Refactor markdown render (#30139)

Only split the file into small ones (and rename AttentionTypes to
attentionTypes)

8 files changed, 364 insertions, 257 deletions

diff --git a/modules/markup/markdown/goldmark.go b/modules/markup/markdown/goldmark.go
index b61299c480..b8b3aeaab0 100644
--- a/modules/markup/markdown/goldmark.go
+++ b/modules/markup/markdown/goldmark.go
@@ -4,19 +4,14 @@
 package markdown
 
 import (
-	"bytes"
 	"fmt"
 	"regexp"
 	"strings"
 
 	"code.gitea.io/gitea/modules/container"
 	"code.gitea.io/gitea/modules/markup"
-	"code.gitea.io/gitea/modules/markup/common"
 	"code.gitea.io/gitea/modules/setting"
-	"code.gitea.io/gitea/modules/svg"
-	giteautil "code.gitea.io/gitea/modules/util"
 
-	"github.com/microcosm-cc/bluemonday/css"
 	"github.com/yuin/goldmark/ast"
 	east "github.com/yuin/goldmark/extension/ast"
 	"github.com/yuin/goldmark/parser"
@@ -28,12 +23,12 @@ import (
 
 // ASTTransformer is a default transformer of the goldmark tree.
 type ASTTransformer struct {
-	AttentionTypes container.Set[string]
+	attentionTypes container.Set[string]
 }
 
 func NewASTTransformer() *ASTTransformer {
 	return &ASTTransformer{
-		AttentionTypes: container.SetOf("note", "tip", "important", "warning", "caution"),
+		attentionTypes: container.SetOf("note", "tip", "important", "warning", "caution"),
 	}
 }
 
@@ -66,123 +61,15 @@ func (g *ASTTransformer) Transform(node *ast.Document, reader text.Reader, pc pa
 
 		switch v := n.(type) {
 		case *ast.Heading:
-			for _, attr := range v.Attributes() {
-				if _, ok := attr.Value.([]byte); !ok {
-					v.SetAttribute(attr.Name, []byte(fmt.Sprintf("%v", attr.Value)))
-				}
-			}
-			txt := n.Text(reader.Source())
-			header := markup.Header{
-				Text:  util.BytesToReadOnlyString(txt),
-				Level: v.Level,
-			}
-			if id, found := v.AttributeString("id"); found {
-				header.ID = util.BytesToReadOnlyString(id.([]byte))
-			}
-			tocList = append(tocList, header)
-			g.applyElementDir(v)
+			g.transformHeading(ctx, v, reader, &tocList)
 		case *ast.Paragraph:
 			g.applyElementDir(v)
 		case *ast.Image:
-			// Images need two things:
-			//
-			// 1. Their src needs to munged to be a real value
-			// 2. If they're not wrapped with a link they need a link wrapper
-
-			// Check if the destination is a real link
-			if len(v.Destination) > 0 && !markup.IsFullURLBytes(v.Destination) {
-				v.Destination = []byte(giteautil.URLJoin(
-					ctx.Links.ResolveMediaLink(ctx.IsWiki),
-					strings.TrimLeft(string(v.Destination), "/"),
-				))
-			}
-
-			parent := n.Parent()
-			// Create a link around image only if parent is not already a link
-			if _, ok := parent.(*ast.Link); !ok && parent != nil {
-				next := n.NextSibling()
-
-				// Create a link wrapper
-				wrap := ast.NewLink()
-				wrap.Destination = v.Destination
-				wrap.Title = v.Title
-				wrap.SetAttributeString("target", []byte("_blank"))
-
-				// Duplicate the current image node
-				image := ast.NewImage(ast.NewLink())
-				image.Destination = v.Destination
-				image.Title = v.Title
-				for _, attr := range v.Attributes() {
-					image.SetAttribute(attr.Name, attr.Value)
-				}
-				for child := v.FirstChild(); child != nil; {
-					next := child.NextSibling()
-					image.AppendChild(image, child)
-					child = next
-				}
-
-				// Append our duplicate image to the wrapper link
-				wrap.AppendChild(wrap, image)
-
-				// Wire in the next sibling
-				wrap.SetNextSibling(next)
-
-				// Replace the current node with the wrapper link
-				parent.ReplaceChild(parent, n, wrap)
-
-				// But most importantly ensure the next sibling is still on the old image too
-				v.SetNextSibling(next)
-			}
+			g.transformImage(ctx, v, reader)
 		case *ast.Link:
-			// Links need their href to munged to be a real value
-			link := v.Destination
-			isAnchorFragment := len(link) > 0 && link[0] == '#'
-			if !isAnchorFragment && !markup.IsFullURLBytes(link) {
-				base := ctx.Links.Base
-				if ctx.IsWiki {
-					base = ctx.Links.WikiLink()
-				} else if ctx.Links.HasBranchInfo() {
-					base = ctx.Links.SrcLink()
-				}
-				link = []byte(giteautil.URLJoin(base, string(link)))
-			}
-			if isAnchorFragment {
-				link = []byte("#user-content-" + string(link)[1:])
-			}
-			v.Destination = link
+			g.transformLink(ctx, v, reader)
 		case *ast.List:
-			if v.HasChildren() {
-				children := make([]ast.Node, 0, v.ChildCount())
-				child := v.FirstChild()
-				for child != nil {
-					children = append(children, child)
-					child = child.NextSibling()
-				}
-				v.RemoveChildren(v)
-
-				for _, child := range children {
-					listItem := child.(*ast.ListItem)
-					if !child.HasChildren() || !child.FirstChild().HasChildren() {
-						v.AppendChild(v, child)
-						continue
-					}
-					taskCheckBox, ok := child.FirstChild().FirstChild().(*east.TaskCheckBox)
-					if !ok {
-						v.AppendChild(v, child)
-						continue
-					}
-					newChild := NewTaskCheckBoxListItem(listItem)
-					newChild.IsChecked = taskCheckBox.IsChecked
-					newChild.SetAttributeString("class", []byte("task-list-item"))
-					segments := newChild.FirstChild().Lines()
-					if segments.Len() > 0 {
-						segment := segments.At(0)
-						newChild.SourcePosition = rc.metaLength + segment.Start
-					}
-					v.AppendChild(v, newChild)
-				}
-			}
-			g.applyElementDir(v)
+			g.transformList(ctx, v, reader, rc)
 		case *ast.Text:
 			if v.SoftLineBreak() && !v.HardLineBreak() {
 				if ctx.Metas["mode"] != "document" {
@@ -192,10 +79,7 @@ func (g *ASTTransformer) Transform(node *ast.Document, reader text.Reader, pc pa
 				}
 			}
 		case *ast.CodeSpan:
-			colorContent := n.Text(reader.Source())
-			if css.ColorHandler(strings.ToLower(string(colorContent))) {
-				v.AppendChild(v, NewColorPreview(colorContent))
-			}
+			g.transformCodeSpan(ctx, v, reader)
 		case *ast.Blockquote:
 			return g.transformBlockquote(v, reader)
 		}
@@ -219,50 +103,6 @@ func (g *ASTTransformer) Transform(node *ast.Document, reader text.Reader, pc pa
 	}
 }
 
-type prefixedIDs struct {
-	values container.Set[string]
-}
-
-// Generate generates a new element id.
-func (p *prefixedIDs) Generate(value []byte, kind ast.NodeKind) []byte {
-	dft := []byte("id")
-	if kind == ast.KindHeading {
-		dft = []byte("heading")
-	}
-	return p.GenerateWithDefault(value, dft)
-}
-
-// GenerateWithDefault generates a new element id.
-func (p *prefixedIDs) GenerateWithDefault(value, dft []byte) []byte {
-	result := common.CleanValue(value)
-	if len(result) == 0 {
-		result = dft
-	}
-	if !bytes.HasPrefix(result, []byte("user-content-")) {
-		result = append([]byte("user-content-"), result...)
-	}
-	if p.values.Add(util.BytesToReadOnlyString(result)) {
-		return result
-	}
-	for i := 1; ; i++ {
-		newResult := fmt.Sprintf("%s-%d", result, i)
-		if p.values.Add(newResult) {
-			return []byte(newResult)
-		}
-	}
-}
-
-// Put puts a given element id to the used ids table.
-func (p *prefixedIDs) Put(value []byte) {
-	p.values.Add(util.BytesToReadOnlyString(value))
-}
-
-func newPrefixedIDs() *prefixedIDs {
-	return &prefixedIDs{
-		values: make(container.Set[string]),
-	}
-}
-
 // NewHTMLRenderer creates a HTMLRenderer to render
 // in the gitea form.
 func NewHTMLRenderer(opts ...html.Option) renderer.NodeRenderer {
@@ -295,60 +135,6 @@ func (r *HTMLRenderer) RegisterFuncs(reg renderer.NodeRendererFuncRegisterer) {
 	reg.Register(east.KindTaskCheckBox, r.renderTaskCheckBox)
 }
 
-// renderCodeSpan renders CodeSpan elements (like goldmark upstream does) but also renders ColorPreview elements.
-// See #21474 for reference
-func (r *HTMLRenderer) renderCodeSpan(w util.BufWriter, source []byte, n ast.Node, entering bool) (ast.WalkStatus, error) {
-	if entering {
-		if n.Attributes() != nil {
-			_, _ = w.WriteString("<code")
-			html.RenderAttributes(w, n, html.CodeAttributeFilter)
-			_ = w.WriteByte('>')
-		} else {
-			_, _ = w.WriteString("<code>")
-		}
-		for c := n.FirstChild(); c != nil; c = c.NextSibling() {
-			switch v := c.(type) {
-			case *ast.Text:
-				segment := v.Segment
-				value := segment.Value(source)
-				if bytes.HasSuffix(value, []byte("\n")) {
-					r.Writer.RawWrite(w, value[:len(value)-1])
-					r.Writer.RawWrite(w, []byte(" "))
-				} else {
-					r.Writer.RawWrite(w, value)
-				}
-			case *ColorPreview:
-				_, _ = w.WriteString(fmt.Sprintf(`<span class="color-preview" style="background-color: %v"></span>`, string(v.Color)))
-			}
-		}
-		return ast.WalkSkipChildren, nil
-	}
-	_, _ = w.WriteString("</code>")
-	return ast.WalkContinue, nil
-}
-
-// renderAttention renders a quote marked with i.e. "> **Note**" or "> **Warning**" with a corresponding svg
-func (r *HTMLRenderer) renderAttention(w util.BufWriter, source []byte, node ast.Node, entering bool) (ast.WalkStatus, error) {
-	if entering {
-		n := node.(*Attention)
-		var octiconName string
-		switch n.AttentionType {
-		case "tip":
-			octiconName = "light-bulb"
-		case "important":
-			octiconName = "report"
-		case "warning":
-			octiconName = "alert"
-		case "caution":
-			octiconName = "stop"
-		default: // including "note"
-			octiconName = "info"
-		}
-		_, _ = w.WriteString(string(svg.RenderHTML("octicon-"+octiconName, 16, "attention-icon attention-"+n.AttentionType)))
-	}
-	return ast.WalkContinue, nil
-}
-
 func (r *HTMLRenderer) renderDocument(w util.BufWriter, source []byte, node ast.Node, entering bool) (ast.WalkStatus, error) {
 	n := node.(*ast.Document)
 
@@ -435,38 +221,3 @@ func (r *HTMLRenderer) renderIcon(w util.BufWriter, source []byte, node ast.Node
 
 	return ast.WalkContinue, nil
 }
-
-func (r *HTMLRenderer) renderTaskCheckBoxListItem(w util.BufWriter, source []byte, node ast.Node, entering bool) (ast.WalkStatus, error) {
-	n := node.(*TaskCheckBoxListItem)
-	if entering {
-		if n.Attributes() != nil {
-			_, _ = w.WriteString("<li")
-			html.RenderAttributes(w, n, html.ListItemAttributeFilter)
-			_ = w.WriteByte('>')
-		} else {
-			_, _ = w.WriteString("<li>")
-		}
-		fmt.Fprintf(w, `<input type="checkbox" disabled="" data-source-position="%d"`, n.SourcePosition)
-		if n.IsChecked {
-			_, _ = w.WriteString(` checked=""`)
-		}
-		if r.XHTML {
-			_, _ = w.WriteString(` />`)
-		} else {
-			_ = w.WriteByte('>')
-		}
-		fc := n.FirstChild()
-		if fc != nil {
-			if _, ok := fc.(*ast.TextBlock); !ok {
-				_ = w.WriteByte('\n')
-			}
-		}
-	} else {
-		_, _ = w.WriteString("</li>\n")
-	}
-	return ast.WalkContinue, nil
-}
-
-func (r *HTMLRenderer) renderTaskCheckBox(w util.BufWriter, source []byte, node ast.Node, entering bool) (ast.WalkStatus, error) {
-	return ast.WalkContinue, nil
-}
diff --git a/modules/markup/markdown/prefixed_id.go b/modules/markup/markdown/prefixed_id.go
new file mode 100644
index 0000000000..9c60949202
--- /dev/null
+++ b/modules/markup/markdown/prefixed_id.go
@@ -0,0 +1,59 @@
+// Copyright 2024 The Gitea Authors. All rights reserved.
+// SPDX-License-Identifier: MIT
+
+package markdown
+
+import (
+	"bytes"
+	"fmt"
+
+	"code.gitea.io/gitea/modules/container"
+	"code.gitea.io/gitea/modules/markup/common"
+
+	"github.com/yuin/goldmark/ast"
+	"github.com/yuin/goldmark/util"
+)
+
+type prefixedIDs struct {
+	values container.Set[string]
+}
+
+// Generate generates a new element id.
+func (p *prefixedIDs) Generate(value []byte, kind ast.NodeKind) []byte {
+	dft := []byte("id")
+	if kind == ast.KindHeading {
+		dft = []byte("heading")
+	}
+	return p.GenerateWithDefault(value, dft)
+}
+
+// GenerateWithDefault generates a new element id.
+func (p *prefixedIDs) GenerateWithDefault(value, dft []byte) []byte {
+	result := common.CleanValue(value)
+	if len(result) == 0 {
+		result = dft
+	}
+	if !bytes.HasPrefix(result, []byte("user-content-")) {
+		result = append([]byte("user-content-"), result...)
+	}
+	if p.values.Add(util.BytesToReadOnlyString(result)) {
+		return result
+	}
+	for i := 1; ; i++ {
+		newResult := fmt.Sprintf("%s-%d", result, i)
+		if p.values.Add(newResult) {
+			return []byte(newResult)
+		}
+	}
+}
+
+// Put puts a given element id to the used ids table.
+func (p *prefixedIDs) Put(value []byte) {
+	p.values.Add(util.BytesToReadOnlyString(value))
+}
+
+func newPrefixedIDs() *prefixedIDs {
+	return &prefixedIDs{
+		values: make(container.Set[string]),
+	}
+}
diff --git a/modules/markup/markdown/transform_blockquote.go b/modules/markup/markdown/transform_blockquote.go
index 65b735e83b..933f0e5c59 100644
--- a/modules/markup/markdown/transform_blockquote.go
+++ b/modules/markup/markdown/transform_blockquote.go
@@ -6,12 +6,37 @@ package markdown
 import (
 	"strings"
 
+	"code.gitea.io/gitea/modules/svg"
+
 	"github.com/yuin/goldmark/ast"
 	"github.com/yuin/goldmark/text"
+	"github.com/yuin/goldmark/util"
 	"golang.org/x/text/cases"
 	"golang.org/x/text/language"
 )
 
+// renderAttention renders a quote marked with i.e. "> **Note**" or "> **Warning**" with a corresponding svg
+func (r *HTMLRenderer) renderAttention(w util.BufWriter, source []byte, node ast.Node, entering bool) (ast.WalkStatus, error) {
+	if entering {
+		n := node.(*Attention)
+		var octiconName string
+		switch n.AttentionType {
+		case "tip":
+			octiconName = "light-bulb"
+		case "important":
+			octiconName = "report"
+		case "warning":
+			octiconName = "alert"
+		case "caution":
+			octiconName = "stop"
+		default: // including "note"
+			octiconName = "info"
+		}
+		_, _ = w.WriteString(string(svg.RenderHTML("octicon-"+octiconName, 16, "attention-icon attention-"+n.AttentionType)))
+	}
+	return ast.WalkContinue, nil
+}
+
 func (g *ASTTransformer) transformBlockquote(v *ast.Blockquote, reader text.Reader) (ast.WalkStatus, error) {
 	// We only want attention blockquotes when the AST looks like:
 	// > Text("[") Text("!TYPE") Text("]")
@@ -43,7 +68,7 @@ func (g *ASTTransformer) transformBlockquote(v *ast.Blockquote, reader text.Read
 
 	// grab attention type from markdown source
 	attentionType := strings.ToLower(val2[1:])
-	if !g.AttentionTypes.Contains(attentionType) {
+	if !g.attentionTypes.Contains(attentionType) {
 		return ast.WalkContinue, nil
 	}
 
diff --git a/modules/markup/markdown/transform_codespan.go b/modules/markup/markdown/transform_codespan.go
new file mode 100644
index 0000000000..bfff2897b0
--- /dev/null
+++ b/modules/markup/markdown/transform_codespan.go
@@ -0,0 +1,57 @@
+// Copyright 2024 The Gitea Authors. All rights reserved.
+// SPDX-License-Identifier: MIT
+
+package markdown
+
+import (
+	"bytes"
+	"fmt"
+	"strings"
+
+	"code.gitea.io/gitea/modules/markup"
+
+	"github.com/microcosm-cc/bluemonday/css"
+	"github.com/yuin/goldmark/ast"
+	"github.com/yuin/goldmark/renderer/html"
+	"github.com/yuin/goldmark/text"
+	"github.com/yuin/goldmark/util"
+)
+
+// renderCodeSpan renders CodeSpan elements (like goldmark upstream does) but also renders ColorPreview elements.
+// See #21474 for reference
+func (r *HTMLRenderer) renderCodeSpan(w util.BufWriter, source []byte, n ast.Node, entering bool) (ast.WalkStatus, error) {
+	if entering {
+		if n.Attributes() != nil {
+			_, _ = w.WriteString("<code")
+			html.RenderAttributes(w, n, html.CodeAttributeFilter)
+			_ = w.WriteByte('>')
+		} else {
+			_, _ = w.WriteString("<code>")
+		}
+		for c := n.FirstChild(); c != nil; c = c.NextSibling() {
+			switch v := c.(type) {
+			case *ast.Text:
+				segment := v.Segment
+				value := segment.Value(source)
+				if bytes.HasSuffix(value, []byte("\n")) {
+					r.Writer.RawWrite(w, value[:len(value)-1])
+					r.Writer.RawWrite(w, []byte(" "))
+				} else {
+					r.Writer.RawWrite(w, value)
+				}
+			case *ColorPreview:
+				_, _ = w.WriteString(fmt.Sprintf(`<span class="color-preview" style="background-color: %v"></span>`, string(v.Color)))
+			}
+		}
+		return ast.WalkSkipChildren, nil
+	}
+	_, _ = w.WriteString("</code>")
+	return ast.WalkContinue, nil
+}
+
+func (g *ASTTransformer) transformCodeSpan(ctx *markup.RenderContext, v *ast.CodeSpan, reader text.Reader) {
+	colorContent := v.Text(reader.Source())
+	if css.ColorHandler(strings.ToLower(string(colorContent))) {
+		v.AppendChild(v, NewColorPreview(colorContent))
+	}
+}
diff --git a/modules/markup/markdown/transform_heading.go b/modules/markup/markdown/transform_heading.go
new file mode 100644
index 0000000000..ce585a37de
--- /dev/null
+++ b/modules/markup/markdown/transform_heading.go
@@ -0,0 +1,32 @@
+// Copyright 2024 The Gitea Authors. All rights reserved.
+// SPDX-License-Identifier: MIT
+
+package markdown
+
+import (
+	"fmt"
+
+	"code.gitea.io/gitea/modules/markup"
+
+	"github.com/yuin/goldmark/ast"
+	"github.com/yuin/goldmark/text"
+	"github.com/yuin/goldmark/util"
+)
+
+func (g *ASTTransformer) transformHeading(ctx *markup.RenderContext, v *ast.Heading, reader text.Reader, tocList *[]markup.Header) {
+	for _, attr := range v.Attributes() {
+		if _, ok := attr.Value.([]byte); !ok {
+			v.SetAttribute(attr.Name, []byte(fmt.Sprintf("%v", attr.Value)))
+		}
+	}
+	txt := v.Text(reader.Source())
+	header := markup.Header{
+		Text:  util.BytesToReadOnlyString(txt),
+		Level: v.Level,
+	}
+	if id, found := v.AttributeString("id"); found {
+		header.ID = util.BytesToReadOnlyString(id.([]byte))
+	}
+	*tocList = append(*tocList, header)
+	g.applyElementDir(v)
+}
diff --git a/modules/markup/markdown/transform_image.go b/modules/markup/markdown/transform_image.go
new file mode 100644
index 0000000000..f290dc3721
--- /dev/null
+++ b/modules/markup/markdown/transform_image.go
@@ -0,0 +1,66 @@
+// Copyright 2024 The Gitea Authors. All rights reserved.
+// SPDX-License-Identifier: MIT
+
+package markdown
+
+import (
+	"strings"
+
+	"code.gitea.io/gitea/modules/markup"
+	giteautil "code.gitea.io/gitea/modules/util"
+
+	"github.com/yuin/goldmark/ast"
+	"github.com/yuin/goldmark/text"
+)
+
+func (g *ASTTransformer) transformImage(ctx *markup.RenderContext, v *ast.Image, reader text.Reader) {
+	// Images need two things:
+	//
+	// 1. Their src needs to munged to be a real value
+	// 2. If they're not wrapped with a link they need a link wrapper
+
+	// Check if the destination is a real link
+	if len(v.Destination) > 0 && !markup.IsFullURLBytes(v.Destination) {
+		v.Destination = []byte(giteautil.URLJoin(
+			ctx.Links.ResolveMediaLink(ctx.IsWiki),
+			strings.TrimLeft(string(v.Destination), "/"),
+		))
+	}
+
+	parent := v.Parent()
+	// Create a link around image only if parent is not already a link
+	if _, ok := parent.(*ast.Link); !ok && parent != nil {
+		next := v.NextSibling()
+
+		// Create a link wrapper
+		wrap := ast.NewLink()
+		wrap.Destination = v.Destination
+		wrap.Title = v.Title
+		wrap.SetAttributeString("target", []byte("_blank"))
+
+		// Duplicate the current image node
+		image := ast.NewImage(ast.NewLink())
+		image.Destination = v.Destination
+		image.Title = v.Title
+		for _, attr := range v.Attributes() {
+			image.SetAttribute(attr.Name, attr.Value)
+		}
+		for child := v.FirstChild(); child != nil; {
+			next := child.NextSibling()
+			image.AppendChild(image, child)
+			child = next
+		}
+
+		// Append our duplicate image to the wrapper link
+		wrap.AppendChild(wrap, image)
+
+		// Wire in the next sibling
+		wrap.SetNextSibling(next)
+
+		// Replace the current node with the wrapper link
+		parent.ReplaceChild(parent, v, wrap)
+
+		// But most importantly ensure the next sibling is still on the old image too
+		v.SetNextSibling(next)
+	}
+}
diff --git a/modules/markup/markdown/transform_link.go b/modules/markup/markdown/transform_link.go
new file mode 100644
index 0000000000..8bf19ea4ce
--- /dev/null
+++ b/modules/markup/markdown/transform_link.go
@@ -0,0 +1,31 @@
+// Copyright 2024 The Gitea Authors. All rights reserved.
+// SPDX-License-Identifier: MIT
+
+package markdown
+
+import (
+	"code.gitea.io/gitea/modules/markup"
+	giteautil "code.gitea.io/gitea/modules/util"
+
+	"github.com/yuin/goldmark/ast"
+	"github.com/yuin/goldmark/text"
+)
+
+func (g *ASTTransformer) transformLink(ctx *markup.RenderContext, v *ast.Link, reader text.Reader) {
+	// Links need their href to munged to be a real value
+	link := v.Destination
+	isAnchorFragment := len(link) > 0 && link[0] == '#'
+	if !isAnchorFragment && !markup.IsFullURLBytes(link) {
+		base := ctx.Links.Base
+		if ctx.IsWiki {
+			base = ctx.Links.WikiLink()
+		} else if ctx.Links.HasBranchInfo() {
+			base = ctx.Links.SrcLink()
+		}
+		link = []byte(giteautil.URLJoin(base, string(link)))
+	}
+	if isAnchorFragment {
+		link = []byte("#user-content-" + string(link)[1:])
+	}
+	v.Destination = link
+}
diff --git a/modules/markup/markdown/transform_list.go b/modules/markup/markdown/transform_list.go
new file mode 100644
index 0000000000..6563e2dd64
--- /dev/null
+++ b/modules/markup/markdown/transform_list.go
@@ -0,0 +1,86 @@
+// Copyright 2024 The Gitea Authors. All rights reserved.
+// SPDX-License-Identifier: MIT
+
+package markdown
+
+import (
+	"fmt"
+
+	"code.gitea.io/gitea/modules/markup"
+
+	"github.com/yuin/goldmark/ast"
+	east "github.com/yuin/goldmark/extension/ast"
+	"github.com/yuin/goldmark/renderer/html"
+	"github.com/yuin/goldmark/text"
+	"github.com/yuin/goldmark/util"
+)
+
+func (r *HTMLRenderer) renderTaskCheckBoxListItem(w util.BufWriter, source []byte, node ast.Node, entering bool) (ast.WalkStatus, error) {
+	n := node.(*TaskCheckBoxListItem)
+	if entering {
+		if n.Attributes() != nil {
+			_, _ = w.WriteString("<li")
+			html.RenderAttributes(w, n, html.ListItemAttributeFilter)
+			_ = w.WriteByte('>')
+		} else {
+			_, _ = w.WriteString("<li>")
+		}
+		fmt.Fprintf(w, `<input type="checkbox" disabled="" data-source-position="%d"`, n.SourcePosition)
+		if n.IsChecked {
+			_, _ = w.WriteString(` checked=""`)
+		}
+		if r.XHTML {
+			_, _ = w.WriteString(` />`)
+		} else {
+			_ = w.WriteByte('>')
+		}
+		fc := n.FirstChild()
+		if fc != nil {
+			if _, ok := fc.(*ast.TextBlock); !ok {
+				_ = w.WriteByte('\n')
+			}
+		}
+	} else {
+		_, _ = w.WriteString("</li>\n")
+	}
+	return ast.WalkContinue, nil
+}
+
+func (r *HTMLRenderer) renderTaskCheckBox(w util.BufWriter, source []byte, node ast.Node, entering bool) (ast.WalkStatus, error) {
+	return ast.WalkContinue, nil
+}
+
+func (g *ASTTransformer) transformList(ctx *markup.RenderContext, v *ast.List, reader text.Reader, rc *RenderConfig) {
+	if v.HasChildren() {
+		children := make([]ast.Node, 0, v.ChildCount())
+		child := v.FirstChild()
+		for child != nil {
+			children = append(children, child)
+			child = child.NextSibling()
+		}
+		v.RemoveChildren(v)
+
+		for _, child := range children {
+			listItem := child.(*ast.ListItem)
+			if !child.HasChildren() || !child.FirstChild().HasChildren() {
+				v.AppendChild(v, child)
+				continue
+			}
+			taskCheckBox, ok := child.FirstChild().FirstChild().(*east.TaskCheckBox)
+			if !ok {
+				v.AppendChild(v, child)
+				continue
+			}
+			newChild := NewTaskCheckBoxListItem(listItem)
+			newChild.IsChecked = taskCheckBox.IsChecked
+			newChild.SetAttributeString("class", []byte("task-list-item"))
+			segments := newChild.FirstChild().Lines()
+			if segments.Len() > 0 {
+				segment := segments.At(0)
+				newChild.SourcePosition = rc.metaLength + segment.Start
+			}
+			v.AppendChild(v, newChild)
+		}
+	}
+	g.applyElementDir(v)
+}