modules/markup: Lift out the GitHub callout transformer

This lifts out the GitHub callout transformer from
`modules/markup/markdown/goldmark.go` to `callout/github.go`.

While there, clean up the transformer code:

- Use a map to look up supported callout types, rather than a regexp.
- Allow the callout type to be in any case, rather than just uppercase.
- Simplified `.Segment.Value()` to `.Text()`.

Signed-off-by: Gergely Nagy <forgejo@gergo.csillger.hu>

modules/markup/markdown/ast.go

@@ -181,32 +181,3 @@ func IsColorPreview(node ast.Node) bool {
 	_, ok := node.(*ColorPreview)
 	return ok
 }
-
-// Attention is an inline for an attention
-type Attention struct {
-	ast.BaseInline
-	AttentionType string
-}
-
-// Dump implements Node.Dump.
-func (n *Attention) Dump(source []byte, level int) {
-	m := map[string]string{}
-	m["AttentionType"] = n.AttentionType
-	ast.DumpHelper(n, source, level, m, nil)
-}
-
-// KindAttention is the NodeKind for Attention
-var KindAttention = ast.NewNodeKind("Attention")
-
-// Kind implements Node.Kind.
-func (n *Attention) Kind() ast.NodeKind {
-	return KindAttention
-}
-
-// NewAttention returns a new Attention node.
-func NewAttention(attentionType string) *Attention {
-	return &Attention{
-		BaseInline:    ast.BaseInline{},
-		AttentionType: attentionType,
-	}
-}

modules/markup/markdown/callout/ast.go

@@ -0,0 +1,37 @@
+// Copyright 2020 The Gitea Authors. All rights reserved.
+// SPDX-License-Identifier: MIT
+
+package callout
+
+import (
+	"github.com/yuin/goldmark/ast"
+)
+
+// Attention is an inline for an attention
+type Attention struct {
+	ast.BaseInline
+	AttentionType string
+}
+
+// Dump implements Node.Dump.
+func (n *Attention) Dump(source []byte, level int) {
+	m := map[string]string{}
+	m["AttentionType"] = n.AttentionType
+	ast.DumpHelper(n, source, level, m, nil)
+}
+
+// KindAttention is the NodeKind for Attention
+var KindAttention = ast.NewNodeKind("Attention")
+
+// Kind implements Node.Kind.
+func (n *Attention) Kind() ast.NodeKind {
+	return KindAttention
+}
+
+// NewAttention returns a new Attention node.
+func NewAttention(attentionType string) *Attention {
+	return &Attention{
+		BaseInline:    ast.BaseInline{},
+		AttentionType: attentionType,
+	}
+}

modules/markup/markdown/callout/github.go

@@ -0,0 +1,142 @@
+// Copyright 2019 The Gitea Authors. All rights reserved.
+// Copyright 2024 The Forgejo Authors c/o Codeberg e.V.. All rights reserved.
+// SPDX-License-Identifier: MIT
+
+package callout
+
+import (
+	"strings"
+
+	"code.gitea.io/gitea/modules/svg"
+
+	"github.com/yuin/goldmark/ast"
+	"github.com/yuin/goldmark/parser"
+	"github.com/yuin/goldmark/renderer"
+	"github.com/yuin/goldmark/renderer/html"
+	"github.com/yuin/goldmark/text"
+	"github.com/yuin/goldmark/util"
+)
+
+type GitHubCalloutTransformer struct{}
+
+// Transform transforms the given AST tree.
+func (g *GitHubCalloutTransformer) Transform(node *ast.Document, reader text.Reader, pc parser.Context) {
+	supportedAttentionTypes := map[string]bool{
+		"note":      true,
+		"tip":       true,
+		"important": true,
+		"warning":   true,
+		"caution":   true,
+	}
+
+	_ = ast.Walk(node, func(n ast.Node, entering bool) (ast.WalkStatus, error) {
+		if !entering {
+			return ast.WalkContinue, nil
+		}
+
+		switch v := n.(type) {
+		case *ast.Blockquote:
+			// We only want attention blockquotes when the AST looks like:
+			// Text: "["
+			// Text: "!TYPE"
+			// Text(SoftLineBreak): "]"
+
+			// grab these nodes and make sure we adhere to the attention blockquote structure
+			firstParagraph := v.FirstChild()
+			if firstParagraph.ChildCount() < 3 {
+				return ast.WalkContinue, nil
+			}
+			firstTextNode, ok := firstParagraph.FirstChild().(*ast.Text)
+			if !ok || string(firstTextNode.Text(reader.Source())) != "[" {
+				return ast.WalkContinue, nil
+			}
+			secondTextNode, ok := firstTextNode.NextSibling().(*ast.Text)
+			if !ok {
+				return ast.WalkContinue, nil
+			}
+			// If the second node's text isn't one of the supported attention
+			// types, continue walking.
+			secondTextNodeText := secondTextNode.Text(reader.Source())
+			attentionType := strings.ToLower(strings.TrimPrefix(string(secondTextNodeText), "!"))
+			if _, has := supportedAttentionTypes[attentionType]; !has {
+				return ast.WalkContinue, nil
+			}
+
+			thirdTextNode, ok := secondTextNode.NextSibling().(*ast.Text)
+			if !ok || string(thirdTextNode.Text(reader.Source())) != "]" {
+				return ast.WalkContinue, nil
+			}
+
+			// color the blockquote
+			v.SetAttributeString("class", []byte("gt-py-3 attention attention-"+attentionType))
+
+			// create an emphasis to make it bold
+			emphasis := ast.NewEmphasis(2)
+			emphasis.SetAttributeString("class", []byte("attention-"+attentionType))
+			firstParagraph.InsertBefore(firstParagraph, firstTextNode, emphasis)
+
+			// capitalize first letter
+			attentionText := ast.NewString([]byte(strings.ToUpper(string(attentionType[0])) + attentionType[1:]))
+
+			// replace the ![TYPE] with icon+Type
+			emphasis.AppendChild(emphasis, attentionText)
+			for i := 0; i < 2; i++ {
+				lineBreak := ast.NewText()
+				lineBreak.SetSoftLineBreak(true)
+				firstParagraph.InsertAfter(firstParagraph, emphasis, lineBreak)
+			}
+			firstParagraph.InsertBefore(firstParagraph, emphasis, NewAttention(attentionType))
+			firstParagraph.RemoveChild(firstParagraph, firstTextNode)
+			firstParagraph.RemoveChild(firstParagraph, secondTextNode)
+			firstParagraph.RemoveChild(firstParagraph, thirdTextNode)
+		}
+		return ast.WalkContinue, nil
+	})
+}
+
+type GitHubCalloutHTMLRenderer struct {
+	html.Config
+}
+
+// RegisterFuncs implements renderer.NodeRenderer.RegisterFuncs.
+func (r *GitHubCalloutHTMLRenderer) RegisterFuncs(reg renderer.NodeRendererFuncRegisterer) {
+	reg.Register(KindAttention, r.renderAttention)
+}
+
+// renderAttention renders a quote marked with i.e. "> **Note**" or "> **Warning**" with a corresponding svg
+func (r *GitHubCalloutHTMLRenderer) renderAttention(w util.BufWriter, source []byte, node ast.Node, entering bool) (ast.WalkStatus, error) {
+	if entering {
+		_, _ = w.WriteString(`<span class="gt-mr-2 gt-vm attention-`)
+		n := node.(*Attention)
+		_, _ = w.WriteString(strings.ToLower(n.AttentionType))
+		_, _ = w.WriteString(`">`)
+
+		var octiconType string
+		switch n.AttentionType {
+		case "note":
+			octiconType = "info"
+		case "tip":
+			octiconType = "light-bulb"
+		case "important":
+			octiconType = "report"
+		case "warning":
+			octiconType = "alert"
+		case "caution":
+			octiconType = "stop"
+		}
+		_, _ = w.WriteString(string(svg.RenderHTML("octicon-" + octiconType)))
+	} else {
+		_, _ = w.WriteString("</span>\n")
+	}
+	return ast.WalkContinue, nil
+}
+
+func NewGitHubCalloutHTMLRenderer(opts ...html.Option) renderer.NodeRenderer {
+	r := &GitHubCalloutHTMLRenderer{
+		Config: html.NewConfig(),
+	}
+	for _, opt := range opts {
+		opt.SetHTMLOption(&r.Config)
+	}
+	return r
+}

modules/markup/markdown/goldmark.go

@@ -13,7 +13,6 @@ import (
 	"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"
@@ -196,55 +195,6 @@ func (g *ASTTransformer) Transform(node *ast.Document, reader text.Reader, pc pa
 			if css.ColorHandler(strings.ToLower(string(colorContent))) {
 				v.AppendChild(v, NewColorPreview(colorContent))
 			}
-		case *ast.Blockquote:
-			// We only want attention blockquotes when the AST looks like:
-			// Text: "["
-			// Text: "!TYPE"
-			// Text(SoftLineBreak): "]"
-
-			// grab these nodes and make sure we adhere to the attention blockquote structure
-			firstParagraph := v.FirstChild()
-			if firstParagraph.ChildCount() < 3 {
-				return ast.WalkContinue, nil
-			}
-			firstTextNode, ok := firstParagraph.FirstChild().(*ast.Text)
-			if !ok || string(firstTextNode.Segment.Value(reader.Source())) != "[" {
-				return ast.WalkContinue, nil
-			}
-			secondTextNode, ok := firstTextNode.NextSibling().(*ast.Text)
-			if !ok || !attentionTypeRE.MatchString(string(secondTextNode.Segment.Value(reader.Source()))) {
-				return ast.WalkContinue, nil
-			}
-			thirdTextNode, ok := secondTextNode.NextSibling().(*ast.Text)
-			if !ok || string(thirdTextNode.Segment.Value(reader.Source())) != "]" {
-				return ast.WalkContinue, nil
-			}
-
-			// grab attention type from markdown source
-			attentionType := strings.ToLower(strings.TrimPrefix(string(secondTextNode.Segment.Value(reader.Source())), "!"))
-
-			// color the blockquote
-			v.SetAttributeString("class", []byte("gt-py-3 attention attention-"+attentionType))
-
-			// create an emphasis to make it bold
-			emphasis := ast.NewEmphasis(2)
-			emphasis.SetAttributeString("class", []byte("attention-"+attentionType))
-			firstParagraph.InsertBefore(firstParagraph, firstTextNode, emphasis)
-
-			// capitalize first letter
-			attentionText := ast.NewString([]byte(strings.ToUpper(string(attentionType[0])) + attentionType[1:]))
-
-			// replace the ![TYPE] with icon+Type
-			emphasis.AppendChild(emphasis, attentionText)
-			for i := 0; i < 2; i++ {
-				lineBreak := ast.NewText()
-				lineBreak.SetSoftLineBreak(true)
-				firstParagraph.InsertAfter(firstParagraph, emphasis, lineBreak)
-			}
-			firstParagraph.InsertBefore(firstParagraph, emphasis, NewAttention(attentionType))
-			firstParagraph.RemoveChild(firstParagraph, firstTextNode)
-			firstParagraph.RemoveChild(firstParagraph, secondTextNode)
-			firstParagraph.RemoveChild(firstParagraph, thirdTextNode)
 		}
 		return ast.WalkContinue, nil
 	})
@@ -335,7 +285,6 @@ func (r *HTMLRenderer) RegisterFuncs(reg renderer.NodeRendererFuncRegisterer) {
 	reg.Register(KindSummary, r.renderSummary)
 	reg.Register(KindIcon, r.renderIcon)
 	reg.Register(ast.KindCodeSpan, r.renderCodeSpan)
-	reg.Register(KindAttention, r.renderAttention)
 	reg.Register(KindTaskCheckBoxListItem, r.renderTaskCheckBoxListItem)
 	reg.Register(east.KindTaskCheckBox, r.renderTaskCheckBox)
 }
@@ -372,34 +321,6 @@ func (r *HTMLRenderer) renderCodeSpan(w util.BufWriter, source []byte, n ast.Nod
 	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 {
-		_, _ = w.WriteString(`<span class="gt-mr-2 gt-vm attention-`)
-		n := node.(*Attention)
-		_, _ = w.WriteString(strings.ToLower(n.AttentionType))
-		_, _ = w.WriteString(`">`)
-
-		var octiconType string
-		switch n.AttentionType {
-		case "note":
-			octiconType = "info"
-		case "tip":
-			octiconType = "light-bulb"
-		case "important":
-			octiconType = "report"
-		case "warning":
-			octiconType = "alert"
-		case "caution":
-			octiconType = "stop"
-		}
-		_, _ = w.WriteString(string(svg.RenderHTML("octicon-" + octiconType)))
-	} else {
-		_, _ = w.WriteString("</span>\n")
-	}
-	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)
 
@@ -459,10 +380,7 @@ func (r *HTMLRenderer) renderSummary(w util.BufWriter, source []byte, node ast.N
 	return ast.WalkContinue, nil
 }
 
-var (
-	validNameRE     = regexp.MustCompile("^[a-z ]+$")
-	attentionTypeRE = regexp.MustCompile("^!(NOTE|TIP|IMPORTANT|WARNING|CAUTION)$")
-)
+var validNameRE = regexp.MustCompile("^[a-z ]+$")
 
 func (r *HTMLRenderer) renderIcon(w util.BufWriter, source []byte, node ast.Node, entering bool) (ast.WalkStatus, error) {
 	if !entering {

modules/markup/markdown/markdown.go

@@ -13,6 +13,7 @@ import (
 	"code.gitea.io/gitea/modules/log"
 	"code.gitea.io/gitea/modules/markup"
 	"code.gitea.io/gitea/modules/markup/common"
+	"code.gitea.io/gitea/modules/markup/markdown/callout"
 	"code.gitea.io/gitea/modules/markup/markdown/math"
 	"code.gitea.io/gitea/modules/setting"
 	giteautil "code.gitea.io/gitea/modules/util"
@@ -124,6 +125,7 @@ func SpecializedMarkdown() goldmark.Markdown {
 				parser.WithAttribute(),
 				parser.WithAutoHeadingID(),
 				parser.WithASTTransformers(
+					util.Prioritized(&callout.GitHubCalloutTransformer{}, 9000),
 					util.Prioritized(&ASTTransformer{}, 10000),
 				),
 			),
@@ -135,6 +137,7 @@ func SpecializedMarkdown() goldmark.Markdown {
 		// Override the original Tasklist renderer!
 		specMarkdown.Renderer().AddOptions(
 			renderer.WithNodeRenderers(
+				util.Prioritized(callout.NewGitHubCalloutHTMLRenderer(), 10),
 				util.Prioritized(NewHTMLRenderer(), 10),
 			),
 		)