Add autoID for definition terms

Fixes #13403
See #11566

Co-authored-by: Joe Mooring <joe@mooring.com>

markup/goldmark/internal/extensions/attributes/attributes.go

@@ -1,8 +1,11 @@
 package attributes
 
 import (
+	"github.com/gohugoio/hugo/markup/goldmark/goldmark_config"
+	"github.com/gohugoio/hugo/markup/goldmark/internal/render"
 	"github.com/yuin/goldmark"
 	"github.com/yuin/goldmark/ast"
+	east "github.com/yuin/goldmark/extension/ast"
 	"github.com/yuin/goldmark/parser"
 	"github.com/yuin/goldmark/text"
 	"github.com/yuin/goldmark/util"
@@ -14,24 +17,29 @@ import (
 
 var (
 	kindAttributesBlock = ast.NewNodeKind("AttributesBlock")
+	attrNameID          = []byte("id")
 
-	defaultParser                        = new(attrParser)
-	defaultTransformer                   = new(transformer)
-	attributes         goldmark.Extender = new(attrExtension)
+	defaultParser = new(attrParser)
 )
 
-func New() goldmark.Extender {
-	return attributes
+func New(cfg goldmark_config.Parser) goldmark.Extender {
+	return &attrExtension{cfg: cfg}
 }
 
-type attrExtension struct{}
+type attrExtension struct {
+	cfg goldmark_config.Parser
+}
 
 func (a *attrExtension) Extend(m goldmark.Markdown) {
+	if a.cfg.Attribute.Block {
+		m.Parser().AddOptions(
+			parser.WithBlockParsers(
+				util.Prioritized(defaultParser, 100)),
+		)
+	}
 	m.Parser().AddOptions(
-		parser.WithBlockParsers(
-			util.Prioritized(defaultParser, 100)),
 		parser.WithASTTransformers(
-			util.Prioritized(defaultTransformer, 100),
+			util.Prioritized(&transformer{cfg: a.cfg}, 100),
 		),
 	)
 }
@@ -92,18 +100,47 @@ func (a *attributesBlock) Kind() ast.NodeKind {
 	return kindAttributesBlock
 }
 
-type transformer struct{}
+type transformer struct {
+	cfg goldmark_config.Parser
+}
+
+func (a *transformer) isFragmentNode(n ast.Node) bool {
+	switch n.Kind() {
+	case east.KindDefinitionTerm, ast.KindHeading:
+		return true
+	default:
+		return false
+	}
+}
 
 func (a *transformer) Transform(node *ast.Document, reader text.Reader, pc parser.Context) {
-	attributes := make([]ast.Node, 0, 500)
+	var attributes []ast.Node
+	if a.cfg.Attribute.Block {
+		attributes = make([]ast.Node, 0, 500)
+	}
 	ast.Walk(node, func(node ast.Node, entering bool) (ast.WalkStatus, error) {
-		if entering && node.Kind() == kindAttributesBlock {
+		if !entering {
+			return ast.WalkContinue, nil
+		}
+
+		if a.isFragmentNode(node) {
+			if id, found := node.Attribute(attrNameID); !found {
+				a.generateAutoID(node, reader, pc)
+			} else {
+				pc.IDs().Put(id.([]byte))
+			}
+		}
+
+		if a.cfg.Attribute.Block && node.Kind() == kindAttributesBlock {
 			// Attributes for fenced code blocks are handled in their own extension,
 			// but note that we currently only support code block attributes when
 			// CodeFences=true.
 			if node.PreviousSibling() != nil && node.PreviousSibling().Kind() != ast.KindFencedCodeBlock && !node.HasBlankPreviousLines() {
 				attributes = append(attributes, node)
 				return ast.WalkSkipChildren, nil
+			} else {
+				// remove attributes node
+				node.Parent().RemoveChild(node.Parent(), node)
 			}
 		}
 
@@ -123,3 +160,33 @@ func (a *transformer) Transform(node *ast.Document, reader text.Reader, pc parse
 		attr.Parent().RemoveChild(attr.Parent(), attr)
 	}
 }
+
+func (a *transformer) generateAutoID(n ast.Node, reader text.Reader, pc parser.Context) {
+	var text []byte
+	switch n := n.(type) {
+	case *ast.Heading:
+		if a.cfg.AutoHeadingID {
+			text = textHeadingID(n, reader)
+		}
+	case *east.DefinitionTerm:
+		if a.cfg.AutoDefinitionTermID {
+			text = []byte(render.TextPlain(n, reader.Source()))
+		}
+	}
+
+	if len(text) > 0 {
+		headingID := pc.IDs().Generate(text, n.Kind())
+		n.SetAttribute(attrNameID, headingID)
+	}
+}
+
+// Markdown settext headers can have multiple lines, use the last line for the ID.
+func textHeadingID(node *ast.Heading, reader text.Reader) []byte {
+	var line []byte
+	lastIndex := node.Lines().Len() - 1
+	if lastIndex > -1 {
+		lastLine := node.Lines().At(lastIndex)
+		line = lastLine.Value(reader.Source())
+	}
+	return line
+}