Make Markdown fenced code block work with more syntaxes (#37154)

modules/markup/markdown/goldmark.go

@@ -70,6 +70,8 @@ func (g *ASTTransformer) Transform(node *ast.Document, reader text.Reader, pc pa
 			}
 		case *ast.CodeSpan:
 			g.transformCodeSpan(ctx, v, reader)
+		case *ast.FencedCodeBlock:
+			g.transformFencedCodeblock(v, reader)
 		case *ast.Blockquote:
 			return g.transformBlockquote(v, reader)
 		}

modules/markup/markdown/markdown_test.go

@@ -600,3 +600,22 @@ func TestMarkdownUlDir(t *testing.T) {
 </ul>
 `, string(result))
 }
+
+func TestMarkdownFencedCodeBlock(t *testing.T) {
+	testRender := func(input, expected string) {
+		buffer, err := markdown.RenderString(markup.NewTestRenderContext(), input)
+		assert.NoError(t, err)
+		assert.Equal(t, strings.TrimSpace(expected), strings.TrimSpace(string(buffer)))
+	}
+	const nl = "\n"
+	const prefix = `<div class="code-block-container code-overflow-scroll"><pre class="code-block">`
+	const suffix = `</pre></div>`
+
+	testRender("```\ncode\n```", prefix+`<code class="chroma language-text display">code`+nl+`</code>`+suffix)
+
+	const jsCommon = prefix + `<code class="chroma language-js display"><span class="nx">code</span>` + nl + `</code>` + suffix
+	testRender("```js\ncode\n```", jsCommon)
+	testRender("```js:app.ts\ncode\n```", jsCommon)
+	testRender("```js,ignore\ncode\n```", jsCommon)
+	testRender("```js ignore\ncode\n```", jsCommon)
+}

modules/markup/markdown/transform_codeblock.go

@@ -0,0 +1,32 @@
+// Copyright 2026 The Gitea Authors. All rights reserved.
+// SPDX-License-Identifier: MIT
+
+package markdown
+
+import (
+	"github.com/yuin/goldmark/ast"
+	"github.com/yuin/goldmark/text"
+)
+
+func (g *ASTTransformer) transformFencedCodeblock(v *ast.FencedCodeBlock, reader text.Reader) {
+	// * Some engines support a meta syntax for appending the filename after the language, separated by a colon
+	//   * https://www.glukhov.org/documentation-tools/markdown/markdown-codeblocks/
+	// * Some engines support additional "options" after the language, separated by a space or comma: ```rust,ignore```
+	//   * https://docs.readme.com/rdmd/docs/code-blocks
+	//   * https://next-book.vercel.app/reference/fencedcode
+	if v.Info == nil {
+		return
+	}
+	info := v.Info.Segment.Value(reader.Source())
+	newEnd := -1
+	for i, b := range info {
+		if b == ' ' || b == ',' || b == ':' {
+			newEnd = i
+			break
+		}
+	}
+	if newEnd != -1 {
+		start := v.Info.Segment.Start
+		v.Info = ast.NewTextSegment(text.NewSegment(start, start+newEnd))
+	}
+}