[v12.0/forgejo] fix(code-search): HighlightSearchResultCode should count the number of bytes and not the number of runes (#8498)

**Backport:** https://codeberg.org/forgejo/forgejo/pulls/8492

fixes incorrect handling of unicode in the matched line

Co-authored-by: Shiny Nematoda <snematoda.751k2@aleeas.com>
Reviewed-on: https://codeberg.org/forgejo/forgejo/pulls/8498
Co-authored-by: forgejo-backport-action <forgejo-backport-action@noreply.codeberg.org>
Co-committed-by: forgejo-backport-action <forgejo-backport-action@noreply.codeberg.org>

modules/indexer/code/search.go

@@ -97,7 +97,7 @@ func HighlightSearchResultCode(filename string, lineNums []int, highlightRanges
 	conv := hcd.ConvertToPlaceholders(string(hl))
 	convLines := strings.Split(conv, "\n")
 
-	// each highlightRange is of the form [line number, start pos, end pos]
+	// each highlightRange is of the form [line number, start byte offset, end byte offset]
 	for _, highlightRange := range highlightRanges {
 		ln, start, end := highlightRange[0], highlightRange[1], highlightRange[2]
 		line := convLines[ln]
@@ -105,13 +105,16 @@ func HighlightSearchResultCode(filename string, lineNums []int, highlightRanges
 			continue
 		}
 
+		sr := strings.NewReader(line)
 		sb := strings.Builder{}
 		count := -1
 		isOpen := false
-		for _, r := range line {
+		for r, size, err := sr.ReadRune(); err == nil; r, size, err = sr.ReadRune() {
 			if token, ok := hcd.PlaceholderTokenMap[r];
 			// token was not found
-			!ok ||
+			!ok {
+				count += size
+			} else if
 			// token was marked as used
 			token == "" ||
 				// the token is not an valid html tag emitted by chroma
@@ -132,15 +135,15 @@ func HighlightSearchResultCode(filename string, lineNums []int, highlightRanges
 				continue
 			}
 
-			switch count {
-			case end:
+			switch {
+			case count >= end:
 				// if tag is not open, no need to close
 				if !isOpen {
 					break
 				}
 				sb.WriteRune(endTag)
 				isOpen = false
-			case start:
+			case count >= start:
 				// if tag is open, do not open again
 				if isOpen {
 					break
@@ -161,7 +164,7 @@ func HighlightSearchResultCode(filename string, lineNums []int, highlightRanges
 	highlightedLines := strings.Split(hcd.Recover(conv), "\n")
 	// The lineNums outputted by highlight.Code might not match the original lineNums, because "highlight" removes the last `\n`
 	lines := make([]ResultLine, min(len(highlightedLines), len(lineNums)))
-	for i := 0; i < len(lines); i++ {
+	for i := range len(lines) {
 		lines[i].Num = lineNums[i]
 		lines[i].FormattedContent = template.HTML(highlightedLines[i])
 	}

modules/indexer/code/search_test.go

@@ -0,0 +1,122 @@
+// Copyright 2025 The Forgejo Authors. All rights reserved.
+// SPDX-License-Identifier: MIT
+
+package code
+
+import (
+	"html/template"
+	"strings"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+)
+
+func TestHighlightSearchResultCode(t *testing.T) {
+	opts := []struct {
+		Title  string
+		File   string
+		Lines  []int
+		Range  [][3]int
+		Code   string
+		Result []template.HTML
+	}{
+		{
+			Title: "One Match Text",
+			File:  "test.txt",
+			Range: [][3]int{{1, 5, 9}},
+			Code:  "First Line\nMark this only\nThe End",
+			Result: []template.HTML{
+				"First Line",
+				"Mark <span class=\"search-highlight\">this</span> only",
+				"The End",
+			},
+		},
+		{
+			Title: "Two Match Text",
+			File:  "test.txt",
+			Range: [][3]int{
+				{1, 5, 9},
+				{2, 5, 9},
+			},
+			Code: "First Line\nMark this only\nMark this too\nThe End",
+			Result: []template.HTML{
+				"First Line",
+				"Mark <span class=\"search-highlight\">this</span> only",
+				"Mark <span class=\"search-highlight\">this</span> too",
+				"The End",
+			},
+		},
+		{
+			Title: "Unicode Before",
+			File:  "test.txt",
+			Range: [][3]int{{1, 10, 14}},
+			Code:  "First Line\nMark 👉 this only\nThe End",
+			Result: []template.HTML{
+				"First Line",
+				"Mark 👉 <span class=\"search-highlight\">this</span> only",
+				"The End",
+			},
+		},
+		{
+			Title: "Unicode Between",
+			File:  "test.txt",
+			Range: [][3]int{{1, 5, 14}},
+			Code:  "First Line\nMark this 😊 only\nThe End",
+			Result: []template.HTML{
+				"First Line",
+				"Mark <span class=\"search-highlight\">this 😊</span> only",
+				"The End",
+			},
+		},
+		{
+			Title: "Unicode Before And Between",
+			File:  "test.txt",
+			Range: [][3]int{{1, 10, 19}},
+			Code:  "First Line\nMark 👉 this 😊 only\nThe End",
+			Result: []template.HTML{
+				"First Line",
+				"Mark 👉 <span class=\"search-highlight\">this 😊</span> only",
+				"The End",
+			},
+		},
+		{
+			Title: "Golang",
+			File:  "test.go",
+			Range: [][3]int{{1, 14, 23}},
+			Code:  "func main() {\n\tfmt.Println(\"mark this\")\n}",
+			Result: []template.HTML{
+				"<span class=\"kd\">func</span> <span class=\"nf\">main</span><span class=\"p\">(</span><span class=\"p\">)</span> <span class=\"p\">{</span>",
+				"\t<span class=\"nx\">fmt</span><span class=\"p\">.</span><span class=\"nf\">Println</span><span class=\"p\">(</span><span class=\"s\">&#34;<span class=\"search-highlight\">mark this</span>&#34;</span><span class=\"p\">)</span>",
+				"<span class=\"p\">}</span>",
+			},
+		},
+		{
+			Title: "Golang Unicode",
+			File:  "test.go",
+			Range: [][3]int{{1, 14, 28}},
+			Code:  "func main() {\n\tfmt.Println(\"mark this 😊\")\n}",
+			Result: []template.HTML{
+				"<span class=\"kd\">func</span> <span class=\"nf\">main</span><span class=\"p\">(</span><span class=\"p\">)</span> <span class=\"p\">{</span>",
+				"\t<span class=\"nx\">fmt</span><span class=\"p\">.</span><span class=\"nf\">Println</span><span class=\"p\">(</span><span class=\"s\">&#34;<span class=\"search-highlight\">mark this 😊</span>&#34;</span><span class=\"p\">)</span>",
+				"<span class=\"p\">}</span>",
+			},
+		},
+	}
+	for _, o := range opts {
+		t.Run(o.Title, func(t *testing.T) {
+			lines := []int{}
+			for i := range strings.Count(strings.TrimSuffix(o.Code, "\n"), "\n") + 1 {
+				lines = append(lines, i+1)
+			}
+			res := HighlightSearchResultCode(o.File, lines, o.Range, o.Code)
+			assert.Len(t, res, len(o.Result))
+			assert.Len(t, res, len(lines))
+
+			for i, r := range res {
+				require.Equal(t, lines[i], r.Num)
+				require.Equal(t, o.Result[i], r.FormattedContent)
+			}
+		})
+	}
+}