
|
||||
Reference: [NestJS Exception Filters](https://docs.nestjs.com/exception-filters)
|
||||
@@ -0,0 +1,140 @@
|
||||
---
|
||||
title: Use Exception Filters for Error Handling
|
||||
impact: HIGH
|
||||
impactDescription: Consistent, centralized error handling
|
||||
tags: error-handling, exception-filters, consistency
|
||||
---
|
||||
|
||||
## Use Exception Filters for Error Handling
|
||||
|
||||
Never catch exceptions and manually format error responses in controllers. Use NestJS exception filters to handle errors consistently across your application. Create custom exception filters for specific error types and a global filter for unhandled exceptions.
|
||||
|
||||
**Incorrect (manual error handling in controllers):**
|
||||
|
||||
```typescript
|
||||
// Manual error handling in controllers
|
||||
@Controller('users')
|
||||
export class UsersController {
|
||||
@Get(':id')
|
||||
async findOne(@Param('id') id: string, @Res() res: Response) {
|
||||
try {
|
||||
const user = await this.usersService.findById(id);
|
||||
if (!user) {
|
||||
return res.status(404).json({
|
||||
statusCode: 404,
|
||||
message: 'User not found',
|
||||
});
|
||||
}
|
||||
return res.json(user);
|
||||
} catch (error) {
|
||||
console.error(error);
|
||||
return res.status(500).json({
|
||||
statusCode: 500,
|
||||
message: 'Internal server error',
|
||||
});
|
||||
}
|
||||
}
|
||||
}
|
||||
```
|
||||
|
||||
**Correct (exception filters with consistent handling):**
|
||||
|
||||
```typescript
|
||||
// Use built-in and custom exceptions
|
||||
@Controller('users')
|
||||
export class UsersController {
|
||||
@Get(':id')
|
||||
async findOne(@Param('id') id: string): Promise<User> {
|
||||
const user = await this.usersService.findById(id);
|
||||
if (!user) {
|
||||
throw new NotFoundException(`User #${id} not found`);
|
||||
}
|
||||
return user;
|
||||
}
|
||||
}
|
||||
|
||||
// Custom domain exception
|
||||
export class UserNotFoundException extends NotFoundException {
|
||||
constructor(userId: string) {
|
||||
super({
|
||||
statusCode: 404,
|
||||
error: 'Not Found',
|
||||
message: `User with ID "${userId}" not found`,
|
||||
code: 'USER_NOT_FOUND',
|
||||
});
|
||||
}
|
||||
}
|
||||
|
||||
// Custom exception filter for domain errors
|
||||
@Catch(DomainException)
|
||||
export class DomainExceptionFilter implements ExceptionFilter {
|
||||
catch(exception: DomainException, host: ArgumentsHost) {
|
||||
const ctx = host.switchToHttp();
|
||||
const response = ctx.getResponse<Response>();
|
||||
const request = ctx.getRequest<Request>();
|
||||
|
||||
const status = exception.getStatus?.() || 400;
|
||||
|
||||
response.status(status).json({
|
||||
statusCode: status,
|
||||
code: exception.code,
|
||||
message: exception.message,
|
||||
timestamp: new Date().toISOString(),
|
||||
path: request.url,
|
||||
});
|
||||
}
|
||||
}
|
||||
|
||||
// Global exception filter for unhandled errors
|
||||
@Catch()
|
||||
export class AllExceptionsFilter implements ExceptionFilter {
|
||||
constructor(private readonly logger: Logger) {}
|
||||
|
||||
catch(exception: unknown, host: ArgumentsHost) {
|
||||
const ctx = host.switchToHttp();
|
||||
const response = ctx.getResponse<Response>();
|
||||
const request = ctx.getRequest<Request>();
|
||||
|
||||
const status =
|
||||
exception instanceof HttpException
|
||||
? exception.getStatus()
|
||||
: HttpStatus.INTERNAL_SERVER_ERROR;
|
||||
|
||||
const message =
|
||||
exception instanceof HttpException
|
||||
? exception.message
|
||||
: 'Internal server error';
|
||||
|
||||
this.logger.error(
|
||||
`${request.method} ${request.url}`,
|
||||
exception instanceof Error ? exception.stack : exception,
|
||||
);
|
||||
|
||||
response.status(status).json({
|
||||
statusCode: status,
|
||||
message,
|
||||
timestamp: new Date().toISOString(),
|
||||
path: request.url,
|
||||
});
|
||||
}
|
||||
}
|
||||
|
||||
// Register globally in main.ts
|
||||
app.useGlobalFilters(
|
||||
new AllExceptionsFilter(app.get(Logger)),
|
||||
new DomainExceptionFilter(),
|
||||
);
|
||||
|
||||
// Or via module
|
||||
@Module({
|
||||
providers: [
|
||||
{
|
||||
provide: APP_FILTER,
|
||||
useClass: AllExceptionsFilter,
|
||||
},
|
||||
],
|
||||
})
|
||||
export class AppModule {}
|
||||
```
|
||||
|
||||
Reference: [NestJS Exception Filters](https://docs.nestjs.com/exception-filters)
|
||||
@@ -0,0 +1,226 @@
|
||||
---
|
||||
title: Implement Health Checks for Microservices
|
||||
impact: MEDIUM-HIGH
|
||||
impactDescription: Health checks enable orchestrators to manage service lifecycle
|
||||
tags: microservices, health-checks, terminus, kubernetes
|
||||
---
|
||||
|
||||
## Implement Health Checks for Microservices
|
||||
|
||||
Implement liveness and readiness probes using `@nestjs/terminus`. Liveness checks determine if the service should be restarted. Readiness checks determine if the service can accept traffic. Proper health checks enable Kubernetes and load balancers to route traffic correctly.
|
||||
|
||||
**Incorrect (simple ping that doesn't check dependencies):**
|
||||
|
||||
```typescript
|
||||
// Simple ping that doesn't check dependencies
|
||||
@Controller('health')
|
||||
export class HealthController {
|
||||
@Get()
|
||||
check(): string {
|
||||
return 'OK'; // Service might be unhealthy but returns OK
|
||||
}
|
||||
}
|
||||
|
||||
// Health check that blocks on slow dependencies
|
||||
@Controller('health')
|
||||
export class HealthController {
|
||||
@Get()
|
||||
async check(): Promise<string> {
|
||||
// If database is slow, health check times out
|
||||
await this.userRepo.findOne({ where: { id: '1' } });
|
||||
await this.redis.ping();
|
||||
await this.externalApi.healthCheck();
|
||||
return 'OK';
|
||||
}
|
||||
}
|
||||
```
|
||||
|
||||
**Correct (use @nestjs/terminus for comprehensive health checks):**
|
||||
|
||||
```typescript
|
||||
// Use @nestjs/terminus for comprehensive health checks
|
||||
import {
|
||||
HealthCheckService,
|
||||
HttpHealthIndicator,
|
||||
TypeOrmHealthIndicator,
|
||||
HealthCheck,
|
||||
DiskHealthIndicator,
|
||||
MemoryHealthIndicator,
|
||||
} from '@nestjs/terminus';
|
||||
|
||||
@Controller('health')
|
||||
export class HealthController {
|
||||
constructor(
|
||||
private health: HealthCheckService,
|
||||
private http: HttpHealthIndicator,
|
||||
private db: TypeOrmHealthIndicator,
|
||||
private disk: DiskHealthIndicator,
|
||||
private memory: MemoryHealthIndicator,
|
||||
) {}
|
||||
|
||||
// Liveness probe - is the service alive?
|
||||
@Get('live')
|
||||
@HealthCheck()
|
||||
liveness() {
|
||||
return this.health.check([
|
||||
// Basic checks only
|
||||
() => this.memory.checkHeap('memory_heap', 200 * 1024 * 1024), // 200MB
|
||||
]);
|
||||
}
|
||||
|
||||
// Readiness probe - can the service handle traffic?
|
||||
@Get('ready')
|
||||
@HealthCheck()
|
||||
readiness() {
|
||||
return this.health.check([
|
||||
() => this.db.pingCheck('database'),
|
||||
() =>
|
||||
this.http.pingCheck('redis', 'http://redis:6379', { timeout: 1000 }),
|
||||
() =>
|
||||
this.disk.checkStorage('disk', { path: '/', thresholdPercent: 0.9 }),
|
||||
]);
|
||||
}
|
||||
|
||||
// Deep health check for debugging
|
||||
@Get('deep')
|
||||
@HealthCheck()
|
||||
deepCheck() {
|
||||
return this.health.check([
|
||||
() => this.db.pingCheck('database'),
|
||||
() => this.memory.checkHeap('memory_heap', 200 * 1024 * 1024),
|
||||
() => this.memory.checkRSS('memory_rss', 300 * 1024 * 1024),
|
||||
() =>
|
||||
this.disk.checkStorage('disk', { path: '/', thresholdPercent: 0.9 }),
|
||||
() =>
|
||||
this.http.pingCheck('external-api', 'https://api.example.com/health'),
|
||||
]);
|
||||
}
|
||||
}
|
||||
|
||||
// Custom indicator for business-specific health
|
||||
@Injectable()
|
||||
export class QueueHealthIndicator extends HealthIndicator {
|
||||
constructor(private queueService: QueueService) {
|
||||
super();
|
||||
}
|
||||
|
||||
async isHealthy(key: string): Promise<HealthIndicatorResult> {
|
||||
const queueStats = await this.queueService.getStats();
|
||||
|
||||
const isHealthy = queueStats.failedCount < 100;
|
||||
const result = this.getStatus(key, isHealthy, {
|
||||
waiting: queueStats.waitingCount,
|
||||
active: queueStats.activeCount,
|
||||
failed: queueStats.failedCount,
|
||||
});
|
||||
|
||||
if (!isHealthy) {
|
||||
throw new HealthCheckError('Queue unhealthy', result);
|
||||
}
|
||||
|
||||
return result;
|
||||
}
|
||||
}
|
||||
|
||||
// Redis health indicator
|
||||
@Injectable()
|
||||
export class RedisHealthIndicator extends HealthIndicator {
|
||||
constructor(@InjectRedis() private redis: Redis) {
|
||||
super();
|
||||
}
|
||||
|
||||
async isHealthy(key: string): Promise<HealthIndicatorResult> {
|
||||
try {
|
||||
const pong = await this.redis.ping();
|
||||
return this.getStatus(key, pong === 'PONG');
|
||||
} catch (error) {
|
||||
throw new HealthCheckError('Redis check failed', this.getStatus(key, false));
|
||||
}
|
||||
}
|
||||
}
|
||||
|
||||
// Use custom indicators
|
||||
@Get('ready')
|
||||
@HealthCheck()
|
||||
readiness() {
|
||||
return this.health.check([
|
||||
() => this.db.pingCheck('database'),
|
||||
() => this.redis.isHealthy('redis'),
|
||||
() => this.queue.isHealthy('job-queue'),
|
||||
]);
|
||||
}
|
||||
|
||||
// Graceful shutdown handling
|
||||
@Injectable()
|
||||
export class GracefulShutdownService implements OnApplicationShutdown {
|
||||
private isShuttingDown = false;
|
||||
|
||||
isShutdown(): boolean {
|
||||
return this.isShuttingDown;
|
||||
}
|
||||
|
||||
async onApplicationShutdown(signal: string): Promise<void> {
|
||||
this.isShuttingDown = true;
|
||||
console.log(`Shutting down on ${signal}`);
|
||||
|
||||
// Wait for in-flight requests
|
||||
await new Promise((resolve) => setTimeout(resolve, 5000));
|
||||
}
|
||||
}
|
||||
|
||||
// Health check respects shutdown state
|
||||
@Get('ready')
|
||||
@HealthCheck()
|
||||
readiness() {
|
||||
if (this.shutdownService.isShutdown()) {
|
||||
throw new ServiceUnavailableException('Shutting down');
|
||||
}
|
||||
|
||||
return this.health.check([
|
||||
() => this.db.pingCheck('database'),
|
||||
]);
|
||||
}
|
||||
```
|
||||
|
||||
### Kubernetes Configuration
|
||||
|
||||
```yaml
|
||||
# Kubernetes deployment with probes
|
||||
apiVersion: apps/v1
|
||||
kind: Deployment
|
||||
metadata:
|
||||
name: api-service
|
||||
spec:
|
||||
template:
|
||||
spec:
|
||||
containers:
|
||||
- name: api
|
||||
image: api-service:latest
|
||||
ports:
|
||||
- containerPort: 3000
|
||||
livenessProbe:
|
||||
httpGet:
|
||||
path: /health/live
|
||||
port: 3000
|
||||
initialDelaySeconds: 30
|
||||
periodSeconds: 10
|
||||
timeoutSeconds: 5
|
||||
failureThreshold: 3
|
||||
readinessProbe:
|
||||
httpGet:
|
||||
path: /health/ready
|
||||
port: 3000
|
||||
initialDelaySeconds: 5
|
||||
periodSeconds: 5
|
||||
timeoutSeconds: 3
|
||||
failureThreshold: 3
|
||||
startupProbe:
|
||||
httpGet:
|
||||
path: /health/live
|
||||
port: 3000
|
||||
initialDelaySeconds: 0
|
||||
periodSeconds: 5
|
||||
failureThreshold: 30
|
||||
```
|
||||
|
||||
Reference: [NestJS Terminus](https://docs.nestjs.com/recipes/terminus)
|
||||
@@ -0,0 +1,167 @@
|
||||
---
|
||||
title: Use Message and Event Patterns Correctly
|
||||
impact: MEDIUM
|
||||
impactDescription: Proper patterns ensure reliable microservice communication
|
||||
tags: microservices, message-pattern, event-pattern, communication
|
||||
---
|
||||
|
||||
## Use Message and Event Patterns Correctly
|
||||
|
||||
NestJS microservices support two communication patterns: request-response (MessagePattern) and event-based (EventPattern). Use MessagePattern when you need a response, and EventPattern for fire-and-forget notifications. Understanding the difference prevents communication bugs.
|
||||
|
||||
**Incorrect (using wrong pattern for use case):**
|
||||
|
||||
```typescript
|
||||
// Use @MessagePattern for fire-and-forget
|
||||
@Controller()
|
||||
export class NotificationsController {
|
||||
@MessagePattern('user.created')
|
||||
async handleUserCreated(data: UserCreatedEvent) {
|
||||
// This WAITS for response, blocking the sender
|
||||
await this.emailService.sendWelcome(data.email);
|
||||
// If email fails, sender gets an error (coupling!)
|
||||
}
|
||||
}
|
||||
|
||||
// Use @EventPattern expecting a response
|
||||
@Controller()
|
||||
export class OrdersController {
|
||||
@EventPattern('inventory.check')
|
||||
async checkInventory(data: CheckInventoryDto) {
|
||||
const available = await this.inventory.check(data);
|
||||
return available; // This return value is IGNORED with @EventPattern!
|
||||
}
|
||||
}
|
||||
|
||||
// Tight coupling in client
|
||||
@Injectable()
|
||||
export class UsersService {
|
||||
async createUser(dto: CreateUserDto): Promise<User> {
|
||||
const user = await this.repo.save(dto);
|
||||
|
||||
// Blocks until notification service responds
|
||||
await this.client.send('user.created', user).toPromise();
|
||||
// If notification service is down, user creation fails!
|
||||
|
||||
return user;
|
||||
}
|
||||
}
|
||||
```
|
||||
|
||||
**Correct (use MessagePattern for request-response, EventPattern for fire-and-forget):**
|
||||
|
||||
```typescript
|
||||
// MessagePattern: Request-Response (when you NEED a response)
|
||||
@Controller()
|
||||
export class InventoryController {
|
||||
@MessagePattern({ cmd: 'check_inventory' })
|
||||
async checkInventory(data: CheckInventoryDto): Promise<InventoryResult> {
|
||||
const result = await this.inventoryService.check(data.productId, data.quantity);
|
||||
return result; // Response sent back to caller
|
||||
}
|
||||
}
|
||||
|
||||
// Client expects response
|
||||
@Injectable()
|
||||
export class OrdersService {
|
||||
async createOrder(dto: CreateOrderDto): Promise<Order> {
|
||||
// Check inventory - we NEED this response to proceed
|
||||
const inventory = await firstValueFrom(
|
||||
this.inventoryClient.send<InventoryResult>(
|
||||
{ cmd: 'check_inventory' },
|
||||
{ productId: dto.productId, quantity: dto.quantity },
|
||||
),
|
||||
);
|
||||
|
||||
if (!inventory.available) {
|
||||
throw new BadRequestException('Insufficient inventory');
|
||||
}
|
||||
|
||||
return this.repo.save(dto);
|
||||
}
|
||||
}
|
||||
|
||||
// EventPattern: Fire-and-Forget (for notifications, side effects)
|
||||
@Controller()
|
||||
export class NotificationsController {
|
||||
@EventPattern('user.created')
|
||||
async handleUserCreated(data: UserCreatedEvent): Promise<void> {
|
||||
// No return value needed - just process the event
|
||||
await this.emailService.sendWelcome(data.email);
|
||||
await this.analyticsService.track('user_signup', data);
|
||||
// If this fails, it doesn't affect the sender
|
||||
}
|
||||
}
|
||||
|
||||
// Client emits event without waiting
|
||||
@Injectable()
|
||||
export class UsersService {
|
||||
async createUser(dto: CreateUserDto): Promise<User> {
|
||||
const user = await this.repo.save(dto);
|
||||
|
||||
// Fire and forget - doesn't block, doesn't wait
|
||||
this.eventClient.emit('user.created', {
|
||||
userId: user.id,
|
||||
email: user.email,
|
||||
timestamp: new Date(),
|
||||
});
|
||||
|
||||
return user; // User creation succeeds regardless of event handling
|
||||
}
|
||||
}
|
||||
|
||||
// Hybrid pattern for critical events
|
||||
@Injectable()
|
||||
export class OrdersService {
|
||||
async createOrder(dto: CreateOrderDto): Promise<Order> {
|
||||
const order = await this.repo.save(dto);
|
||||
|
||||
// Critical: inventory reservation (use MessagePattern)
|
||||
const reserved = await firstValueFrom(
|
||||
this.inventoryClient.send({ cmd: 'reserve_inventory' }, {
|
||||
orderId: order.id,
|
||||
items: dto.items,
|
||||
}),
|
||||
);
|
||||
|
||||
if (!reserved.success) {
|
||||
await this.repo.delete(order.id);
|
||||
throw new BadRequestException('Could not reserve inventory');
|
||||
}
|
||||
|
||||
// Non-critical: notifications (use EventPattern)
|
||||
this.eventClient.emit('order.created', {
|
||||
orderId: order.id,
|
||||
userId: dto.userId,
|
||||
total: dto.total,
|
||||
});
|
||||
|
||||
return order;
|
||||
}
|
||||
}
|
||||
|
||||
// Error handling patterns
|
||||
// MessagePattern errors propagate to caller
|
||||
@MessagePattern({ cmd: 'get_user' })
|
||||
async getUser(userId: string): Promise<User> {
|
||||
const user = await this.repo.findOne({ where: { id: userId } });
|
||||
if (!user) {
|
||||
throw new RpcException('User not found'); // Received by caller
|
||||
}
|
||||
return user;
|
||||
}
|
||||
|
||||
// EventPattern errors should be handled locally
|
||||
@EventPattern('order.created')
|
||||
async handleOrderCreated(data: OrderCreatedEvent): Promise<void> {
|
||||
try {
|
||||
await this.processOrder(data);
|
||||
} catch (error) {
|
||||
// Log and potentially retry - don't throw
|
||||
this.logger.error('Failed to process order event', error);
|
||||
await this.deadLetterQueue.add(data);
|
||||
}
|
||||
}
|
||||
```
|
||||
|
||||
Reference: [NestJS Microservices](https://docs.nestjs.com/microservices/basics)
|
||||
@@ -0,0 +1,252 @@
|
||||
---
|
||||
title: Use Message Queues for Background Jobs
|
||||
impact: MEDIUM-HIGH
|
||||
impactDescription: Queues enable reliable background processing
|
||||
tags: microservices, queues, bullmq, background-jobs
|
||||
---
|
||||
|
||||
## Use Message Queues for Background Jobs
|
||||
|
||||
Use `@nestjs/bullmq` for background job processing. Queues decouple long-running tasks from HTTP requests, enable retry logic, and distribute workload across workers. Use them for emails, file processing, notifications, and any task that shouldn't block user requests.
|
||||
|
||||
**Incorrect (long-running tasks in HTTP handlers):**
|
||||
|
||||
```typescript
|
||||
// Long-running tasks in HTTP handlers
|
||||
@Controller('reports')
|
||||
export class ReportsController {
|
||||
@Post()
|
||||
async generate(@Body() dto: GenerateReportDto): Promise<Report> {
|
||||
// This blocks the request for potentially minutes
|
||||
const data = await this.fetchLargeDataset(dto);
|
||||
const report = await this.processData(data); // Slow!
|
||||
await this.sendEmail(dto.email, report); // Can fail!
|
||||
return report; // Client times out
|
||||
}
|
||||
}
|
||||
|
||||
// Fire-and-forget without retry
|
||||
@Injectable()
|
||||
export class EmailService {
|
||||
async sendWelcome(email: string): Promise<void> {
|
||||
// If this fails, email is never sent
|
||||
await this.mailer.send({ to: email, template: 'welcome' });
|
||||
// No retry, no tracking, no visibility
|
||||
}
|
||||
}
|
||||
|
||||
// Use setInterval for scheduled tasks
|
||||
setInterval(async () => {
|
||||
await cleanupOldRecords();
|
||||
}, 60000); // No error handling, memory leaks
|
||||
```
|
||||
|
||||
**Correct (use BullMQ for background processing):**
|
||||
|
||||
```typescript
|
||||
// Configure BullMQ
|
||||
import { BullModule } from '@nestjs/bullmq';
|
||||
|
||||
@Module({
|
||||
imports: [
|
||||
BullModule.forRoot({
|
||||
connection: {
|
||||
host: 'localhost',
|
||||
port: 6379,
|
||||
},
|
||||
defaultJobOptions: {
|
||||
removeOnComplete: 1000,
|
||||
removeOnFail: 5000,
|
||||
attempts: 3,
|
||||
backoff: {
|
||||
type: 'exponential',
|
||||
delay: 1000,
|
||||
},
|
||||
},
|
||||
}),
|
||||
BullModule.registerQueue(
|
||||
{ name: 'email' },
|
||||
{ name: 'reports' },
|
||||
{ name: 'notifications' },
|
||||
),
|
||||
],
|
||||
})
|
||||
export class QueueModule {}
|
||||
|
||||
// Producer: Add jobs to queue
|
||||
@Injectable()
|
||||
export class ReportsService {
|
||||
constructor(
|
||||
@InjectQueue('reports') private reportsQueue: Queue,
|
||||
) {}
|
||||
|
||||
async requestReport(dto: GenerateReportDto): Promise<{ jobId: string }> {
|
||||
// Return immediately, process in background
|
||||
const job = await this.reportsQueue.add('generate', dto, {
|
||||
priority: dto.urgent ? 1 : 10,
|
||||
delay: dto.scheduledFor ? Date.parse(dto.scheduledFor) - Date.now() : 0,
|
||||
});
|
||||
|
||||
return { jobId: job.id };
|
||||
}
|
||||
|
||||
async getJobStatus(jobId: string): Promise<JobStatus> {
|
||||
const job = await this.reportsQueue.getJob(jobId);
|
||||
return {
|
||||
status: await job.getState(),
|
||||
progress: job.progress,
|
||||
result: job.returnvalue,
|
||||
};
|
||||
}
|
||||
}
|
||||
|
||||
// Consumer: Process jobs
|
||||
@Processor('reports')
|
||||
export class ReportsProcessor {
|
||||
private readonly logger = new Logger(ReportsProcessor.name);
|
||||
|
||||
@Process('generate')
|
||||
async generateReport(job: Job<GenerateReportDto>): Promise<Report> {
|
||||
this.logger.log(`Processing report job ${job.id}`);
|
||||
|
||||
// Update progress
|
||||
await job.updateProgress(10);
|
||||
|
||||
const data = await this.fetchData(job.data);
|
||||
await job.updateProgress(50);
|
||||
|
||||
const report = await this.processData(data);
|
||||
await job.updateProgress(90);
|
||||
|
||||
await this.saveReport(report);
|
||||
await job.updateProgress(100);
|
||||
|
||||
return report;
|
||||
}
|
||||
|
||||
@OnQueueActive()
|
||||
onActive(job: Job) {
|
||||
this.logger.log(`Processing job ${job.id}`);
|
||||
}
|
||||
|
||||
@OnQueueCompleted()
|
||||
onCompleted(job: Job, result: any) {
|
||||
this.logger.log(`Job ${job.id} completed`);
|
||||
}
|
||||
|
||||
@OnQueueFailed()
|
||||
onFailed(job: Job, error: Error) {
|
||||
this.logger.error(`Job ${job.id} failed: ${error.message}`);
|
||||
}
|
||||
}
|
||||
|
||||
// Email queue with retry
|
||||
@Processor('email')
|
||||
export class EmailProcessor {
|
||||
@Process('send')
|
||||
async sendEmail(job: Job<SendEmailDto>): Promise<void> {
|
||||
const { to, template, data } = job.data;
|
||||
|
||||
try {
|
||||
await this.mailer.send({
|
||||
to,
|
||||
template,
|
||||
context: data,
|
||||
});
|
||||
} catch (error) {
|
||||
// BullMQ will retry based on job options
|
||||
throw error;
|
||||
}
|
||||
}
|
||||
}
|
||||
|
||||
// Usage
|
||||
@Injectable()
|
||||
export class NotificationService {
|
||||
constructor(@InjectQueue('email') private emailQueue: Queue) {}
|
||||
|
||||
async sendWelcome(user: User): Promise<void> {
|
||||
await this.emailQueue.add(
|
||||
'send',
|
||||
{
|
||||
to: user.email,
|
||||
template: 'welcome',
|
||||
data: { name: user.name },
|
||||
},
|
||||
{
|
||||
attempts: 5,
|
||||
backoff: { type: 'exponential', delay: 5000 },
|
||||
},
|
||||
);
|
||||
}
|
||||
}
|
||||
|
||||
// Scheduled jobs
|
||||
@Injectable()
|
||||
export class ScheduledJobsService implements OnModuleInit {
|
||||
constructor(@InjectQueue('maintenance') private queue: Queue) {}
|
||||
|
||||
async onModuleInit(): Promise<void> {
|
||||
// Clean up old reports daily at midnight
|
||||
await this.queue.add(
|
||||
'cleanup',
|
||||
{},
|
||||
{
|
||||
repeat: { cron: '0 0 * * *' },
|
||||
jobId: 'daily-cleanup', // Prevent duplicates
|
||||
},
|
||||
);
|
||||
|
||||
// Send digest every hour
|
||||
await this.queue.add(
|
||||
'digest',
|
||||
{},
|
||||
{
|
||||
repeat: { every: 60 * 60 * 1000 },
|
||||
jobId: 'hourly-digest',
|
||||
},
|
||||
);
|
||||
}
|
||||
}
|
||||
|
||||
@Processor('maintenance')
|
||||
export class MaintenanceProcessor {
|
||||
@Process('cleanup')
|
||||
async cleanup(): Promise<void> {
|
||||
await this.cleanupOldReports();
|
||||
await this.cleanupExpiredSessions();
|
||||
}
|
||||
|
||||
@Process('digest')
|
||||
async sendDigest(): Promise<void> {
|
||||
const users = await this.getUsersForDigest();
|
||||
for (const user of users) {
|
||||
await this.emailQueue.add('send', { to: user.email, template: 'digest' });
|
||||
}
|
||||
}
|
||||
}
|
||||
|
||||
// Queue monitoring with Bull Board
|
||||
import { BullBoardModule } from '@bull-board/nestjs';
|
||||
import { BullMQAdapter } from '@bull-board/api/bullMQAdapter';
|
||||
|
||||
@Module({
|
||||
imports: [
|
||||
BullBoardModule.forRoot({
|
||||
route: '/admin/queues',
|
||||
adapter: ExpressAdapter,
|
||||
}),
|
||||
BullBoardModule.forFeature({
|
||||
name: 'email',
|
||||
adapter: BullMQAdapter,
|
||||
}),
|
||||
BullBoardModule.forFeature({
|
||||
name: 'reports',
|
||||
adapter: BullMQAdapter,
|
||||
}),
|
||||
],
|
||||
})
|
||||
export class AdminModule {}
|
||||
```
|
||||
|
||||
Reference: [NestJS Queues](https://docs.nestjs.com/techniques/queues)
|
||||
@@ -0,0 +1,109 @@
|
||||
---
|
||||
title: Use Async Lifecycle Hooks Correctly
|
||||
impact: HIGH
|
||||
impactDescription: Improper async handling blocks application startup
|
||||
tags: performance, lifecycle, async, hooks
|
||||
---
|
||||
|
||||
## Use Async Lifecycle Hooks Correctly
|
||||
|
||||
NestJS lifecycle hooks (`onModuleInit`, `onApplicationBootstrap`, etc.) support async operations. However, misusing them can block application startup or cause race conditions. Understand the lifecycle order and use hooks appropriately.
|
||||
|
||||
**Incorrect (fire-and-forget async without await):**
|
||||
|
||||
```typescript
|
||||
// Fire-and-forget async without await
|
||||
@Injectable()
|
||||
export class DatabaseService implements OnModuleInit {
|
||||
onModuleInit() {
|
||||
// This runs but doesn't block - app starts before DB is ready!
|
||||
this.connect();
|
||||
}
|
||||
|
||||
private async connect() {
|
||||
await this.pool.connect();
|
||||
console.log('Database connected');
|
||||
}
|
||||
}
|
||||
|
||||
// Heavy blocking operations in constructor
|
||||
@Injectable()
|
||||
export class ConfigService {
|
||||
private config: Config;
|
||||
|
||||
constructor() {
|
||||
// BLOCKS entire module instantiation synchronously
|
||||
this.config = fs.readFileSync('config.json');
|
||||
}
|
||||
}
|
||||
```
|
||||
|
||||
**Correct (return promises from async hooks):**
|
||||
|
||||
```typescript
|
||||
// Return promise from async hooks
|
||||
@Injectable()
|
||||
export class DatabaseService implements OnModuleInit {
|
||||
private pool: Pool;
|
||||
|
||||
async onModuleInit(): Promise<void> {
|
||||
// NestJS waits for this to complete before continuing
|
||||
await this.pool.connect();
|
||||
console.log('Database connected');
|
||||
}
|
||||
|
||||
async onModuleDestroy(): Promise<void> {
|
||||
// Clean up resources on shutdown
|
||||
await this.pool.end();
|
||||
console.log('Database disconnected');
|
||||
}
|
||||
}
|
||||
|
||||
// Use onApplicationBootstrap for cross-module dependencies
|
||||
@Injectable()
|
||||
export class CacheWarmerService implements OnApplicationBootstrap {
|
||||
constructor(
|
||||
private cache: CacheService,
|
||||
private products: ProductsService,
|
||||
) {}
|
||||
|
||||
async onApplicationBootstrap(): Promise<void> {
|
||||
// All modules are initialized, safe to warm cache
|
||||
const products = await this.products.findPopular();
|
||||
await this.cache.warmup(products);
|
||||
}
|
||||
}
|
||||
|
||||
// Heavy init in async hooks, not constructor
|
||||
@Injectable()
|
||||
export class ConfigService implements OnModuleInit {
|
||||
private config: Config;
|
||||
|
||||
constructor() {
|
||||
// Keep constructor synchronous and fast
|
||||
}
|
||||
|
||||
async onModuleInit(): Promise<void> {
|
||||
// Async loading in lifecycle hook
|
||||
this.config = await this.loadConfig();
|
||||
}
|
||||
|
||||
private async loadConfig(): Promise<Config> {
|
||||
const file = await fs.promises.readFile('config.json');
|
||||
return JSON.parse(file.toString());
|
||||
}
|
||||
|
||||
get<T>(key: string): T {
|
||||
return this.config[key];
|
||||
}
|
||||
}
|
||||
|
||||
// Enable shutdown hooks in main.ts
|
||||
async function bootstrap() {
|
||||
const app = await NestFactory.create(AppModule);
|
||||
app.enableShutdownHooks(); // Enable SIGTERM/SIGINT handling
|
||||
await app.listen(3000);
|
||||
}
|
||||
```
|
||||
|
||||
Reference: [NestJS Lifecycle Events](https://docs.nestjs.com/fundamentals/lifecycle-events)
|
||||
@@ -0,0 +1,121 @@
|
||||
---
|
||||
title: Use Lazy Loading for Large Modules
|
||||
impact: MEDIUM
|
||||
impactDescription: Improves startup time for large applications
|
||||
tags: performance, lazy-loading, modules, optimization
|
||||
---
|
||||
|
||||
## Use Lazy Loading for Large Modules
|
||||
|
||||
NestJS supports lazy-loading modules, which defers initialization until first use. This is valuable for large applications where some features are rarely used, serverless deployments where cold start time matters, or when certain modules have heavy initialization costs.
|
||||
|
||||
**Incorrect (loading everything eagerly):**
|
||||
|
||||
```typescript
|
||||
// Load everything eagerly in a large app
|
||||
@Module({
|
||||
imports: [
|
||||
UsersModule,
|
||||
OrdersModule,
|
||||
PaymentsModule,
|
||||
ReportsModule, // Heavy, rarely used
|
||||
AnalyticsModule, // Heavy, rarely used
|
||||
AdminModule, // Only admins use this
|
||||
LegacyModule, // Migration module, rarely used
|
||||
BulkImportModule, // Used once a month
|
||||
],
|
||||
})
|
||||
export class AppModule {}
|
||||
|
||||
// All modules initialize at startup, even if never used
|
||||
// Slow cold starts in serverless
|
||||
// Memory wasted on unused modules
|
||||
```
|
||||
|
||||
**Correct (lazy load rarely-used modules):**
|
||||
|
||||
```typescript
|
||||
// Use LazyModuleLoader for optional modules
|
||||
import { LazyModuleLoader } from '@nestjs/core';
|
||||
|
||||
@Injectable()
|
||||
export class ReportsService {
|
||||
constructor(private lazyModuleLoader: LazyModuleLoader) {}
|
||||
|
||||
async generateReport(type: string): Promise<Report> {
|
||||
// Load module only when needed
|
||||
const { ReportsModule } = await import('./reports/reports.module');
|
||||
const moduleRef = await this.lazyModuleLoader.load(() => ReportsModule);
|
||||
|
||||
const reportsService = moduleRef.get(ReportsGeneratorService);
|
||||
return reportsService.generate(type);
|
||||
}
|
||||
}
|
||||
|
||||
// Lazy load admin features with caching
|
||||
@Injectable()
|
||||
export class AdminService {
|
||||
private adminModule: ModuleRef | null = null;
|
||||
|
||||
constructor(private lazyModuleLoader: LazyModuleLoader) {}
|
||||
|
||||
private async getAdminModule(): Promise<ModuleRef> {
|
||||
if (!this.adminModule) {
|
||||
const { AdminModule } = await import('./admin/admin.module');
|
||||
this.adminModule = await this.lazyModuleLoader.load(() => AdminModule);
|
||||
}
|
||||
return this.adminModule;
|
||||
}
|
||||
|
||||
async runAdminTask(task: string): Promise<void> {
|
||||
const moduleRef = await this.getAdminModule();
|
||||
const taskRunner = moduleRef.get(AdminTaskRunner);
|
||||
await taskRunner.run(task);
|
||||
}
|
||||
}
|
||||
|
||||
// Reusable lazy loader service
|
||||
@Injectable()
|
||||
export class ModuleLoaderService {
|
||||
private loadedModules = new Map<string, ModuleRef>();
|
||||
|
||||
constructor(private lazyModuleLoader: LazyModuleLoader) {}
|
||||
|
||||
async load<T>(
|
||||
key: string,
|
||||
importFn: () => Promise<{ default: Type<T> } | Type<T>>,
|
||||
): Promise<ModuleRef> {
|
||||
if (!this.loadedModules.has(key)) {
|
||||
const module = await importFn();
|
||||
const moduleType = 'default' in module ? module.default : module;
|
||||
const moduleRef = await this.lazyModuleLoader.load(() => moduleType);
|
||||
this.loadedModules.set(key, moduleRef);
|
||||
}
|
||||
return this.loadedModules.get(key)!;
|
||||
}
|
||||
}
|
||||
|
||||
// Preload modules in background after startup
|
||||
@Injectable()
|
||||
export class ModulePreloader implements OnApplicationBootstrap {
|
||||
constructor(private lazyModuleLoader: LazyModuleLoader) {}
|
||||
|
||||
async onApplicationBootstrap(): Promise<void> {
|
||||
setTimeout(async () => {
|
||||
await this.preloadModule(() => import('./reports/reports.module'));
|
||||
}, 5000); // 5 seconds after startup
|
||||
}
|
||||
|
||||
private async preloadModule(importFn: () => Promise<any>): Promise<void> {
|
||||
try {
|
||||
const module = await importFn();
|
||||
const moduleType = module.default || Object.values(module)[0];
|
||||
await this.lazyModuleLoader.load(() => moduleType);
|
||||
} catch (error) {
|
||||
console.warn('Failed to preload module', error);
|
||||
}
|
||||
}
|
||||
}
|
||||
```
|
||||
|
||||
Reference: [NestJS Lazy Loading Modules](https://docs.nestjs.com/fundamentals/lazy-loading-modules)
|
||||
@@ -0,0 +1,131 @@
|
||||
---
|
||||
title: Optimize Database Queries
|
||||
impact: HIGH
|
||||
impactDescription: Database queries are typically the largest source of latency
|
||||
tags: performance, database, queries, optimization
|
||||
---
|
||||
|
||||
## Optimize Database Queries
|
||||
|
||||
Select only needed columns, use proper indexes, avoid over-fetching relations, and consider query performance when designing your data access. Most API slowness traces back to inefficient database queries.
|
||||
|
||||
**Incorrect (over-fetching data and missing indexes):**
|
||||
|
||||
```typescript
|
||||
// Select everything when you need few fields
|
||||
@Injectable()
|
||||
export class UsersService {
|
||||
async findAllEmails(): Promise<string[]> {
|
||||
const users = await this.repo.find();
|
||||
// Fetches ALL columns for ALL users
|
||||
return users.map((u) => u.email);
|
||||
}
|
||||
|
||||
async getUserSummary(id: string): Promise<UserSummary> {
|
||||
const user = await this.repo.findOne({
|
||||
where: { id },
|
||||
relations: ['posts', 'posts.comments', 'posts.comments.author', 'followers'],
|
||||
});
|
||||
// Over-fetches massive relation tree
|
||||
return { name: user.name, postCount: user.posts.length };
|
||||
}
|
||||
}
|
||||
|
||||
// No indexes on frequently queried columns
|
||||
@Entity()
|
||||
export class Order {
|
||||
@Column()
|
||||
userId: string; // No index - full table scan on every lookup
|
||||
|
||||
@Column()
|
||||
status: string; // No index - slow status filtering
|
||||
}
|
||||
```
|
||||
|
||||
**Correct (select only needed data with proper indexes):**
|
||||
|
||||
```typescript
|
||||
// Select only needed columns
|
||||
@Injectable()
|
||||
export class UsersService {
|
||||
async findAllEmails(): Promise<string[]> {
|
||||
const users = await this.repo.find({
|
||||
select: ['email'], // Only fetch email column
|
||||
});
|
||||
return users.map((u) => u.email);
|
||||
}
|
||||
|
||||
// Use QueryBuilder for complex selections
|
||||
async getUserSummary(id: string): Promise<UserSummary> {
|
||||
return this.repo
|
||||
.createQueryBuilder('user')
|
||||
.select('user.name', 'name')
|
||||
.addSelect('COUNT(post.id)', 'postCount')
|
||||
.leftJoin('user.posts', 'post')
|
||||
.where('user.id = :id', { id })
|
||||
.groupBy('user.id')
|
||||
.getRawOne();
|
||||
}
|
||||
|
||||
// Fetch relations only when needed
|
||||
async getFullProfile(id: string): Promise<User> {
|
||||
return this.repo.findOne({
|
||||
where: { id },
|
||||
relations: ['posts'], // Only immediate relation
|
||||
select: {
|
||||
id: true,
|
||||
name: true,
|
||||
email: true,
|
||||
posts: {
|
||||
id: true,
|
||||
title: true,
|
||||
},
|
||||
},
|
||||
});
|
||||
}
|
||||
}
|
||||
|
||||
// Add indexes on frequently queried columns
|
||||
@Entity()
|
||||
@Index(['userId'])
|
||||
@Index(['status'])
|
||||
@Index(['createdAt'])
|
||||
@Index(['userId', 'status']) // Composite index for common query pattern
|
||||
export class Order {
|
||||
@PrimaryGeneratedColumn('uuid')
|
||||
id: string;
|
||||
|
||||
@Column()
|
||||
userId: string;
|
||||
|
||||
@Column()
|
||||
status: string;
|
||||
|
||||
@CreateDateColumn()
|
||||
createdAt: Date;
|
||||
}
|
||||
|
||||
// Always paginate large datasets
|
||||
@Injectable()
|
||||
export class OrdersService {
|
||||
async findAll(page = 1, limit = 20): Promise<PaginatedResult<Order>> {
|
||||
const [items, total] = await this.repo.findAndCount({
|
||||
skip: (page - 1) * limit,
|
||||
take: limit,
|
||||
order: { createdAt: 'DESC' },
|
||||
});
|
||||
|
||||
return {
|
||||
items,
|
||||
meta: {
|
||||
page,
|
||||
limit,
|
||||
total,
|
||||
totalPages: Math.ceil(total / limit),
|
||||
},
|
||||
};
|
||||
}
|
||||
}
|
||||
```
|
||||
|
||||
Reference: [TypeORM Query Builder](https://typeorm.io/select-query-builder)
|
||||
@@ -0,0 +1,128 @@
|
||||
---
|
||||
title: Use Caching Strategically
|
||||
impact: HIGH
|
||||
impactDescription: Dramatically reduces database load and response times
|
||||
tags: performance, caching, redis, optimization
|
||||
---
|
||||
|
||||
## Use Caching Strategically
|
||||
|
||||
Implement caching for expensive operations, frequently accessed data, and external API calls. Use NestJS CacheModule with appropriate TTLs and cache invalidation strategies. Don't cache everything - focus on high-impact areas.
|
||||
|
||||
**Incorrect (no caching or caching everything):**
|
||||
|
||||
```typescript
|
||||
// No caching for expensive, repeated queries
|
||||
@Injectable()
|
||||
export class ProductsService {
|
||||
async getPopular(): Promise<Product[]> {
|
||||
// Runs complex aggregation query EVERY request
|
||||
return this.productsRepo
|
||||
.createQueryBuilder('p')
|
||||
.leftJoin('p.orders', 'o')
|
||||
.select('p.*, COUNT(o.id) as orderCount')
|
||||
.groupBy('p.id')
|
||||
.orderBy('orderCount', 'DESC')
|
||||
.limit(20)
|
||||
.getMany();
|
||||
}
|
||||
}
|
||||
|
||||
// Cache everything without thought
|
||||
@Injectable()
|
||||
export class UsersService {
|
||||
@CacheKey('users')
|
||||
@CacheTTL(3600)
|
||||
@UseInterceptors(CacheInterceptor)
|
||||
async findAll(): Promise<User[]> {
|
||||
// Caching user list for 1 hour is wrong if data changes frequently
|
||||
return this.usersRepo.find();
|
||||
}
|
||||
}
|
||||
```
|
||||
|
||||
**Correct (strategic caching with proper invalidation):**
|
||||
|
||||
```typescript
|
||||
// Setup caching module
|
||||
@Module({
|
||||
imports: [
|
||||
CacheModule.registerAsync({
|
||||
imports: [ConfigModule],
|
||||
inject: [ConfigService],
|
||||
useFactory: (config: ConfigService) => ({
|
||||
stores: [
|
||||
new KeyvRedis(config.get('REDIS_URL')),
|
||||
],
|
||||
ttl: 60 * 1000, // Default 60s
|
||||
}),
|
||||
}),
|
||||
],
|
||||
})
|
||||
export class AppModule {}
|
||||
|
||||
// Manual caching for granular control
|
||||
@Injectable()
|
||||
export class ProductsService {
|
||||
constructor(
|
||||
@Inject(CACHE_MANAGER) private cache: Cache,
|
||||
private productsRepo: ProductRepository,
|
||||
) {}
|
||||
|
||||
async getPopular(): Promise<Product[]> {
|
||||
const cacheKey = 'products:popular';
|
||||
|
||||
// Try cache first
|
||||
const cached = await this.cache.get<Product[]>(cacheKey);
|
||||
if (cached) return cached;
|
||||
|
||||
// Cache miss - fetch and cache
|
||||
const products = await this.fetchPopularProducts();
|
||||
await this.cache.set(cacheKey, products, 5 * 60 * 1000); // 5 min TTL
|
||||
return products;
|
||||
}
|
||||
|
||||
// Invalidate cache on changes
|
||||
async updateProduct(id: string, dto: UpdateProductDto): Promise<Product> {
|
||||
const product = await this.productsRepo.save({ id, ...dto });
|
||||
await this.cache.del('products:popular'); // Invalidate
|
||||
return product;
|
||||
}
|
||||
}
|
||||
|
||||
// Decorator-based caching with auto-interceptor
|
||||
@Controller('categories')
|
||||
@UseInterceptors(CacheInterceptor)
|
||||
export class CategoriesController {
|
||||
@Get()
|
||||
@CacheTTL(30 * 60 * 1000) // 30 minutes - categories rarely change
|
||||
findAll(): Promise<Category[]> {
|
||||
return this.categoriesService.findAll();
|
||||
}
|
||||
|
||||
@Get(':id')
|
||||
@CacheTTL(60 * 1000) // 1 minute
|
||||
@CacheKey('category')
|
||||
findOne(@Param('id') id: string): Promise<Category> {
|
||||
return this.categoriesService.findOne(id);
|
||||
}
|
||||
}
|
||||
|
||||
// Event-based cache invalidation
|
||||
@Injectable()
|
||||
export class CacheInvalidationService {
|
||||
constructor(@Inject(CACHE_MANAGER) private cache: Cache) {}
|
||||
|
||||
@OnEvent('product.created')
|
||||
@OnEvent('product.updated')
|
||||
@OnEvent('product.deleted')
|
||||
async invalidateProductCaches(event: ProductEvent) {
|
||||
await Promise.all([
|
||||
this.cache.del('products:popular'),
|
||||
this.cache.del(`product:${event.productId}`),
|
||||
]);
|
||||
}
|
||||
}
|
||||
```
|
||||
|
||||
Reference: [NestJS Caching](https://docs.nestjs.com/techniques/caching)
|
||||
@@ -0,0 +1,146 @@
|
||||
---
|
||||
title: Implement Secure JWT Authentication
|
||||
impact: CRITICAL
|
||||
impactDescription: Essential for secure APIs
|
||||
tags: security, jwt, authentication, tokens
|
||||
---
|
||||
|
||||
## Implement Secure JWT Authentication
|
||||
|
||||
Use `@nestjs/jwt` with `@nestjs/passport` for authentication. Store secrets securely, use appropriate token lifetimes, implement refresh tokens, and validate tokens properly. Never expose sensitive data in JWT payloads.
|
||||
|
||||
**Incorrect (insecure JWT implementation):**
|
||||
|
||||
```typescript
|
||||
// Hardcode secrets
|
||||
@Module({
|
||||
imports: [
|
||||
JwtModule.register({
|
||||
secret: 'my-secret-key', // Exposed in code
|
||||
signOptions: { expiresIn: '7d' }, // Too long
|
||||
}),
|
||||
],
|
||||
})
|
||||
export class AuthModule {}
|
||||
|
||||
// Store sensitive data in JWT
|
||||
async login(user: User): Promise<{ accessToken: string }> {
|
||||
const payload = {
|
||||
sub: user.id,
|
||||
email: user.email,
|
||||
password: user.password, // NEVER include password!
|
||||
ssn: user.ssn, // NEVER include sensitive data!
|
||||
isAdmin: user.isAdmin, // Can be tampered if not verified
|
||||
};
|
||||
return { accessToken: this.jwtService.sign(payload) };
|
||||
}
|
||||
|
||||
// Skip token validation
|
||||
@Injectable()
|
||||
export class JwtStrategy extends PassportStrategy(Strategy) {
|
||||
constructor() {
|
||||
super({
|
||||
jwtFromRequest: ExtractJwt.fromAuthHeaderAsBearerToken(),
|
||||
secretOrKey: 'my-secret',
|
||||
});
|
||||
}
|
||||
|
||||
async validate(payload: any): Promise<any> {
|
||||
return payload; // No validation of user existence
|
||||
}
|
||||
}
|
||||
```
|
||||
|
||||
**Correct (secure JWT with refresh tokens):**
|
||||
|
||||
```typescript
|
||||
// Secure JWT configuration
|
||||
@Module({
|
||||
imports: [
|
||||
JwtModule.registerAsync({
|
||||
imports: [ConfigModule],
|
||||
inject: [ConfigService],
|
||||
useFactory: (config: ConfigService) => ({
|
||||
secret: config.get<string>('JWT_SECRET'),
|
||||
signOptions: {
|
||||
expiresIn: '15m', // Short-lived access tokens
|
||||
issuer: config.get<string>('JWT_ISSUER'),
|
||||
audience: config.get<string>('JWT_AUDIENCE'),
|
||||
},
|
||||
}),
|
||||
}),
|
||||
PassportModule.register({ defaultStrategy: 'jwt' }),
|
||||
],
|
||||
})
|
||||
export class AuthModule {}
|
||||
|
||||
// Minimal JWT payload
|
||||
@Injectable()
|
||||
export class AuthService {
|
||||
async login(user: User): Promise<TokenResponse> {
|
||||
// Only include necessary, non-sensitive data
|
||||
const payload: JwtPayload = {
|
||||
sub: user.id,
|
||||
email: user.email,
|
||||
roles: user.roles,
|
||||
iat: Math.floor(Date.now() / 1000),
|
||||
};
|
||||
|
||||
const accessToken = this.jwtService.sign(payload);
|
||||
const refreshToken = await this.createRefreshToken(user.id);
|
||||
|
||||
return { accessToken, refreshToken, expiresIn: 900 };
|
||||
}
|
||||
|
||||
private async createRefreshToken(userId: string): Promise<string> {
|
||||
const token = randomBytes(32).toString('hex');
|
||||
const hashedToken = await bcrypt.hash(token, 10);
|
||||
|
||||
await this.refreshTokenRepo.save({
|
||||
userId,
|
||||
token: hashedToken,
|
||||
expiresAt: new Date(Date.now() + 7 * 24 * 60 * 60 * 1000), // 7 days
|
||||
});
|
||||
|
||||
return token;
|
||||
}
|
||||
}
|
||||
|
||||
// Proper JWT strategy with validation
|
||||
@Injectable()
|
||||
export class JwtStrategy extends PassportStrategy(Strategy) {
|
||||
constructor(
|
||||
private config: ConfigService,
|
||||
private usersService: UsersService,
|
||||
) {
|
||||
super({
|
||||
jwtFromRequest: ExtractJwt.fromAuthHeaderAsBearerToken(),
|
||||
secretOrKey: config.get<string>('JWT_SECRET'),
|
||||
ignoreExpiration: false,
|
||||
issuer: config.get<string>('JWT_ISSUER'),
|
||||
audience: config.get<string>('JWT_AUDIENCE'),
|
||||
});
|
||||
}
|
||||
|
||||
async validate(payload: JwtPayload): Promise<User> {
|
||||
// Verify user still exists and is active
|
||||
const user = await this.usersService.findById(payload.sub);
|
||||
|
||||
if (!user || !user.isActive) {
|
||||
throw new UnauthorizedException('User not found or inactive');
|
||||
}
|
||||
|
||||
// Verify token wasn't issued before password change
|
||||
if (user.passwordChangedAt) {
|
||||
const tokenIssuedAt = new Date(payload.iat * 1000);
|
||||
if (tokenIssuedAt < user.passwordChangedAt) {
|
||||
throw new UnauthorizedException('Token invalidated by password change');
|
||||
}
|
||||
}
|
||||
|
||||
return user;
|
||||
}
|
||||
}
|
||||
```
|
||||
|
||||
Reference: [NestJS Authentication](https://docs.nestjs.com/security/authentication)
|
||||
@@ -0,0 +1,125 @@
|
||||
---
|
||||
title: Implement Rate Limiting
|
||||
impact: HIGH
|
||||
impactDescription: Protects against abuse and ensures fair resource usage
|
||||
tags: security, rate-limiting, throttler, protection
|
||||
---
|
||||
|
||||
## Implement Rate Limiting
|
||||
|
||||
Use `@nestjs/throttler` to limit request rates per client. Apply different limits for different endpoints - stricter for auth endpoints, more relaxed for read operations. Consider using Redis for distributed rate limiting in clustered deployments.
|
||||
|
||||
**Incorrect (no rate limiting on sensitive endpoints):**
|
||||
|
||||
```typescript
|
||||
// No rate limiting on sensitive endpoints
|
||||
@Controller('auth')
|
||||
export class AuthController {
|
||||
@Post('login')
|
||||
async login(@Body() dto: LoginDto): Promise<TokenResponse> {
|
||||
// Attackers can brute-force credentials
|
||||
return this.authService.login(dto);
|
||||
}
|
||||
|
||||
@Post('forgot-password')
|
||||
async forgotPassword(@Body() dto: ForgotPasswordDto): Promise<void> {
|
||||
// Can be abused to spam users with emails
|
||||
return this.authService.sendResetEmail(dto.email);
|
||||
}
|
||||
}
|
||||
|
||||
// Same limits for all endpoints
|
||||
@UseGuards(ThrottlerGuard)
|
||||
@Controller('api')
|
||||
export class ApiController {
|
||||
@Get('public-data')
|
||||
async getPublic() {} // Should allow more requests
|
||||
|
||||
@Post('process-payment')
|
||||
async payment() {} // Should be more restrictive
|
||||
}
|
||||
```
|
||||
|
||||
**Correct (configured throttler with endpoint-specific limits):**
|
||||
|
||||
```typescript
|
||||
// Configure throttler globally with multiple limits
|
||||
import { ThrottlerModule, ThrottlerGuard } from '@nestjs/throttler';
|
||||
|
||||
@Module({
|
||||
imports: [
|
||||
ThrottlerModule.forRoot([
|
||||
{
|
||||
name: 'short',
|
||||
ttl: 1000, // 1 second
|
||||
limit: 3, // 3 requests per second
|
||||
},
|
||||
{
|
||||
name: 'medium',
|
||||
ttl: 10000, // 10 seconds
|
||||
limit: 20, // 20 requests per 10 seconds
|
||||
},
|
||||
{
|
||||
name: 'long',
|
||||
ttl: 60000, // 1 minute
|
||||
limit: 100, // 100 requests per minute
|
||||
},
|
||||
]),
|
||||
],
|
||||
providers: [
|
||||
{
|
||||
provide: APP_GUARD,
|
||||
useClass: ThrottlerGuard,
|
||||
},
|
||||
],
|
||||
})
|
||||
export class AppModule {}
|
||||
|
||||
// Override limits per endpoint
|
||||
@Controller('auth')
|
||||
export class AuthController {
|
||||
@Post('login')
|
||||
@Throttle({ short: { limit: 5, ttl: 60000 } }) // 5 attempts per minute
|
||||
async login(@Body() dto: LoginDto): Promise<TokenResponse> {
|
||||
return this.authService.login(dto);
|
||||
}
|
||||
|
||||
@Post('forgot-password')
|
||||
@Throttle({ short: { limit: 3, ttl: 3600000 } }) // 3 per hour
|
||||
async forgotPassword(@Body() dto: ForgotPasswordDto): Promise<void> {
|
||||
return this.authService.sendResetEmail(dto.email);
|
||||
}
|
||||
}
|
||||
|
||||
// Skip throttling for certain routes
|
||||
@Controller('health')
|
||||
export class HealthController {
|
||||
@Get()
|
||||
@SkipThrottle()
|
||||
check(): string {
|
||||
return 'OK';
|
||||
}
|
||||
}
|
||||
|
||||
// Custom throttle per user type
|
||||
@Injectable()
|
||||
export class CustomThrottlerGuard extends ThrottlerGuard {
|
||||
protected async getTracker(req: Request): Promise<string> {
|
||||
// Use user ID if authenticated, IP otherwise
|
||||
return req.user?.id || req.ip;
|
||||
}
|
||||
|
||||
protected async getLimit(context: ExecutionContext): Promise<number> {
|
||||
const request = context.switchToHttp().getRequest();
|
||||
|
||||
// Higher limits for authenticated users
|
||||
if (request.user) {
|
||||
return request.user.isPremium ? 1000 : 200;
|
||||
}
|
||||
|
||||
return 50; // Anonymous users
|
||||
}
|
||||
}
|
||||
```
|
||||
|
||||
Reference: [NestJS Throttler](https://docs.nestjs.com/security/rate-limiting)
|
||||
@@ -0,0 +1,139 @@
|
||||
---
|
||||
title: Sanitize Output to Prevent XSS
|
||||
impact: HIGH
|
||||
impactDescription: XSS vulnerabilities can compromise user sessions and data
|
||||
tags: security, xss, sanitization, html
|
||||
---
|
||||
|
||||
## Sanitize Output to Prevent XSS
|
||||
|
||||
While NestJS APIs typically return JSON (which browsers don't execute), XSS risks exist when rendering HTML, storing user content, or when frontend frameworks improperly handle API responses. Sanitize user-generated content before storage and use proper Content-Type headers.
|
||||
|
||||
**Incorrect (storing raw HTML without sanitization):**
|
||||
|
||||
```typescript
|
||||
// Store raw HTML from users
|
||||
@Injectable()
|
||||
export class CommentsService {
|
||||
async create(dto: CreateCommentDto): Promise<Comment> {
|
||||
// User can inject: <script>steal(document.cookie)</script>
|
||||
return this.repo.save({
|
||||
content: dto.content, // Raw, unsanitized
|
||||
authorId: dto.authorId,
|
||||
});
|
||||
}
|
||||
}
|
||||
|
||||
// Return HTML without sanitization
|
||||
@Controller('pages')
|
||||
export class PagesController {
|
||||
@Get(':slug')
|
||||
@Header('Content-Type', 'text/html')
|
||||
async getPage(@Param('slug') slug: string): Promise<string> {
|
||||
const page = await this.pagesService.findBySlug(slug);
|
||||
// If page.content contains user input, XSS is possible
|
||||
return `<html><body>${page.content}</body></html>`;
|
||||
}
|
||||
}
|
||||
|
||||
// Reflect user input in errors
|
||||
@Get(':id')
|
||||
async findOne(@Param('id') id: string): Promise<User> {
|
||||
const user = await this.repo.findOne({ where: { id } });
|
||||
if (!user) {
|
||||
// XSS if id contains malicious content and error is rendered
|
||||
throw new NotFoundException(`User ${id} not found`);
|
||||
}
|
||||
return user;
|
||||
}
|
||||
```
|
||||
|
||||
**Correct (sanitize content and use proper headers):**
|
||||
|
||||
```typescript
|
||||
// Sanitize HTML content before storage
|
||||
import * as sanitizeHtml from 'sanitize-html';
|
||||
|
||||
@Injectable()
|
||||
export class CommentsService {
|
||||
private readonly sanitizeOptions: sanitizeHtml.IOptions = {
|
||||
allowedTags: ['b', 'i', 'em', 'strong', 'a', 'p', 'br'],
|
||||
allowedAttributes: {
|
||||
a: ['href', 'title'],
|
||||
},
|
||||
allowedSchemes: ['http', 'https', 'mailto'],
|
||||
};
|
||||
|
||||
async create(dto: CreateCommentDto): Promise<Comment> {
|
||||
return this.repo.save({
|
||||
content: sanitizeHtml(dto.content, this.sanitizeOptions),
|
||||
authorId: dto.authorId,
|
||||
});
|
||||
}
|
||||
}
|
||||
|
||||
// Use validation pipe to strip HTML
|
||||
import { Transform } from 'class-transformer';
|
||||
|
||||
export class CreatePostDto {
|
||||
@IsString()
|
||||
@MaxLength(1000)
|
||||
@Transform(({ value }) => sanitizeHtml(value, { allowedTags: [] }))
|
||||
title: string;
|
||||
|
||||
@IsString()
|
||||
@Transform(({ value }) =>
|
||||
sanitizeHtml(value, {
|
||||
allowedTags: ['p', 'br', 'b', 'i', 'a'],
|
||||
allowedAttributes: { a: ['href'] },
|
||||
}),
|
||||
)
|
||||
content: string;
|
||||
}
|
||||
|
||||
// Set proper Content-Type headers
|
||||
@Controller('api')
|
||||
export class ApiController {
|
||||
@Get('data')
|
||||
@Header('Content-Type', 'application/json')
|
||||
async getData(): Promise<DataResponse> {
|
||||
// JSON response - browser won't execute scripts
|
||||
return this.service.getData();
|
||||
}
|
||||
}
|
||||
|
||||
// Sanitize error messages
|
||||
@Get(':id')
|
||||
async findOne(@Param('id', ParseUUIDPipe) id: string): Promise<User> {
|
||||
const user = await this.repo.findOne({ where: { id } });
|
||||
if (!user) {
|
||||
// UUID validation ensures safe format
|
||||
throw new NotFoundException('User not found');
|
||||
}
|
||||
return user;
|
||||
}
|
||||
|
||||
// Use Helmet for CSP headers
|
||||
import helmet from 'helmet';
|
||||
|
||||
async function bootstrap() {
|
||||
const app = await NestFactory.create(AppModule);
|
||||
|
||||
app.use(
|
||||
helmet({
|
||||
contentSecurityPolicy: {
|
||||
directives: {
|
||||
defaultSrc: ["'self'"],
|
||||
scriptSrc: ["'self'"],
|
||||
styleSrc: ["'self'", "'unsafe-inline'"],
|
||||
imgSrc: ["'self'", 'data:', 'https:'],
|
||||
},
|
||||
},
|
||||
}),
|
||||
);
|
||||
|
||||
await app.listen(3000);
|
||||
}
|
||||
```
|
||||
|
||||
Reference: [OWASP XSS Prevention](https://cheatsheetseries.owasp.org/cheatsheets/Cross_Site_Scripting_Prevention_Cheat_Sheet.html)
|
||||
@@ -0,0 +1,135 @@
|
||||
---
|
||||
title: Use Guards for Authentication and Authorization
|
||||
impact: HIGH
|
||||
impactDescription: Enforces access control before handlers execute
|
||||
tags: security, guards, authentication, authorization
|
||||
---
|
||||
|
||||
## Use Guards for Authentication and Authorization
|
||||
|
||||
Guards determine whether a request should be handled based on authentication state, roles, permissions, or other conditions. They run after middleware but before pipes and interceptors, making them ideal for access control. Use guards instead of manual checks in controllers.
|
||||
|
||||
**Incorrect (manual auth checks in every handler):**
|
||||
|
||||
```typescript
|
||||
// Manual auth checks in every handler
|
||||
@Controller('admin')
|
||||
export class AdminController {
|
||||
@Get('users')
|
||||
async getUsers(@Request() req) {
|
||||
if (!req.user) {
|
||||
throw new UnauthorizedException();
|
||||
}
|
||||
if (!req.user.roles.includes('admin')) {
|
||||
throw new ForbiddenException();
|
||||
}
|
||||
return this.adminService.getUsers();
|
||||
}
|
||||
|
||||
@Delete('users/:id')
|
||||
async deleteUser(@Request() req, @Param('id') id: string) {
|
||||
if (!req.user) {
|
||||
throw new UnauthorizedException();
|
||||
}
|
||||
if (!req.user.roles.includes('admin')) {
|
||||
throw new ForbiddenException();
|
||||
}
|
||||
return this.adminService.deleteUser(id);
|
||||
}
|
||||
}
|
||||
```
|
||||
|
||||
**Correct (guards with declarative decorators):**
|
||||
|
||||
```typescript
|
||||
// JWT Auth Guard
|
||||
@Injectable()
|
||||
export class JwtAuthGuard implements CanActivate {
|
||||
constructor(
|
||||
private jwtService: JwtService,
|
||||
private reflector: Reflector,
|
||||
) {}
|
||||
|
||||
async canActivate(context: ExecutionContext): Promise<boolean> {
|
||||
// Check for @Public() decorator
|
||||
const isPublic = this.reflector.getAllAndOverride<boolean>('isPublic', [
|
||||
context.getHandler(),
|
||||
context.getClass(),
|
||||
]);
|
||||
if (isPublic) return true;
|
||||
|
||||
const request = context.switchToHttp().getRequest();
|
||||
const token = this.extractToken(request);
|
||||
|
||||
if (!token) {
|
||||
throw new UnauthorizedException('No token provided');
|
||||
}
|
||||
|
||||
try {
|
||||
request.user = await this.jwtService.verifyAsync(token);
|
||||
return true;
|
||||
} catch {
|
||||
throw new UnauthorizedException('Invalid token');
|
||||
}
|
||||
}
|
||||
|
||||
private extractToken(request: Request): string | undefined {
|
||||
const [type, token] = request.headers.authorization?.split(' ') ?? [];
|
||||
return type === 'Bearer' ? token : undefined;
|
||||
}
|
||||
}
|
||||
|
||||
// Roles Guard
|
||||
@Injectable()
|
||||
export class RolesGuard implements CanActivate {
|
||||
constructor(private reflector: Reflector) {}
|
||||
|
||||
canActivate(context: ExecutionContext): boolean {
|
||||
const requiredRoles = this.reflector.getAllAndOverride<Role[]>('roles', [
|
||||
context.getHandler(),
|
||||
context.getClass(),
|
||||
]);
|
||||
|
||||
if (!requiredRoles) return true;
|
||||
|
||||
const { user } = context.switchToHttp().getRequest();
|
||||
return requiredRoles.some((role) => user.roles?.includes(role));
|
||||
}
|
||||
}
|
||||
|
||||
// Decorators
|
||||
export const Public = () => SetMetadata('isPublic', true);
|
||||
export const Roles = (...roles: Role[]) => SetMetadata('roles', roles);
|
||||
|
||||
// Register guards globally
|
||||
@Module({
|
||||
providers: [
|
||||
{ provide: APP_GUARD, useClass: JwtAuthGuard },
|
||||
{ provide: APP_GUARD, useClass: RolesGuard },
|
||||
],
|
||||
})
|
||||
export class AppModule {}
|
||||
|
||||
// Clean controller
|
||||
@Controller('admin')
|
||||
@Roles(Role.Admin) // Applied to all routes
|
||||
export class AdminController {
|
||||
@Get('users')
|
||||
getUsers(): Promise<User[]> {
|
||||
return this.adminService.getUsers();
|
||||
}
|
||||
|
||||
@Delete('users/:id')
|
||||
deleteUser(@Param('id') id: string): Promise<void> {
|
||||
return this.adminService.deleteUser(id);
|
||||
}
|
||||
|
||||
@Public() // Override: no auth required
|
||||
@Get('health')
|
||||
health() {
|
||||
return { status: 'ok' };
|
||||
}
|
||||
}
|
||||
```
|
||||
|
||||
Reference: [NestJS Guards](https://docs.nestjs.com/guards)
|
||||
@@ -0,0 +1,150 @@
|
||||
---
|
||||
title: Validate All Input with DTOs and Pipes
|
||||
impact: HIGH
|
||||
impactDescription: First line of defense against attacks
|
||||
tags: security, validation, dto, pipes
|
||||
---
|
||||
|
||||
## Validate All Input with DTOs and Pipes
|
||||
|
||||
Always validate incoming data using class-validator decorators on DTOs and the global ValidationPipe. Never trust user input. Validate all request bodies, query parameters, and route parameters before processing.
|
||||
|
||||
**Incorrect (trust raw input without validation):**
|
||||
|
||||
```typescript
|
||||
// Trust raw input without validation
|
||||
@Controller('users')
|
||||
export class UsersController {
|
||||
@Post()
|
||||
create(@Body() body: any) {
|
||||
// body could contain anything - SQL injection, XSS, etc.
|
||||
return this.usersService.create(body);
|
||||
}
|
||||
|
||||
@Get()
|
||||
findAll(@Query() query: any) {
|
||||
// query.limit could be "'; DROP TABLE users; --"
|
||||
return this.usersService.findAll(query.limit);
|
||||
}
|
||||
}
|
||||
|
||||
// DTOs without validation decorators
|
||||
export class CreateUserDto {
|
||||
name: string; // No validation
|
||||
email: string; // Could be "not-an-email"
|
||||
age: number; // Could be "abc" or -999
|
||||
}
|
||||
```
|
||||
|
||||
**Correct (validated DTOs with global ValidationPipe):**
|
||||
|
||||
```typescript
|
||||
// Enable ValidationPipe globally in main.ts
|
||||
async function bootstrap() {
|
||||
const app = await NestFactory.create(AppModule);
|
||||
|
||||
app.useGlobalPipes(
|
||||
new ValidationPipe({
|
||||
whitelist: true, // Strip unknown properties
|
||||
forbidNonWhitelisted: true, // Throw on unknown properties
|
||||
transform: true, // Auto-transform to DTO types
|
||||
transformOptions: {
|
||||
enableImplicitConversion: true,
|
||||
},
|
||||
}),
|
||||
);
|
||||
|
||||
await app.listen(3000);
|
||||
}
|
||||
|
||||
// Create well-validated DTOs
|
||||
import {
|
||||
IsString,
|
||||
IsEmail,
|
||||
IsInt,
|
||||
Min,
|
||||
Max,
|
||||
IsOptional,
|
||||
MinLength,
|
||||
MaxLength,
|
||||
Matches,
|
||||
IsNotEmpty,
|
||||
} from 'class-validator';
|
||||
import { Transform, Type } from 'class-transformer';
|
||||
|
||||
export class CreateUserDto {
|
||||
@IsString()
|
||||
@IsNotEmpty()
|
||||
@MinLength(2)
|
||||
@MaxLength(100)
|
||||
@Transform(({ value }) => value?.trim())
|
||||
name: string;
|
||||
|
||||
@IsEmail()
|
||||
@Transform(({ value }) => value?.toLowerCase().trim())
|
||||
email: string;
|
||||
|
||||
@IsInt()
|
||||
@Min(0)
|
||||
@Max(150)
|
||||
age: number;
|
||||
|
||||
@IsString()
|
||||
@MinLength(8)
|
||||
@MaxLength(100)
|
||||
@Matches(/^(?=.*[a-z])(?=.*[A-Z])(?=.*\d)/, {
|
||||
message: 'Password must contain uppercase, lowercase, and number',
|
||||
})
|
||||
password: string;
|
||||
}
|
||||
|
||||
// Query DTO with defaults and transformation
|
||||
export class FindUsersQueryDto {
|
||||
@IsOptional()
|
||||
@IsString()
|
||||
@MaxLength(100)
|
||||
search?: string;
|
||||
|
||||
@IsOptional()
|
||||
@Type(() => Number)
|
||||
@IsInt()
|
||||
@Min(1)
|
||||
@Max(100)
|
||||
limit: number = 20;
|
||||
|
||||
@IsOptional()
|
||||
@Type(() => Number)
|
||||
@IsInt()
|
||||
@Min(0)
|
||||
offset: number = 0;
|
||||
}
|
||||
|
||||
// Param validation
|
||||
export class UserIdParamDto {
|
||||
@IsUUID('4')
|
||||
id: string;
|
||||
}
|
||||
|
||||
@Controller('users')
|
||||
export class UsersController {
|
||||
@Post()
|
||||
create(@Body() dto: CreateUserDto): Promise<User> {
|
||||
// dto is guaranteed to be valid
|
||||
return this.usersService.create(dto);
|
||||
}
|
||||
|
||||
@Get()
|
||||
findAll(@Query() query: FindUsersQueryDto): Promise<User[]> {
|
||||
// query.limit is a number, query.search is sanitized
|
||||
return this.usersService.findAll(query);
|
||||
}
|
||||
|
||||
@Get(':id')
|
||||
findOne(@Param() params: UserIdParamDto): Promise<User> {
|
||||
// params.id is a valid UUID
|
||||
return this.usersService.findById(params.id);
|
||||
}
|
||||
}
|
||||
```
|
||||
|
||||
Reference: [NestJS Validation](https://docs.nestjs.com/techniques/validation)
|
||||
@@ -0,0 +1,178 @@
|
||||
---
|
||||
title: Use Supertest for E2E Testing
|
||||
impact: HIGH
|
||||
impactDescription: Validates the full request/response cycle
|
||||
tags: testing, e2e, supertest, integration
|
||||
---
|
||||
|
||||
## Use Supertest for E2E Testing
|
||||
|
||||
End-to-end tests use Supertest to make real HTTP requests against your NestJS application. They test the full stack including middleware, guards, pipes, and interceptors. E2E tests catch integration issues that unit tests miss.
|
||||
|
||||
**Incorrect (no proper E2E setup or teardown):**
|
||||
|
||||
```typescript
|
||||
// Only unit test controllers
|
||||
describe('UsersController', () => {
|
||||
it('should return users', async () => {
|
||||
const service = { findAll: jest.fn().mockResolvedValue([]) };
|
||||
const controller = new UsersController(service as any);
|
||||
|
||||
const result = await controller.findAll();
|
||||
|
||||
expect(result).toEqual([]);
|
||||
// Doesn't test: routes, guards, pipes, serialization
|
||||
});
|
||||
});
|
||||
|
||||
// E2E tests without proper setup/teardown
|
||||
describe('Users API', () => {
|
||||
it('should create user', async () => {
|
||||
const app = await NestFactory.create(AppModule);
|
||||
// No proper initialization
|
||||
// No cleanup after test
|
||||
// Hits real database
|
||||
});
|
||||
});
|
||||
```
|
||||
|
||||
**Correct (proper E2E setup with Supertest):**
|
||||
|
||||
```typescript
|
||||
// Proper E2E test setup
|
||||
import { Test, TestingModule } from '@nestjs/testing';
|
||||
import { INestApplication, ValidationPipe } from '@nestjs/common';
|
||||
import * as request from 'supertest';
|
||||
import { AppModule } from '../src/app.module';
|
||||
|
||||
describe('UsersController (e2e)', () => {
|
||||
let app: INestApplication;
|
||||
|
||||
beforeAll(async () => {
|
||||
const moduleFixture: TestingModule = await Test.createTestingModule({
|
||||
imports: [AppModule],
|
||||
}).compile();
|
||||
|
||||
app = moduleFixture.createNestApplication();
|
||||
|
||||
// Apply same config as production
|
||||
app.useGlobalPipes(
|
||||
new ValidationPipe({
|
||||
whitelist: true,
|
||||
transform: true,
|
||||
forbidNonWhitelisted: true,
|
||||
}),
|
||||
);
|
||||
|
||||
await app.init();
|
||||
});
|
||||
|
||||
afterAll(async () => {
|
||||
await app.close();
|
||||
});
|
||||
|
||||
describe('/users (POST)', () => {
|
||||
it('should create a user', () => {
|
||||
return request(app.getHttpServer())
|
||||
.post('/users')
|
||||
.send({ name: 'John', email: 'john@test.com' })
|
||||
.expect(201)
|
||||
.expect((res) => {
|
||||
expect(res.body).toHaveProperty('id');
|
||||
expect(res.body.name).toBe('John');
|
||||
expect(res.body.email).toBe('john@test.com');
|
||||
});
|
||||
});
|
||||
|
||||
it('should return 400 for invalid email', () => {
|
||||
return request(app.getHttpServer())
|
||||
.post('/users')
|
||||
.send({ name: 'John', email: 'invalid-email' })
|
||||
.expect(400)
|
||||
.expect((res) => {
|
||||
expect(res.body.message).toContain('email');
|
||||
});
|
||||
});
|
||||
});
|
||||
|
||||
describe('/users/:id (GET)', () => {
|
||||
it('should return 404 for non-existent user', () => {
|
||||
return request(app.getHttpServer())
|
||||
.get('/users/non-existent-id')
|
||||
.expect(404);
|
||||
});
|
||||
});
|
||||
});
|
||||
|
||||
// Testing with authentication
|
||||
describe('Protected Routes (e2e)', () => {
|
||||
let app: INestApplication;
|
||||
let authToken: string;
|
||||
|
||||
beforeAll(async () => {
|
||||
const moduleFixture = await Test.createTestingModule({
|
||||
imports: [AppModule],
|
||||
}).compile();
|
||||
|
||||
app = moduleFixture.createNestApplication();
|
||||
app.useGlobalPipes(new ValidationPipe({ whitelist: true }));
|
||||
await app.init();
|
||||
|
||||
// Get auth token
|
||||
const loginResponse = await request(app.getHttpServer())
|
||||
.post('/auth/login')
|
||||
.send({ email: 'test@test.com', password: 'password' });
|
||||
|
||||
authToken = loginResponse.body.accessToken;
|
||||
});
|
||||
|
||||
it('should return 401 without token', () => {
|
||||
return request(app.getHttpServer())
|
||||
.get('/users/me')
|
||||
.expect(401);
|
||||
});
|
||||
|
||||
it('should return user profile with valid token', () => {
|
||||
return request(app.getHttpServer())
|
||||
.get('/users/me')
|
||||
.set('Authorization', `Bearer ${authToken}`)
|
||||
.expect(200)
|
||||
.expect((res) => {
|
||||
expect(res.body.email).toBe('test@test.com');
|
||||
});
|
||||
});
|
||||
});
|
||||
|
||||
// Database isolation for E2E tests
|
||||
describe('Orders API (e2e)', () => {
|
||||
let app: INestApplication;
|
||||
let dataSource: DataSource;
|
||||
|
||||
beforeAll(async () => {
|
||||
const moduleFixture = await Test.createTestingModule({
|
||||
imports: [
|
||||
ConfigModule.forRoot({
|
||||
envFilePath: '.env.test', // Test database config
|
||||
}),
|
||||
AppModule,
|
||||
],
|
||||
}).compile();
|
||||
|
||||
app = moduleFixture.createNestApplication();
|
||||
dataSource = moduleFixture.get(DataSource);
|
||||
await app.init();
|
||||
});
|
||||
|
||||
beforeEach(async () => {
|
||||
// Clean database between tests
|
||||
await dataSource.synchronize(true);
|
||||
});
|
||||
|
||||
afterAll(async () => {
|
||||
await dataSource.destroy();
|
||||
await app.close();
|
||||
});
|
||||
});
|
||||
```
|
||||
|
||||
Reference: [NestJS E2E Testing](https://docs.nestjs.com/fundamentals/testing#end-to-end-testing)
|
||||
@@ -0,0 +1,179 @@
|
||||
---
|
||||
title: Mock External Services in Tests
|
||||
impact: HIGH
|
||||
impactDescription: Ensures fast, reliable, deterministic tests
|
||||
tags: testing, mocking, external-services, jest
|
||||
---
|
||||
|
||||
## Mock External Services in Tests
|
||||
|
||||
Never call real external services (APIs, databases, message queues) in unit tests. Mock them to ensure tests are fast, deterministic, and don't incur costs. Use realistic mock data and test edge cases like timeouts and errors.
|
||||
|
||||
**Incorrect (calling real APIs and databases):**
|
||||
|
||||
```typescript
|
||||
// Call real APIs in tests
|
||||
describe('PaymentService', () => {
|
||||
it('should process payment', async () => {
|
||||
const service = new PaymentService(new StripeClient(realApiKey));
|
||||
// Hits real Stripe API!
|
||||
const result = await service.charge('tok_visa', 1000);
|
||||
// Slow, costs money, flaky
|
||||
});
|
||||
});
|
||||
|
||||
// Use real database
|
||||
describe('UsersService', () => {
|
||||
beforeEach(async () => {
|
||||
await connection.query('DELETE FROM users'); // Modifies real DB
|
||||
});
|
||||
|
||||
it('should create user', async () => {
|
||||
const user = await service.create({ email: 'test@test.com' });
|
||||
// Side effects on shared database
|
||||
});
|
||||
});
|
||||
|
||||
// Incomplete mocks
|
||||
const mockHttpService = {
|
||||
get: jest.fn().mockResolvedValue({ data: {} }),
|
||||
// Missing error scenarios, missing other methods
|
||||
};
|
||||
```
|
||||
|
||||
**Correct (mock all external dependencies):**
|
||||
|
||||
```typescript
|
||||
// Mock HTTP service properly
|
||||
describe('WeatherService', () => {
|
||||
let service: WeatherService;
|
||||
let httpService: jest.Mocked<HttpService>;
|
||||
|
||||
beforeEach(async () => {
|
||||
const module = await Test.createTestingModule({
|
||||
providers: [
|
||||
WeatherService,
|
||||
{
|
||||
provide: HttpService,
|
||||
useValue: {
|
||||
get: jest.fn(),
|
||||
post: jest.fn(),
|
||||
},
|
||||
},
|
||||
],
|
||||
}).compile();
|
||||
|
||||
service = module.get(WeatherService);
|
||||
httpService = module.get(HttpService);
|
||||
});
|
||||
|
||||
it('should return weather data', async () => {
|
||||
const mockResponse = {
|
||||
data: { temperature: 72, humidity: 45 },
|
||||
status: 200,
|
||||
statusText: 'OK',
|
||||
headers: {},
|
||||
config: {},
|
||||
};
|
||||
|
||||
httpService.get.mockReturnValue(of(mockResponse));
|
||||
|
||||
const result = await service.getWeather('NYC');
|
||||
|
||||
expect(result).toEqual({ temperature: 72, humidity: 45 });
|
||||
});
|
||||
|
||||
it('should handle API timeout', async () => {
|
||||
httpService.get.mockReturnValue(
|
||||
throwError(() => new Error('ETIMEDOUT')),
|
||||
);
|
||||
|
||||
await expect(service.getWeather('NYC')).rejects.toThrow('Weather service unavailable');
|
||||
});
|
||||
|
||||
it('should handle rate limiting', async () => {
|
||||
httpService.get.mockReturnValue(
|
||||
throwError(() => ({
|
||||
response: { status: 429, data: { message: 'Rate limited' } },
|
||||
})),
|
||||
);
|
||||
|
||||
await expect(service.getWeather('NYC')).rejects.toThrow(TooManyRequestsException);
|
||||
});
|
||||
});
|
||||
|
||||
// Mock repository instead of database
|
||||
describe('UsersService', () => {
|
||||
let service: UsersService;
|
||||
let repo: jest.Mocked<Repository<User>>;
|
||||
|
||||
beforeEach(async () => {
|
||||
const mockRepo = {
|
||||
find: jest.fn(),
|
||||
findOne: jest.fn(),
|
||||
save: jest.fn(),
|
||||
delete: jest.fn(),
|
||||
createQueryBuilder: jest.fn(),
|
||||
};
|
||||
|
||||
const module = await Test.createTestingModule({
|
||||
providers: [
|
||||
UsersService,
|
||||
{ provide: getRepositoryToken(User), useValue: mockRepo },
|
||||
],
|
||||
}).compile();
|
||||
|
||||
service = module.get(UsersService);
|
||||
repo = module.get(getRepositoryToken(User));
|
||||
});
|
||||
|
||||
it('should find user by id', async () => {
|
||||
const mockUser = { id: '1', name: 'John', email: 'john@test.com' };
|
||||
repo.findOne.mockResolvedValue(mockUser);
|
||||
|
||||
const result = await service.findById('1');
|
||||
|
||||
expect(result).toEqual(mockUser);
|
||||
expect(repo.findOne).toHaveBeenCalledWith({ where: { id: '1' } });
|
||||
});
|
||||
});
|
||||
|
||||
// Create mock factory for complex SDKs
|
||||
function createMockStripe(): jest.Mocked<Stripe> {
|
||||
return {
|
||||
paymentIntents: {
|
||||
create: jest.fn(),
|
||||
retrieve: jest.fn(),
|
||||
confirm: jest.fn(),
|
||||
cancel: jest.fn(),
|
||||
},
|
||||
customers: {
|
||||
create: jest.fn(),
|
||||
retrieve: jest.fn(),
|
||||
},
|
||||
} as any;
|
||||
}
|
||||
|
||||
// Mock time for time-dependent tests
|
||||
describe('TokenService', () => {
|
||||
beforeEach(() => {
|
||||
jest.useFakeTimers();
|
||||
jest.setSystemTime(new Date('2024-01-15'));
|
||||
});
|
||||
|
||||
afterEach(() => {
|
||||
jest.useRealTimers();
|
||||
});
|
||||
|
||||
it('should expire token after 1 hour', async () => {
|
||||
const token = await service.createToken();
|
||||
|
||||
// Fast-forward time
|
||||
jest.advanceTimersByTime(61 * 60 * 1000);
|
||||
|
||||
expect(await service.isValid(token)).toBe(false);
|
||||
});
|
||||
});
|
||||
```
|
||||
|
||||
Reference: [Jest Mocking](https://jestjs.io/docs/mock-functions)
|
||||
@@ -0,0 +1,153 @@
|
||||
---
|
||||
title: Use Testing Module for Unit Tests
|
||||
impact: HIGH
|
||||
impactDescription: Enables proper isolated testing with mocked dependencies
|
||||
tags: testing, unit-tests, mocking, jest
|
||||
---
|
||||
|
||||
## Use Testing Module for Unit Tests
|
||||
|
||||
Use `@nestjs/testing` module to create isolated test environments with mocked dependencies. This ensures your tests run fast, don't depend on external services, and properly test your business logic in isolation.
|
||||
|
||||
**Incorrect (manual instantiation bypassing DI):**
|
||||
|
||||
```typescript
|
||||
// Instantiate services manually without DI
|
||||
describe('UsersService', () => {
|
||||
it('should create user', async () => {
|
||||
// Manual instantiation bypasses DI
|
||||
const repo = new UserRepository(); // Real repo!
|
||||
const service = new UsersService(repo);
|
||||
|
||||
const user = await service.create({ name: 'Test' });
|
||||
// This hits the real database!
|
||||
});
|
||||
});
|
||||
|
||||
// Test implementation details
|
||||
describe('UsersController', () => {
|
||||
it('should call service', async () => {
|
||||
const service = { create: jest.fn() };
|
||||
const controller = new UsersController(service as any);
|
||||
|
||||
await controller.create({ name: 'Test' });
|
||||
|
||||
expect(service.create).toHaveBeenCalled(); // Tests implementation, not behavior
|
||||
});
|
||||
});
|
||||
```
|
||||
|
||||
**Correct (use Test.createTestingModule with mocked dependencies):**
|
||||
|
||||
```typescript
|
||||
// Use Test.createTestingModule for proper DI
|
||||
import { Test, TestingModule } from '@nestjs/testing';
|
||||
|
||||
describe('UsersService', () => {
|
||||
let service: UsersService;
|
||||
let repo: jest.Mocked<UserRepository>;
|
||||
|
||||
beforeEach(async () => {
|
||||
const module: TestingModule = await Test.createTestingModule({
|
||||
providers: [
|
||||
UsersService,
|
||||
{
|
||||
provide: UserRepository,
|
||||
useValue: {
|
||||
save: jest.fn(),
|
||||
findOne: jest.fn(),
|
||||
find: jest.fn(),
|
||||
},
|
||||
},
|
||||
],
|
||||
}).compile();
|
||||
|
||||
service = module.get<UsersService>(UsersService);
|
||||
repo = module.get(UserRepository);
|
||||
});
|
||||
|
||||
afterEach(() => {
|
||||
jest.clearAllMocks();
|
||||
});
|
||||
|
||||
describe('create', () => {
|
||||
it('should save and return user', async () => {
|
||||
const dto = { name: 'John', email: 'john@test.com' };
|
||||
const expectedUser = { id: '1', ...dto };
|
||||
|
||||
repo.save.mockResolvedValue(expectedUser);
|
||||
|
||||
const result = await service.create(dto);
|
||||
|
||||
expect(result).toEqual(expectedUser);
|
||||
expect(repo.save).toHaveBeenCalledWith(dto);
|
||||
});
|
||||
|
||||
it('should throw on duplicate email', async () => {
|
||||
repo.findOne.mockResolvedValue({ id: '1', email: 'test@test.com' });
|
||||
|
||||
await expect(
|
||||
service.create({ name: 'Test', email: 'test@test.com' }),
|
||||
).rejects.toThrow(ConflictException);
|
||||
});
|
||||
});
|
||||
|
||||
describe('findById', () => {
|
||||
it('should return user when found', async () => {
|
||||
const user = { id: '1', name: 'John' };
|
||||
repo.findOne.mockResolvedValue(user);
|
||||
|
||||
const result = await service.findById('1');
|
||||
|
||||
expect(result).toEqual(user);
|
||||
});
|
||||
|
||||
it('should throw NotFoundException when not found', async () => {
|
||||
repo.findOne.mockResolvedValue(null);
|
||||
|
||||
await expect(service.findById('999')).rejects.toThrow(NotFoundException);
|
||||
});
|
||||
});
|
||||
});
|
||||
|
||||
// Testing guards and interceptors
|
||||
describe('RolesGuard', () => {
|
||||
let guard: RolesGuard;
|
||||
let reflector: Reflector;
|
||||
|
||||
beforeEach(async () => {
|
||||
const module = await Test.createTestingModule({
|
||||
providers: [RolesGuard, Reflector],
|
||||
}).compile();
|
||||
|
||||
guard = module.get<RolesGuard>(RolesGuard);
|
||||
reflector = module.get<Reflector>(Reflector);
|
||||
});
|
||||
|
||||
it('should allow when no roles required', () => {
|
||||
const context = createMockExecutionContext({ user: { roles: [] } });
|
||||
jest.spyOn(reflector, 'getAllAndOverride').mockReturnValue(undefined);
|
||||
|
||||
expect(guard.canActivate(context)).toBe(true);
|
||||
});
|
||||
|
||||
it('should allow admin for admin-only route', () => {
|
||||
const context = createMockExecutionContext({ user: { roles: ['admin'] } });
|
||||
jest.spyOn(reflector, 'getAllAndOverride').mockReturnValue(['admin']);
|
||||
|
||||
expect(guard.canActivate(context)).toBe(true);
|
||||
});
|
||||
});
|
||||
|
||||
function createMockExecutionContext(request: Partial<Request>): ExecutionContext {
|
||||
return {
|
||||
switchToHttp: () => ({
|
||||
getRequest: () => request,
|
||||
}),
|
||||
getHandler: () => jest.fn(),
|
||||
getClass: () => jest.fn(),
|
||||
} as ExecutionContext;
|
||||
}
|
||||
```
|
||||
|
||||
Reference: [NestJS Testing](https://docs.nestjs.com/fundamentals/testing)
|
||||
@@ -0,0 +1,212 @@
|
||||
---
|
||||
name: project-guidelines-example
|
||||
description: NestJS modular TDD project guidelines with Drizzle and PostgreSQL. Use when scaffolding features, reviewing structure, or aligning code with this repo's conventions.
|
||||
---
|
||||
|
||||
# Project Guidelines
|
||||
|
||||
Project skill for this NestJS API. Contains architecture, file structure, code patterns, testing, and deployment conventions.
|
||||
|
||||
## When to Use
|
||||
|
||||
Reference this skill when working on this project. It contains:
|
||||
|
||||
- Architecture overview
|
||||
- File structure
|
||||
- Code patterns
|
||||
- Testing requirements
|
||||
- Deployment workflow
|
||||
|
||||
---
|
||||
|
||||
## Architecture Overview
|
||||
|
||||
**Tech Stack:**
|
||||
|
||||
- **Backend**: NestJS
|
||||
- **Database**: PostgreSQL using Drizzle ORM
|
||||
- **Testing**: NestJS TestingModule (unit) and Supertest (E2E)
|
||||
|
||||
---
|
||||
|
||||
## File Structure
|
||||
|
||||
```
|
||||
project/
|
||||
├── src/
|
||||
│ ├── main.ts # Application bootstrap
|
||||
│ ├── app.module.ts # Root module
|
||||
│ ├── common/ # Shared cross-cutting concerns
|
||||
│ │ ├── decorators/
|
||||
│ │ ├── filters/
|
||||
│ │ ├── guards/
|
||||
│ │ ├── interceptors/
|
||||
│ │ └── pipes/
|
||||
│ ├── config/ # Env and database config
|
||||
│ └── modules/ # Feature modules (one folder per domain)
|
||||
│ ├── auth/
|
||||
│ │ ├── auth.module.ts
|
||||
│ │ ├── auth.controller.ts
|
||||
│ │ ├── auth.controller.spec.ts # Unit tests (colocated)
|
||||
│ │ ├── auth.service.ts
|
||||
│ │ ├── auth.service.spec.ts
|
||||
│ │ ├── dto/
|
||||
│ │ └── strategies/
|
||||
│ └── users/
|
||||
│ ├── users.module.ts
|
||||
│ ├── users.controller.ts
|
||||
│ ├── users.controller.spec.ts
|
||||
│ ├── users.service.ts
|
||||
│ ├── users.service.spec.ts
|
||||
│ └── dto/
|
||||
├── test/ # E2E tests (NestJS convention)
|
||||
│ ├── jest-e2e.json
|
||||
│ ├── app.e2e-spec.ts
|
||||
│ ├── auth.e2e-spec.ts
|
||||
│ └── users.e2e-spec.ts
|
||||
├── drizzle/ # Schema and migrations
|
||||
│ ├── schema.ts
|
||||
│ └── migrations/
|
||||
├── drizzle.config.ts # Drizzle Kit config
|
||||
├── deploy/ # Deployment configs
|
||||
├── docs/ # Documentation
|
||||
└── scripts/ # Utility scripts
|
||||
```
|
||||
|
||||
---
|
||||
|
||||
## Code Patterns
|
||||
|
||||
### Controller + DTO
|
||||
|
||||
```typescript
|
||||
export class CreateUserDto {
|
||||
@IsEmail()
|
||||
email: string;
|
||||
|
||||
@IsString()
|
||||
@MinLength(8)
|
||||
password: string;
|
||||
}
|
||||
|
||||
@Controller('users')
|
||||
export class UsersController {
|
||||
constructor(private readonly usersService: UsersService) {}
|
||||
|
||||
@Post()
|
||||
create(@Body() dto: CreateUserDto) {
|
||||
return this.usersService.create(dto);
|
||||
}
|
||||
}
|
||||
```
|
||||
|
||||
### Drizzle Repository
|
||||
|
||||
```typescript
|
||||
@Injectable()
|
||||
export class UsersRepository {
|
||||
constructor(@Inject(DRIZZLE) private readonly db: DrizzleDB) {}
|
||||
|
||||
findById(id: string) {
|
||||
return this.db.query.users.findFirst({
|
||||
where: eq(users.id, id),
|
||||
});
|
||||
}
|
||||
|
||||
create(data: typeof users.$inferInsert) {
|
||||
return this.db.insert(users).values(data).returning();
|
||||
}
|
||||
}
|
||||
```
|
||||
|
||||
---
|
||||
|
||||
## Testing Requirements
|
||||
|
||||
```bash
|
||||
# Unit tests
|
||||
npm test
|
||||
|
||||
# Coverage
|
||||
npm run test:cov
|
||||
|
||||
# E2E
|
||||
npm run test:e2e
|
||||
```
|
||||
|
||||
**Unit test (colocated `*.spec.ts`):**
|
||||
|
||||
```typescript
|
||||
const moduleRef = await Test.createTestingModule({
|
||||
providers: [
|
||||
UsersService,
|
||||
{ provide: UsersRepository, useValue: { findById: jest.fn() } },
|
||||
],
|
||||
}).compile();
|
||||
|
||||
const service = moduleRef.get(UsersService);
|
||||
```
|
||||
|
||||
**E2E test (`test/*.e2e-spec.ts`):**
|
||||
|
||||
```typescript
|
||||
describe('UsersController (e2e)', () => {
|
||||
it('/users (POST)', () => {
|
||||
return request(app.getHttpServer())
|
||||
.post('/users')
|
||||
.send({ email: 'ada@example.com', password: 'secret123' })
|
||||
.expect(201);
|
||||
});
|
||||
});
|
||||
```
|
||||
|
||||
---
|
||||
|
||||
## Deployment Workflow
|
||||
|
||||
### Pre-Deployment Checklist
|
||||
|
||||
- [ ] All tests passing locally
|
||||
- [ ] `npm run build` succeeds
|
||||
- [ ] `npm run test:e2e` passes
|
||||
- [ ] No hardcoded secrets
|
||||
- [ ] Environment variables documented
|
||||
- [ ] Drizzle migrations applied
|
||||
|
||||
### Deployment Commands
|
||||
|
||||
```bash
|
||||
npm run build
|
||||
npx drizzle-kit migrate
|
||||
# deploy the NestJS API (Cloud Run, Fly, or similar)
|
||||
```
|
||||
|
||||
### Environment Variables
|
||||
|
||||
```bash
|
||||
DATABASE_URL=postgresql://user:pass@host:5432/tracking
|
||||
PORT=3000
|
||||
JWT_SECRET=...
|
||||
```
|
||||
|
||||
---
|
||||
|
||||
## Critical Rules
|
||||
|
||||
1. **No emojis** in code, comments, or documentation
|
||||
2. **Immutability** - never mutate objects or arrays
|
||||
3. **TDD** - write tests before implementation
|
||||
4. **80% coverage** minimum
|
||||
5. **Many small files** - 200-400 lines typical, 800 max
|
||||
6. **No console.log** in production code
|
||||
7. **Exception filters** for HTTP errors, not raw try/catch in controllers
|
||||
8. **Input validation** with class-validator DTOs
|
||||
|
||||
---
|
||||
|
||||
## Related Skills
|
||||
|
||||
- `.agents/skills/coding-standards/` - General coding best practices
|
||||
- `.agents/skills/backend-patterns/` - API and database patterns
|
||||
- `.agents/skills/nestjs-best-practices/` - NestJS architecture and security
|
||||
- `.agents/skills/tdd-workflow/` - Test-driven development methodology
|
||||
@@ -0,0 +1,494 @@
|
||||
---
|
||||
name: security-review
|
||||
description: Use this skill when adding authentication, handling user input, working with secrets, creating API endpoints, or implementing payment/sensitive features. Provides comprehensive security checklist and patterns.
|
||||
---
|
||||
|
||||
# Security Review Skill
|
||||
|
||||
This skill ensures all code follows security best practices and identifies potential vulnerabilities.
|
||||
|
||||
## When to Activate
|
||||
|
||||
- Implementing authentication or authorization
|
||||
- Handling user input or file uploads
|
||||
- Creating new API endpoints
|
||||
- Working with secrets or credentials
|
||||
- Implementing payment features
|
||||
- Storing or transmitting sensitive data
|
||||
- Integrating third-party APIs
|
||||
|
||||
## Security Checklist
|
||||
|
||||
### 1. Secrets Management
|
||||
|
||||
#### ❌ NEVER Do This
|
||||
```typescript
|
||||
const apiKey = "sk-proj-xxxxx" // Hardcoded secret
|
||||
const dbPassword = "password123" // In source code
|
||||
```
|
||||
|
||||
#### ✅ ALWAYS Do This
|
||||
```typescript
|
||||
const apiKey = process.env.OPENAI_API_KEY
|
||||
const dbUrl = process.env.DATABASE_URL
|
||||
|
||||
// Verify secrets exist
|
||||
if (!apiKey) {
|
||||
throw new Error('OPENAI_API_KEY not configured')
|
||||
}
|
||||
```
|
||||
|
||||
#### Verification Steps
|
||||
- [ ] No hardcoded API keys, tokens, or passwords
|
||||
- [ ] All secrets in environment variables
|
||||
- [ ] `.env.local` in .gitignore
|
||||
- [ ] No secrets in git history
|
||||
- [ ] Production secrets in hosting platform (Vercel, Railway)
|
||||
|
||||
### 2. Input Validation
|
||||
|
||||
#### Always Validate User Input
|
||||
```typescript
|
||||
import { z } from 'zod'
|
||||
|
||||
// Define validation schema
|
||||
const CreateUserSchema = z.object({
|
||||
email: z.string().email(),
|
||||
name: z.string().min(1).max(100),
|
||||
age: z.number().int().min(0).max(150)
|
||||
})
|
||||
|
||||
// Validate before processing
|
||||
export async function createUser(input: unknown) {
|
||||
try {
|
||||
const validated = CreateUserSchema.parse(input)
|
||||
return await db.users.create(validated)
|
||||
} catch (error) {
|
||||
if (error instanceof z.ZodError) {
|
||||
return { success: false, errors: error.errors }
|
||||
}
|
||||
throw error
|
||||
}
|
||||
}
|
||||
```
|
||||
|
||||
#### File Upload Validation
|
||||
```typescript
|
||||
function validateFileUpload(file: File) {
|
||||
// Size check (5MB max)
|
||||
const maxSize = 5 * 1024 * 1024
|
||||
if (file.size > maxSize) {
|
||||
throw new Error('File too large (max 5MB)')
|
||||
}
|
||||
|
||||
// Type check
|
||||
const allowedTypes = ['image/jpeg', 'image/png', 'image/gif']
|
||||
if (!allowedTypes.includes(file.type)) {
|
||||
throw new Error('Invalid file type')
|
||||
}
|
||||
|
||||
// Extension check
|
||||
const allowedExtensions = ['.jpg', '.jpeg', '.png', '.gif']
|
||||
const extension = file.name.toLowerCase().match(/\.[^.]+$/)?.[0]
|
||||
if (!extension || !allowedExtensions.includes(extension)) {
|
||||
throw new Error('Invalid file extension')
|
||||
}
|
||||
|
||||
return true
|
||||
}
|
||||
```
|
||||
|
||||
#### Verification Steps
|
||||
- [ ] All user inputs validated with schemas
|
||||
- [ ] File uploads restricted (size, type, extension)
|
||||
- [ ] No direct use of user input in queries
|
||||
- [ ] Whitelist validation (not blacklist)
|
||||
- [ ] Error messages don't leak sensitive info
|
||||
|
||||
### 3. SQL Injection Prevention
|
||||
|
||||
#### ❌ NEVER Concatenate SQL
|
||||
```typescript
|
||||
// DANGEROUS - SQL Injection vulnerability
|
||||
const query = `SELECT * FROM users WHERE email = '${userEmail}'`
|
||||
await db.query(query)
|
||||
```
|
||||
|
||||
#### ✅ ALWAYS Use Parameterized Queries
|
||||
```typescript
|
||||
// Safe - parameterized query
|
||||
const { data } = await supabase
|
||||
.from('users')
|
||||
.select('*')
|
||||
.eq('email', userEmail)
|
||||
|
||||
// Or with raw SQL
|
||||
await db.query(
|
||||
'SELECT * FROM users WHERE email = $1',
|
||||
[userEmail]
|
||||
)
|
||||
```
|
||||
|
||||
#### Verification Steps
|
||||
- [ ] All database queries use parameterized queries
|
||||
- [ ] No string concatenation in SQL
|
||||
- [ ] ORM/query builder used correctly
|
||||
- [ ] Parameterized queries / Drizzle query builder only
|
||||
|
||||
### 4. Authentication & Authorization
|
||||
|
||||
#### JWT Token Handling
|
||||
```typescript
|
||||
// ❌ WRONG: localStorage (vulnerable to XSS)
|
||||
localStorage.setItem('token', token)
|
||||
|
||||
// ✅ CORRECT: httpOnly cookies
|
||||
res.setHeader('Set-Cookie',
|
||||
`token=${token}; HttpOnly; Secure; SameSite=Strict; Max-Age=3600`)
|
||||
```
|
||||
|
||||
#### Authorization Checks
|
||||
```typescript
|
||||
export async function deleteUser(userId: string, requesterId: string) {
|
||||
// ALWAYS verify authorization first
|
||||
const requester = await db.users.findUnique({
|
||||
where: { id: requesterId }
|
||||
})
|
||||
|
||||
if (requester.role !== 'admin') {
|
||||
return NextResponse.json(
|
||||
{ error: 'Unauthorized' },
|
||||
{ status: 403 }
|
||||
)
|
||||
}
|
||||
|
||||
// Proceed with deletion
|
||||
await db.users.delete({ where: { id: userId } })
|
||||
}
|
||||
```
|
||||
|
||||
#### Database Access Control
|
||||
```sql
|
||||
-- Enable RLS on all tables
|
||||
ALTER TABLE users ENABLE ROW LEVEL SECURITY;
|
||||
|
||||
-- Users can only view their own data
|
||||
CREATE POLICY "Users view own data"
|
||||
ON users FOR SELECT
|
||||
USING (auth.uid() = id);
|
||||
|
||||
-- Users can only update their own data
|
||||
CREATE POLICY "Users update own data"
|
||||
ON users FOR UPDATE
|
||||
USING (auth.uid() = id);
|
||||
```
|
||||
|
||||
#### Verification Steps
|
||||
- [ ] Tokens stored in httpOnly cookies (not localStorage)
|
||||
- [ ] Authorization checks before sensitive operations
|
||||
- [ ] Least-privilege database roles; no client DB access
|
||||
- [ ] Role-based access control implemented
|
||||
- [ ] Session management secure
|
||||
|
||||
### 5. XSS Prevention
|
||||
|
||||
#### Sanitize HTML
|
||||
```typescript
|
||||
import DOMPurify from 'isomorphic-dompurify'
|
||||
|
||||
// ALWAYS sanitize user-provided HTML
|
||||
function renderUserContent(html: string) {
|
||||
const clean = DOMPurify.sanitize(html, {
|
||||
ALLOWED_TAGS: ['b', 'i', 'em', 'strong', 'p'],
|
||||
ALLOWED_ATTR: []
|
||||
})
|
||||
return <div dangerouslySetInnerHTML={{ __html: clean }} />
|
||||
}
|
||||
```
|
||||
|
||||
#### Content Security Policy
|
||||
```typescript
|
||||
// next.config.js
|
||||
const securityHeaders = [
|
||||
{
|
||||
key: 'Content-Security-Policy',
|
||||
value: `
|
||||
default-src 'self';
|
||||
script-src 'self' 'unsafe-eval' 'unsafe-inline';
|
||||
style-src 'self' 'unsafe-inline';
|
||||
img-src 'self' data: https:;
|
||||
font-src 'self';
|
||||
connect-src 'self' https://api.example.com;
|
||||
`.replace(/\s{2,}/g, ' ').trim()
|
||||
}
|
||||
]
|
||||
```
|
||||
|
||||
#### Verification Steps
|
||||
- [ ] User-provided HTML sanitized
|
||||
- [ ] CSP headers configured
|
||||
- [ ] No unvalidated dynamic content rendering
|
||||
- [ ] React's built-in XSS protection used
|
||||
|
||||
### 6. CSRF Protection
|
||||
|
||||
#### CSRF Tokens
|
||||
```typescript
|
||||
import { csrf } from '@/lib/csrf'
|
||||
|
||||
export async function POST(request: Request) {
|
||||
const token = request.headers.get('X-CSRF-Token')
|
||||
|
||||
if (!csrf.verify(token)) {
|
||||
return NextResponse.json(
|
||||
{ error: 'Invalid CSRF token' },
|
||||
{ status: 403 }
|
||||
)
|
||||
}
|
||||
|
||||
// Process request
|
||||
}
|
||||
```
|
||||
|
||||
#### SameSite Cookies
|
||||
```typescript
|
||||
res.setHeader('Set-Cookie',
|
||||
`session=${sessionId}; HttpOnly; Secure; SameSite=Strict`)
|
||||
```
|
||||
|
||||
#### Verification Steps
|
||||
- [ ] CSRF tokens on state-changing operations
|
||||
- [ ] SameSite=Strict on all cookies
|
||||
- [ ] Double-submit cookie pattern implemented
|
||||
|
||||
### 7. Rate Limiting
|
||||
|
||||
#### API Rate Limiting
|
||||
```typescript
|
||||
import rateLimit from 'express-rate-limit'
|
||||
|
||||
const limiter = rateLimit({
|
||||
windowMs: 15 * 60 * 1000, // 15 minutes
|
||||
max: 100, // 100 requests per window
|
||||
message: 'Too many requests'
|
||||
})
|
||||
|
||||
// Apply to routes
|
||||
app.use('/api/', limiter)
|
||||
```
|
||||
|
||||
#### Expensive Operations
|
||||
```typescript
|
||||
// Aggressive rate limiting for searches
|
||||
const searchLimiter = rateLimit({
|
||||
windowMs: 60 * 1000, // 1 minute
|
||||
max: 10, // 10 requests per minute
|
||||
message: 'Too many search requests'
|
||||
})
|
||||
|
||||
app.use('/api/search', searchLimiter)
|
||||
```
|
||||
|
||||
#### Verification Steps
|
||||
- [ ] Rate limiting on all API endpoints
|
||||
- [ ] Stricter limits on expensive operations
|
||||
- [ ] IP-based rate limiting
|
||||
- [ ] User-based rate limiting (authenticated)
|
||||
|
||||
### 8. Sensitive Data Exposure
|
||||
|
||||
#### Logging
|
||||
```typescript
|
||||
// ❌ WRONG: Logging sensitive data
|
||||
console.log('User login:', { email, password })
|
||||
console.log('Payment:', { cardNumber, cvv })
|
||||
|
||||
// ✅ CORRECT: Redact sensitive data
|
||||
console.log('User login:', { email, userId })
|
||||
console.log('Payment:', { last4: card.last4, userId })
|
||||
```
|
||||
|
||||
#### Error Messages
|
||||
```typescript
|
||||
// ❌ WRONG: Exposing internal details
|
||||
catch (error) {
|
||||
return NextResponse.json(
|
||||
{ error: error.message, stack: error.stack },
|
||||
{ status: 500 }
|
||||
)
|
||||
}
|
||||
|
||||
// ✅ CORRECT: Generic error messages
|
||||
catch (error) {
|
||||
console.error('Internal error:', error)
|
||||
return NextResponse.json(
|
||||
{ error: 'An error occurred. Please try again.' },
|
||||
{ status: 500 }
|
||||
)
|
||||
}
|
||||
```
|
||||
|
||||
#### Verification Steps
|
||||
- [ ] No passwords, tokens, or secrets in logs
|
||||
- [ ] Error messages generic for users
|
||||
- [ ] Detailed errors only in server logs
|
||||
- [ ] No stack traces exposed to users
|
||||
|
||||
### 9. Blockchain Security (Solana)
|
||||
|
||||
#### Wallet Verification
|
||||
```typescript
|
||||
import { verify } from '@solana/web3.js'
|
||||
|
||||
async function verifyWalletOwnership(
|
||||
publicKey: string,
|
||||
signature: string,
|
||||
message: string
|
||||
) {
|
||||
try {
|
||||
const isValid = verify(
|
||||
Buffer.from(message),
|
||||
Buffer.from(signature, 'base64'),
|
||||
Buffer.from(publicKey, 'base64')
|
||||
)
|
||||
return isValid
|
||||
} catch (error) {
|
||||
return false
|
||||
}
|
||||
}
|
||||
```
|
||||
|
||||
#### Transaction Verification
|
||||
```typescript
|
||||
async function verifyTransaction(transaction: Transaction) {
|
||||
// Verify recipient
|
||||
if (transaction.to !== expectedRecipient) {
|
||||
throw new Error('Invalid recipient')
|
||||
}
|
||||
|
||||
// Verify amount
|
||||
if (transaction.amount > maxAmount) {
|
||||
throw new Error('Amount exceeds limit')
|
||||
}
|
||||
|
||||
// Verify user has sufficient balance
|
||||
const balance = await getBalance(transaction.from)
|
||||
if (balance < transaction.amount) {
|
||||
throw new Error('Insufficient balance')
|
||||
}
|
||||
|
||||
return true
|
||||
}
|
||||
```
|
||||
|
||||
#### Verification Steps
|
||||
- [ ] Wallet signatures verified
|
||||
- [ ] Transaction details validated
|
||||
- [ ] Balance checks before transactions
|
||||
- [ ] No blind transaction signing
|
||||
|
||||
### 10. Dependency Security
|
||||
|
||||
#### Regular Updates
|
||||
```bash
|
||||
# Check for vulnerabilities
|
||||
npm audit
|
||||
|
||||
# Fix automatically fixable issues
|
||||
npm audit fix
|
||||
|
||||
# Update dependencies
|
||||
npm update
|
||||
|
||||
# Check for outdated packages
|
||||
npm outdated
|
||||
```
|
||||
|
||||
#### Lock Files
|
||||
```bash
|
||||
# ALWAYS commit lock files
|
||||
git add package-lock.json
|
||||
|
||||
# Use in CI/CD for reproducible builds
|
||||
npm ci # Instead of npm install
|
||||
```
|
||||
|
||||
#### Verification Steps
|
||||
- [ ] Dependencies up to date
|
||||
- [ ] No known vulnerabilities (npm audit clean)
|
||||
- [ ] Lock files committed
|
||||
- [ ] Dependabot enabled on GitHub
|
||||
- [ ] Regular security updates
|
||||
|
||||
## Security Testing
|
||||
|
||||
### Automated Security Tests
|
||||
```typescript
|
||||
// Test authentication
|
||||
test('requires authentication', async () => {
|
||||
const response = await fetch('/api/protected')
|
||||
expect(response.status).toBe(401)
|
||||
})
|
||||
|
||||
// Test authorization
|
||||
test('requires admin role', async () => {
|
||||
const response = await fetch('/api/admin', {
|
||||
headers: { Authorization: `Bearer ${userToken}` }
|
||||
})
|
||||
expect(response.status).toBe(403)
|
||||
})
|
||||
|
||||
// Test input validation
|
||||
test('rejects invalid input', async () => {
|
||||
const response = await fetch('/api/users', {
|
||||
method: 'POST',
|
||||
body: JSON.stringify({ email: 'not-an-email' })
|
||||
})
|
||||
expect(response.status).toBe(400)
|
||||
})
|
||||
|
||||
// Test rate limiting
|
||||
test('enforces rate limits', async () => {
|
||||
const requests = Array(101).fill(null).map(() =>
|
||||
fetch('/api/endpoint')
|
||||
)
|
||||
|
||||
const responses = await Promise.all(requests)
|
||||
const tooManyRequests = responses.filter(r => r.status === 429)
|
||||
|
||||
expect(tooManyRequests.length).toBeGreaterThan(0)
|
||||
})
|
||||
```
|
||||
|
||||
## Pre-Deployment Security Checklist
|
||||
|
||||
Before ANY production deployment:
|
||||
|
||||
- [ ] **Secrets**: No hardcoded secrets, all in env vars
|
||||
- [ ] **Input Validation**: All user inputs validated
|
||||
- [ ] **SQL Injection**: All queries parameterized
|
||||
- [ ] **XSS**: User content sanitized
|
||||
- [ ] **CSRF**: Protection enabled
|
||||
- [ ] **Authentication**: Proper token handling
|
||||
- [ ] **Authorization**: Role checks in place
|
||||
- [ ] **Rate Limiting**: Enabled on all endpoints
|
||||
- [ ] **HTTPS**: Enforced in production
|
||||
- [ ] **Security Headers**: CSP, X-Frame-Options configured
|
||||
- [ ] **Error Handling**: No sensitive data in errors
|
||||
- [ ] **Logging**: No sensitive data logged
|
||||
- [ ] **Dependencies**: Up to date, no vulnerabilities
|
||||
- [ ] **Least privilege**: App uses a restricted DB role, not a superuser
|
||||
- [ ] **CORS**: Properly configured
|
||||
- [ ] **File Uploads**: Validated (size, type)
|
||||
- [ ] **Wallet Signatures**: Verified (if blockchain)
|
||||
|
||||
## Resources
|
||||
|
||||
- [OWASP Top 10](https://owasp.org/www-project-top-ten/)
|
||||
- [NestJS Security](https://docs.nestjs.com/security/authentication)
|
||||
- [Drizzle ORM](https://orm.drizzle.team/docs/overview)
|
||||
- [Web Security Academy](https://portswigger.net/web-security)
|
||||
|
||||
---
|
||||
|
||||
**Remember**: Security is not optional. One vulnerability can compromise the entire platform. When in doubt, err on the side of caution.
|
||||
@@ -0,0 +1,62 @@
|
||||
---
|
||||
name: strategic-compact
|
||||
description: Suggests manual context compaction at logical intervals to preserve context through task phases rather than arbitrary auto-compaction.
|
||||
---
|
||||
|
||||
# Strategic Compact Skill
|
||||
|
||||
Suggests manual `/compact` at strategic points in your workflow rather than relying on arbitrary auto-compaction.
|
||||
|
||||
## Why Strategic Compaction?
|
||||
|
||||
Auto-compaction triggers at arbitrary points:
|
||||
- Often mid-task, losing important context
|
||||
- No awareness of logical task boundaries
|
||||
- Can interrupt complex multi-step operations
|
||||
|
||||
Strategic compaction at logical boundaries:
|
||||
- **After exploration, before execution** - Compact research context, keep implementation plan
|
||||
- **After completing a milestone** - Fresh start for next phase
|
||||
- **Before major context shifts** - Clear exploration context before different task
|
||||
|
||||
## How It Works
|
||||
|
||||
The `suggest-compact.sh` script runs on PreToolUse (Edit/Write) and:
|
||||
|
||||
1. **Tracks tool calls** - Counts tool invocations in session
|
||||
2. **Threshold detection** - Suggests at configurable threshold (default: 50 calls)
|
||||
3. **Periodic reminders** - Reminds every 25 calls after threshold
|
||||
|
||||
## Hook Setup
|
||||
|
||||
Already wired in `.cursor/hooks.json` as an `afterFileEdit` command:
|
||||
|
||||
```json
|
||||
{
|
||||
"version": 1,
|
||||
"hooks": {
|
||||
"afterFileEdit": [
|
||||
{
|
||||
"command": "node .cursor/scripts/hooks/suggest-compact.js"
|
||||
}
|
||||
]
|
||||
}
|
||||
}
|
||||
```
|
||||
|
||||
## Configuration
|
||||
|
||||
Environment variables:
|
||||
- `COMPACT_THRESHOLD` - Tool calls before first suggestion (default: 50)
|
||||
|
||||
## Best Practices
|
||||
|
||||
1. **Compact after planning** - Once plan is finalized, compact to start fresh
|
||||
2. **Compact after debugging** - Clear error-resolution context before continuing
|
||||
3. **Don't compact mid-implementation** - Preserve context for related changes
|
||||
4. **Read the suggestion** - The hook tells you *when*, you decide *if*
|
||||
|
||||
## Related
|
||||
|
||||
- [The Longform Guide](https://x.com/affaanmustafa/status/2014040193557471352) - Token optimization section
|
||||
- Memory persistence hooks - For state that survives compaction
|
||||
+43
@@ -0,0 +1,43 @@
|
||||
#!/bin/bash
|
||||
# Strategic Compact Suggester
|
||||
# Runs on PreToolUse or periodically to suggest manual compaction at logical intervals
|
||||
#
|
||||
# Why manual over auto-compact:
|
||||
# - Auto-compact happens at arbitrary points, often mid-task
|
||||
# - Strategic compacting preserves context through logical phases
|
||||
# - Compact after exploration, before execution
|
||||
# - Compact after completing a milestone, before starting next
|
||||
#
|
||||
# Configured in .cursor/hooks.json:
|
||||
# afterFileEdit -> node .cursor/scripts/hooks/suggest-compact.js
|
||||
# This shell version is a fallback.
|
||||
#
|
||||
# Criteria for suggesting compact:
|
||||
# - Session has been running for extended period
|
||||
# - Large number of tool calls made
|
||||
# - Transitioning from research/exploration to implementation
|
||||
# - Plan has been finalized
|
||||
|
||||
# Track tool call count (increment in a temp file)
|
||||
COUNTER_FILE="/tmp/claude-tool-count-$$"
|
||||
THRESHOLD=${COMPACT_THRESHOLD:-50}
|
||||
|
||||
# Initialize or increment counter
|
||||
if [ -f "$COUNTER_FILE" ]; then
|
||||
count=$(cat "$COUNTER_FILE")
|
||||
count=$((count + 1))
|
||||
echo "$count" > "$COUNTER_FILE"
|
||||
else
|
||||
echo "1" > "$COUNTER_FILE"
|
||||
count=1
|
||||
fi
|
||||
|
||||
# Suggest compact after threshold tool calls
|
||||
if [ "$count" -eq "$THRESHOLD" ]; then
|
||||
echo "[StrategicCompact] $THRESHOLD tool calls reached - consider /compact if transitioning phases" >&2
|
||||
fi
|
||||
|
||||
# Suggest at regular intervals after threshold
|
||||
if [ "$count" -gt "$THRESHOLD" ] && [ $((count % 25)) -eq 0 ]; then
|
||||
echo "[StrategicCompact] $count tool calls - good checkpoint for /compact if context is stale" >&2
|
||||
fi
|
||||
@@ -0,0 +1,381 @@
|
||||
---
|
||||
name: tdd-workflow
|
||||
description: Use this skill when writing new features, fixing bugs, or refactoring code. Enforces test-driven development with 80%+ coverage including unit, integration, and E2E tests.
|
||||
---
|
||||
|
||||
# Test-Driven Development Workflow
|
||||
|
||||
This skill ensures all code development follows TDD principles with comprehensive test coverage.
|
||||
|
||||
## When to Activate
|
||||
|
||||
- Writing new features or functionality
|
||||
- Fixing bugs or issues
|
||||
- Refactoring existing code
|
||||
- Adding API endpoints
|
||||
- Creating new components
|
||||
|
||||
## Core Principles
|
||||
|
||||
### 1. Tests BEFORE Code
|
||||
ALWAYS write tests first, then implement code to make tests pass.
|
||||
|
||||
### 2. Coverage Requirements
|
||||
- Minimum 80% coverage (unit + integration + E2E)
|
||||
- All edge cases covered
|
||||
- Error scenarios tested
|
||||
- Boundary conditions verified
|
||||
|
||||
### 3. Test Types
|
||||
|
||||
#### Unit Tests
|
||||
- Individual functions and utilities
|
||||
- Component logic
|
||||
- Pure functions
|
||||
- Helpers and utilities
|
||||
|
||||
#### Integration Tests
|
||||
- API endpoints
|
||||
- Database operations
|
||||
- Service interactions
|
||||
- External API calls
|
||||
|
||||
#### E2E Tests (Supertest)
|
||||
- Critical API flows
|
||||
- Complete HTTP workflows
|
||||
- Auth, validation, and error responses
|
||||
|
||||
## TDD Workflow Steps
|
||||
|
||||
### Step 1: Write User Journeys
|
||||
```
|
||||
As a [role], I want to [action], so that [benefit]
|
||||
|
||||
Example:
|
||||
As a user, I want to search for markets semantically,
|
||||
so that I can find relevant markets even without exact keywords.
|
||||
```
|
||||
|
||||
### Step 2: Generate Test Cases
|
||||
For each user journey, create comprehensive test cases:
|
||||
|
||||
```typescript
|
||||
describe('Semantic Search', () => {
|
||||
it('returns relevant markets for query', async () => {
|
||||
// Test implementation
|
||||
})
|
||||
|
||||
it('handles empty query gracefully', async () => {
|
||||
// Test edge case
|
||||
})
|
||||
|
||||
it('falls back to substring search when Redis unavailable', async () => {
|
||||
// Test fallback behavior
|
||||
})
|
||||
|
||||
it('sorts results by similarity score', async () => {
|
||||
// Test sorting logic
|
||||
})
|
||||
})
|
||||
```
|
||||
|
||||
### Step 3: Run Tests (They Should Fail)
|
||||
```bash
|
||||
npm test
|
||||
# Tests should fail - we haven't implemented yet
|
||||
```
|
||||
|
||||
### Step 4: Implement Code
|
||||
Write minimal code to make tests pass:
|
||||
|
||||
```typescript
|
||||
// Implementation guided by tests
|
||||
export async function searchMarkets(query: string) {
|
||||
// Implementation here
|
||||
}
|
||||
```
|
||||
|
||||
### Step 5: Run Tests Again
|
||||
```bash
|
||||
npm test
|
||||
# Tests should now pass
|
||||
```
|
||||
|
||||
### Step 6: Refactor
|
||||
Improve code quality while keeping tests green:
|
||||
- Remove duplication
|
||||
- Improve naming
|
||||
- Optimize performance
|
||||
- Enhance readability
|
||||
|
||||
### Step 7: Verify Coverage
|
||||
```bash
|
||||
npm run test:coverage
|
||||
# Verify 80%+ coverage achieved
|
||||
```
|
||||
|
||||
## Testing Patterns
|
||||
|
||||
### Unit Test Pattern (Jest/Vitest)
|
||||
```typescript
|
||||
import { render, screen, fireEvent } from '@testing-library/react'
|
||||
import { Button } from './Button'
|
||||
|
||||
describe('Button Component', () => {
|
||||
it('renders with correct text', () => {
|
||||
render(<Button>Click me</Button>)
|
||||
expect(screen.getByText('Click me')).toBeInTheDocument()
|
||||
})
|
||||
|
||||
it('calls onClick when clicked', () => {
|
||||
const handleClick = jest.fn()
|
||||
render(<Button onClick={handleClick}>Click</Button>)
|
||||
|
||||
fireEvent.click(screen.getByRole('button'))
|
||||
|
||||
expect(handleClick).toHaveBeenCalledTimes(1)
|
||||
})
|
||||
|
||||
it('is disabled when disabled prop is true', () => {
|
||||
render(<Button disabled>Click</Button>)
|
||||
expect(screen.getByRole('button')).toBeDisabled()
|
||||
})
|
||||
})
|
||||
```
|
||||
|
||||
### API Integration Test Pattern
|
||||
```typescript
|
||||
import { NextRequest } from 'next/server'
|
||||
import { GET } from './route'
|
||||
|
||||
describe('GET /api/markets', () => {
|
||||
it('returns markets successfully', async () => {
|
||||
const request = new NextRequest('http://localhost/api/markets')
|
||||
const response = await GET(request)
|
||||
const data = await response.json()
|
||||
|
||||
expect(response.status).toBe(200)
|
||||
expect(data.success).toBe(true)
|
||||
expect(Array.isArray(data.data)).toBe(true)
|
||||
})
|
||||
|
||||
it('validates query parameters', async () => {
|
||||
const request = new NextRequest('http://localhost/api/markets?limit=invalid')
|
||||
const response = await GET(request)
|
||||
|
||||
expect(response.status).toBe(400)
|
||||
})
|
||||
|
||||
it('handles database errors gracefully', async () => {
|
||||
// Mock database failure
|
||||
const request = new NextRequest('http://localhost/api/markets')
|
||||
// Test error handling
|
||||
})
|
||||
})
|
||||
```
|
||||
|
||||
### E2E Test Pattern (Supertest)
|
||||
```typescript
|
||||
import { INestApplication } from '@nestjs/common'
|
||||
import { Test } from '@nestjs/testing'
|
||||
import request from 'supertest'
|
||||
import { AppModule } from '../src/app.module'
|
||||
|
||||
describe('Users (e2e)', () => {
|
||||
let app: INestApplication
|
||||
|
||||
beforeAll(async () => {
|
||||
const moduleRef = await Test.createTestingModule({
|
||||
imports: [AppModule],
|
||||
}).compile()
|
||||
|
||||
app = moduleRef.createNestApplication()
|
||||
await app.init()
|
||||
})
|
||||
|
||||
afterAll(async () => {
|
||||
await app.close()
|
||||
})
|
||||
|
||||
it('POST /users creates a user', async () => {
|
||||
await request(app.getHttpServer())
|
||||
.post('/users')
|
||||
.send({ email: 'ada@example.com', password: 'secret123' })
|
||||
.expect(201)
|
||||
})
|
||||
})
|
||||
```
|
||||
|
||||
## Test File Organization
|
||||
|
||||
```
|
||||
src/
|
||||
└── modules/
|
||||
└── users/
|
||||
├── users.module.ts
|
||||
├── users.controller.ts
|
||||
├── users.controller.spec.ts # Unit tests
|
||||
├── users.service.ts
|
||||
├── users.service.spec.ts
|
||||
└── dto/
|
||||
test/
|
||||
├── jest-e2e.json
|
||||
├── app.e2e-spec.ts # E2E tests
|
||||
└── users.e2e-spec.ts
|
||||
```
|
||||
|
||||
## Mocking External Services
|
||||
|
||||
### Drizzle Mock
|
||||
```typescript
|
||||
const db = {
|
||||
query: {
|
||||
users: {
|
||||
findFirst: jest.fn(),
|
||||
findMany: jest.fn(),
|
||||
},
|
||||
},
|
||||
insert: jest.fn(),
|
||||
update: jest.fn(),
|
||||
delete: jest.fn(),
|
||||
}
|
||||
```
|
||||
|
||||
### Redis Mock
|
||||
```typescript
|
||||
jest.mock('@/lib/redis', () => ({
|
||||
searchMarketsByVector: jest.fn(() => Promise.resolve([
|
||||
{ slug: 'test-market', similarity_score: 0.95 }
|
||||
])),
|
||||
checkRedisHealth: jest.fn(() => Promise.resolve({ connected: true }))
|
||||
}))
|
||||
```
|
||||
|
||||
### OpenAI Mock
|
||||
```typescript
|
||||
jest.mock('@/lib/openai', () => ({
|
||||
generateEmbedding: jest.fn(() => Promise.resolve(
|
||||
new Array(1536).fill(0.1) // Mock 1536-dim embedding
|
||||
))
|
||||
}))
|
||||
```
|
||||
|
||||
## Test Coverage Verification
|
||||
|
||||
### Run Coverage Report
|
||||
```bash
|
||||
npm run test:coverage
|
||||
```
|
||||
|
||||
### Coverage Thresholds
|
||||
```json
|
||||
{
|
||||
"jest": {
|
||||
"coverageThresholds": {
|
||||
"global": {
|
||||
"branches": 80,
|
||||
"functions": 80,
|
||||
"lines": 80,
|
||||
"statements": 80
|
||||
}
|
||||
}
|
||||
}
|
||||
}
|
||||
```
|
||||
|
||||
## Common Testing Mistakes to Avoid
|
||||
|
||||
### ❌ WRONG: Testing Implementation Details
|
||||
```typescript
|
||||
// Don't test internal state
|
||||
expect(component.state.count).toBe(5)
|
||||
```
|
||||
|
||||
### ✅ CORRECT: Test User-Visible Behavior
|
||||
```typescript
|
||||
// Test what users see
|
||||
expect(screen.getByText('Count: 5')).toBeInTheDocument()
|
||||
```
|
||||
|
||||
### ❌ WRONG: Brittle Selectors
|
||||
```typescript
|
||||
// Breaks easily
|
||||
await page.click('.css-class-xyz')
|
||||
```
|
||||
|
||||
### ✅ CORRECT: Semantic Selectors
|
||||
```typescript
|
||||
// Resilient to changes
|
||||
await page.click('button:has-text("Submit")')
|
||||
await page.click('[data-testid="submit-button"]')
|
||||
```
|
||||
|
||||
### ❌ WRONG: No Test Isolation
|
||||
```typescript
|
||||
// Tests depend on each other
|
||||
test('creates user', () => { /* ... */ })
|
||||
test('updates same user', () => { /* depends on previous test */ })
|
||||
```
|
||||
|
||||
### ✅ CORRECT: Independent Tests
|
||||
```typescript
|
||||
// Each test sets up its own data
|
||||
test('creates user', () => {
|
||||
const user = createTestUser()
|
||||
// Test logic
|
||||
})
|
||||
|
||||
test('updates user', () => {
|
||||
const user = createTestUser()
|
||||
// Update logic
|
||||
})
|
||||
```
|
||||
|
||||
## Continuous Testing
|
||||
|
||||
### Watch Mode During Development
|
||||
```bash
|
||||
npm test -- --watch
|
||||
# Tests run automatically on file changes
|
||||
```
|
||||
|
||||
### Pre-Commit Hook
|
||||
```bash
|
||||
# Runs before every commit
|
||||
npm test && npm run lint
|
||||
```
|
||||
|
||||
### CI/CD Integration
|
||||
```yaml
|
||||
# GitHub Actions
|
||||
- name: Run Tests
|
||||
run: npm test -- --coverage
|
||||
- name: Upload Coverage
|
||||
uses: codecov/codecov-action@v3
|
||||
```
|
||||
|
||||
## Best Practices
|
||||
|
||||
1. **Write Tests First** - Always TDD
|
||||
2. **One Assert Per Test** - Focus on single behavior
|
||||
3. **Descriptive Test Names** - Explain what's tested
|
||||
4. **Arrange-Act-Assert** - Clear test structure
|
||||
5. **Mock External Dependencies** - Isolate unit tests
|
||||
6. **Test Edge Cases** - Null, undefined, empty, large
|
||||
7. **Test Error Paths** - Not just happy paths
|
||||
8. **Keep Tests Fast** - Unit tests < 50ms each
|
||||
9. **Clean Up After Tests** - No side effects
|
||||
10. **Review Coverage Reports** - Identify gaps
|
||||
|
||||
## Success Metrics
|
||||
|
||||
- 80%+ code coverage achieved
|
||||
- All tests passing (green)
|
||||
- No skipped or disabled tests
|
||||
- Fast test execution (< 30s for unit tests)
|
||||
- E2E tests cover critical user flows
|
||||
- Tests catch bugs before production
|
||||
|
||||
---
|
||||
|
||||
**Remember**: Tests are not optional. They are the safety net that enables confident refactoring, rapid development, and production reliability.
|
||||
@@ -0,0 +1,120 @@
|
||||
# Verification Loop Skill
|
||||
|
||||
A comprehensive verification system for Claude Code sessions.
|
||||
|
||||
## When to Use
|
||||
|
||||
Invoke this skill:
|
||||
- After completing a feature or significant code change
|
||||
- Before creating a PR
|
||||
- When you want to ensure quality gates pass
|
||||
- After refactoring
|
||||
|
||||
## Verification Phases
|
||||
|
||||
### Phase 1: Build Verification
|
||||
```bash
|
||||
# Check if project builds
|
||||
npm run build 2>&1 | tail -20
|
||||
# OR
|
||||
pnpm build 2>&1 | tail -20
|
||||
```
|
||||
|
||||
If build fails, STOP and fix before continuing.
|
||||
|
||||
### Phase 2: Type Check
|
||||
```bash
|
||||
# TypeScript projects
|
||||
npx tsc --noEmit 2>&1 | head -30
|
||||
|
||||
# Python projects
|
||||
pyright . 2>&1 | head -30
|
||||
```
|
||||
|
||||
Report all type errors. Fix critical ones before continuing.
|
||||
|
||||
### Phase 3: Lint Check
|
||||
```bash
|
||||
# JavaScript/TypeScript
|
||||
npm run lint 2>&1 | head -30
|
||||
|
||||
# Python
|
||||
ruff check . 2>&1 | head -30
|
||||
```
|
||||
|
||||
### Phase 4: Test Suite
|
||||
```bash
|
||||
# Run tests with coverage
|
||||
npm run test -- --coverage 2>&1 | tail -50
|
||||
|
||||
# Check coverage threshold
|
||||
# Target: 80% minimum
|
||||
```
|
||||
|
||||
Report:
|
||||
- Total tests: X
|
||||
- Passed: X
|
||||
- Failed: X
|
||||
- Coverage: X%
|
||||
|
||||
### Phase 5: Security Scan
|
||||
```bash
|
||||
# Check for secrets
|
||||
grep -rn "sk-" --include="*.ts" --include="*.js" . 2>/dev/null | head -10
|
||||
grep -rn "api_key" --include="*.ts" --include="*.js" . 2>/dev/null | head -10
|
||||
|
||||
# Check for console.log
|
||||
grep -rn "console.log" --include="*.ts" --include="*.tsx" src/ 2>/dev/null | head -10
|
||||
```
|
||||
|
||||
### Phase 6: Diff Review
|
||||
```bash
|
||||
# Show what changed
|
||||
git diff --stat
|
||||
git diff HEAD~1 --name-only
|
||||
```
|
||||
|
||||
Review each changed file for:
|
||||
- Unintended changes
|
||||
- Missing error handling
|
||||
- Potential edge cases
|
||||
|
||||
## Output Format
|
||||
|
||||
After running all phases, produce a verification report:
|
||||
|
||||
```
|
||||
VERIFICATION REPORT
|
||||
==================
|
||||
|
||||
Build: [PASS/FAIL]
|
||||
Types: [PASS/FAIL] (X errors)
|
||||
Lint: [PASS/FAIL] (X warnings)
|
||||
Tests: [PASS/FAIL] (X/Y passed, Z% coverage)
|
||||
Security: [PASS/FAIL] (X issues)
|
||||
Diff: [X files changed]
|
||||
|
||||
Overall: [READY/NOT READY] for PR
|
||||
|
||||
Issues to Fix:
|
||||
1. ...
|
||||
2. ...
|
||||
```
|
||||
|
||||
## Continuous Mode
|
||||
|
||||
For long sessions, run verification every 15 minutes or after major changes:
|
||||
|
||||
```markdown
|
||||
Set a mental checkpoint:
|
||||
- After completing each function
|
||||
- After finishing a component
|
||||
- Before moving to next task
|
||||
|
||||
Run: /verify
|
||||
```
|
||||
|
||||
## Integration with Hooks
|
||||
|
||||
This skill complements PostToolUse hooks but provides deeper verification.
|
||||
Hooks catch issues immediately; this skill provides comprehensive review.
|
||||
Reference in New Issue
Block a user