From 3310dd1d197495fbfa2d7ee490e19e6d08e1d30f Mon Sep 17 00:00:00 2001
From: wxiaoguang <wxiaoguang@gmail.com>
Date: Sat, 23 Jul 2022 19:28:02 +0800
Subject: Improve code diff highlight, fix incorrect rendered diff result
 (#19958)

Use Unicode placeholders to replace HTML tags and HTML entities first, then do diff, then recover the HTML tags and HTML entities. Now the code diff with highlight has stable behavior, and won't emit broken tags.
---
 services/gitdiff/highlightdiff_test.go | 126 +++++++++++++++++++++++++++++++++
 1 file changed, 126 insertions(+)
 create mode 100644 services/gitdiff/highlightdiff_test.go

(limited to 'services/gitdiff/highlightdiff_test.go')

diff --git a/services/gitdiff/highlightdiff_test.go b/services/gitdiff/highlightdiff_test.go
new file mode 100644
index 0000000000..1cd78bc942
--- /dev/null
+++ b/services/gitdiff/highlightdiff_test.go
@@ -0,0 +1,126 @@
+// Copyright 2022 The Gitea Authors. All rights reserved.
+// Use of this source code is governed by a MIT-style
+// license that can be found in the LICENSE file.
+
+package gitdiff
+
+import (
+	"fmt"
+	"strings"
+	"testing"
+
+	"github.com/sergi/go-diff/diffmatchpatch"
+	"github.com/stretchr/testify/assert"
+)
+
+func TestDiffWithHighlight(t *testing.T) {
+	hcd := newHighlightCodeDiff()
+	diffs := hcd.diffWithHighlight(
+		"main.v", "",
+		"		run('<>')\n",
+		"		run(db)\n",
+	)
+
+	expected := `		<span class="n">run</span><span class="o">(</span><span class="removed-code"><span class="k">&#39;</span><span class="o">&lt;</span><span class="o">&gt;</span><span class="k">&#39;</span></span><span class="o">)</span>` + "\n"
+	output := diffToHTML(nil, diffs, DiffLineDel)
+	assert.Equal(t, expected, output)
+
+	expected = `		<span class="n">run</span><span class="o">(</span><span class="added-code"><span class="n">db</span></span><span class="o">)</span>` + "\n"
+	output = diffToHTML(nil, diffs, DiffLineAdd)
+	assert.Equal(t, expected, output)
+
+	hcd = newHighlightCodeDiff()
+	hcd.placeholderTokenMap['O'] = "<span>"
+	hcd.placeholderTokenMap['C'] = "</span>"
+	diff := diffmatchpatch.Diff{}
+
+	diff.Text = "OC"
+	hcd.recoverOneDiff(&diff)
+	assert.Equal(t, "<span></span>", diff.Text)
+
+	diff.Text = "O"
+	hcd.recoverOneDiff(&diff)
+	assert.Equal(t, "<span></span>", diff.Text)
+
+	diff.Text = "C"
+	hcd.recoverOneDiff(&diff)
+	assert.Equal(t, "", diff.Text)
+}
+
+func TestDiffWithHighlightPlaceholder(t *testing.T) {
+	hcd := newHighlightCodeDiff()
+	diffs := hcd.diffWithHighlight(
+		"main.js", "",
+		"a='\U00100000'",
+		"a='\U0010FFFD''",
+	)
+	assert.Equal(t, "", hcd.placeholderTokenMap[0x00100000])
+	assert.Equal(t, "", hcd.placeholderTokenMap[0x0010FFFD])
+
+	expected := fmt.Sprintf(`<span class="line"><span class="cl"><span class="nx">a</span><span class="o">=</span><span class="s1">&#39;</span><span class="removed-code">%s</span>&#39;</span></span>`, "\U00100000")
+	output := diffToHTML(hcd.lineWrapperTags, diffs, DiffLineDel)
+	assert.Equal(t, expected, output)
+
+	hcd = newHighlightCodeDiff()
+	diffs = hcd.diffWithHighlight(
+		"main.js", "",
+		"a='\U00100000'",
+		"a='\U0010FFFD'",
+	)
+	expected = fmt.Sprintf(`<span class="nx">a</span><span class="o">=</span><span class="s1">&#39;</span><span class="added-code">%s</span>&#39;`, "\U0010FFFD")
+	output = diffToHTML(nil, diffs, DiffLineAdd)
+	assert.Equal(t, expected, output)
+}
+
+func TestDiffWithHighlightPlaceholderExhausted(t *testing.T) {
+	hcd := newHighlightCodeDiff()
+	hcd.placeholderMaxCount = 0
+	diffs := hcd.diffWithHighlight(
+		"main.js", "",
+		"'",
+		``,
+	)
+	output := diffToHTML(nil, diffs, DiffLineDel)
+	expected := fmt.Sprintf(`<span class="removed-code">%s#39;</span>`, "\uFFFD")
+	assert.Equal(t, expected, output)
+
+	hcd = newHighlightCodeDiff()
+	hcd.placeholderMaxCount = 0
+	diffs = hcd.diffWithHighlight(
+		"main.js", "",
+		"a < b",
+		"a > b",
+	)
+	output = diffToHTML(nil, diffs, DiffLineDel)
+	expected = fmt.Sprintf(`a %s<span class="removed-code">l</span>t; b`, "\uFFFD")
+	assert.Equal(t, expected, output)
+
+	output = diffToHTML(nil, diffs, DiffLineAdd)
+	expected = fmt.Sprintf(`a %s<span class="added-code">g</span>t; b`, "\uFFFD")
+	assert.Equal(t, expected, output)
+}
+
+func TestDiffWithHighlightTagMatch(t *testing.T) {
+	totalOverflow := 0
+	for i := 0; i < 100; i++ {
+		hcd := newHighlightCodeDiff()
+		hcd.placeholderMaxCount = i
+		diffs := hcd.diffWithHighlight(
+			"main.js", "",
+			"a='1'",
+			"b='2'",
+		)
+		totalOverflow += hcd.placeholderOverflowCount
+
+		output := diffToHTML(nil, diffs, DiffLineDel)
+		c1 := strings.Count(output, "<span")
+		c2 := strings.Count(output, "</span")
+		assert.Equal(t, c1, c2)
+
+		output = diffToHTML(nil, diffs, DiffLineAdd)
+		c1 = strings.Count(output, "<span")
+		c2 = strings.Count(output, "</span")
+		assert.Equal(t, c1, c2)
+	}
+	assert.NotZero(t, totalOverflow)
+}
-- 
cgit v1.2.3