From 1cec1cf33df504d1071bc9f2325e18319f8209c4 Mon Sep 17 00:00:00 2001
From: Robert <43223+rspier@users.noreply.github.com>
Date: Tue, 10 Dec 2024 11:43:11 -0800
Subject: [PATCH] Fix potential tsan race

When run under TSan, a data race (https://go.dev/doc/articles/race_detector) is detected on the append of bestCommonA and B.  They're never used independently, always concatenated, so replace them with a single bestCommon.
---
 diffmatchpatch/diff.go | 10 ++++------
 1 file changed, 4 insertions(+), 6 deletions(-)

diff --git a/diffmatchpatch/diff.go b/diffmatchpatch/diff.go
index 915d509..9352eec 100644
--- a/diffmatchpatch/diff.go
+++ b/diffmatchpatch/diff.go
@@ -563,8 +563,7 @@ func (dmp *DiffMatchPatch) diffHalfMatch(text1, text2 []rune) [][]rune {
 // diffHalfMatchI checks if a substring of shorttext exist within longtext such that the substring is at least half the length of longtext?
 // Returns a slice containing the prefix of longtext, the suffix of longtext, the prefix of shorttext, the suffix of shorttext and the common middle, or null if there was no match.
 func (dmp *DiffMatchPatch) diffHalfMatchI(l, s []rune, i int) [][]rune {
-	var bestCommonA []rune
-	var bestCommonB []rune
+	var bestCommon []rune
 	var bestCommonLen int
 	var bestLongtextA []rune
 	var bestLongtextB []rune
@@ -579,9 +578,8 @@ func (dmp *DiffMatchPatch) diffHalfMatchI(l, s []rune, i int) [][]rune {
 		suffixLength := commonSuffixLength(l[:i], s[:j])
 
 		if bestCommonLen < suffixLength+prefixLength {
-			bestCommonA = s[j-suffixLength : j]
-			bestCommonB = s[j : j+prefixLength]
-			bestCommonLen = len(bestCommonA) + len(bestCommonB)
+			bestCommon = s[j-suffixLength : j+prefixLength]
+			bestCommonLen = len(bestCommon)
 			bestLongtextA = l[:i-suffixLength]
 			bestLongtextB = l[i+prefixLength:]
 			bestShorttextA = s[:j-suffixLength]
@@ -598,7 +596,7 @@ func (dmp *DiffMatchPatch) diffHalfMatchI(l, s []rune, i int) [][]rune {
 		bestLongtextB,
 		bestShorttextA,
 		bestShorttextB,
-		append(bestCommonA, bestCommonB...),
+		bestCommon,
 	}
 }