From 5e55a3617240f7c781c1c95f7fee804430006157 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Philip=20Dub=C3=A9?= <gunkmute@gmail.com>
Date: Thu, 23 Jan 2020 01:52:31 +0000
Subject: [PATCH] Avoid obscuring regression test diffs with normalization

First, diff is updated to not update the files in-place

For some reason diff is being called multiple times,
so $file1.unmodified becomes normalized on second invocation

Secondly, diff-filter updates output to come from the unmodified version

Normalization is serving two purposes:
- avoid diff noise in regressions
- avoid diff noise in commits when expected result is updated

The first purpose only wants to reduce the lines which diff registers,
whereas the second wants those changes to be committed
---
 src/test/regress/bin/diff        | 15 ++++--------
 src/test/regress/bin/diff-filter | 39 ++++++++++++++++++++++++++++++++
 2 files changed, 44 insertions(+), 10 deletions(-)
 create mode 100755 src/test/regress/bin/diff-filter

diff --git a/src/test/regress/bin/diff b/src/test/regress/bin/diff
index 1cbb0d227..5fcddbf53 100755
--- a/src/test/regress/bin/diff
+++ b/src/test/regress/bin/diff
@@ -18,7 +18,7 @@ file2="${@:(-1):1}"
 # filename of the expected file as the test name. We can have multiple
 # expected files for a single test with _0, _1, ... suffixes.
 # So for the test name, we also strip the additional suffix.
-test=$(basename $file1 .out | sed -E "s/_[0-9]+$//")
+test=$(basename "$file1" .out | sed -E "s/_[0-9]+$//")
 args=${@:1:$#-2}
 BASEDIR=$(dirname "$0")
 
@@ -33,16 +33,11 @@ fi
 if test -z "${VANILLATEST:-}"
 then
 	touch "$file1"  # when adding a new test the expected file does not exist
-	sed -Ef $BASEDIR/normalize.sed < $file1 > "$file1.modified"
-	mv "$file1" "$file1.unmodified"
-	mv "$file1.modified" "$file1"
+	sed -Ef $BASEDIR/normalize.sed < "$file1" > "$file1.modified"
 	sed -Ef $BASEDIR/normalize.sed < "$file2" > "$file2.modified"
-	mv "$file2" "$file2.unmodified"
-	mv "$file2.modified" "$file2"
-	$DIFF -w $args $file1 $file2
-	exitcode=$?
-	exit $exitcode
+	"$DIFF" -w $args "$file1.modified" "$file2.modified" | diff-filter
+	exit ${PIPESTATUS[0]}
 else
-	exec $DIFF -w $args $file1 $file2
+	exec "$DIFF" -w $args "$file1" "$file2"
 fi
 
diff --git a/src/test/regress/bin/diff-filter b/src/test/regress/bin/diff-filter
new file mode 100755
index 000000000..092dee629
--- /dev/null
+++ b/src/test/regress/bin/diff-filter
@@ -0,0 +1,39 @@
+#!/usr/bin/env python3
+
+"""
+diff-filter denormalizes diff output by having lines beginning with ' ' or '+'
+come from file2's unmodified version.
+"""
+
+def main():
+	from sys import stdin, stdout
+
+	for line in stdin:
+		if line.startswith('+++ '):
+			tab = line.rindex('\t')
+			fname = line[4:tab]
+			file2 = iter(open(fname.replace('.modified', '')))
+			file2line = 1
+			stdout.write(line)
+		elif line.startswith('@@ '):
+			idx_start = line.index('+') + 1
+			idx_end = idx_start + 1
+			while line[idx_end].isdigit():
+				idx_end += 1
+			linenum = int(line[idx_start:idx_end])
+			while file2line < linenum:
+				next(file2)
+				file2line += 1
+			stdout.write(line)
+		elif line.startswith(' '):
+			stdout.write(' ')
+			stdout.write(next(file2))
+			file2line += 1
+		elif line.startswith('+'):
+			stdout.write('+')
+			stdout.write(next(file2))
+			file2line += 1
+		else:
+			stdout.write(line)
+
+main()