Add WithAttribute

README.md

@@ -91,6 +91,7 @@ Parser and Renderer options
 | `parser.WithInlineParsers` | A `util.PrioritizedSlice` whose elements are `parser.InlineParser` | Parsers for parsing inline level elements. | 
 | `parser.WithParagraphTransformers` | A `util.PrioritizedSlice` whose elements are `parser.ParagraphTransformer` | Transformers for transforming paragraph nodes. | 
 | `parser.WithAutoHeadingID` | `-` | Enables auto heading ids. |
+| `parser.WithAttribute` | `-` | Enables custom attributes. Currently only headings supports attributes. |
 | `parser.WithFilterTags` | `...string` | HTML tag names forbidden in HTML blocks and Raw HTMLs. |
 
 ### HTML Renderer options
@@ -120,6 +121,23 @@ Parser and Renderer options
 - `extension.Footnote`
   - [PHP Markdown Extra: Footnotes](https://michelf.ca/projects/php-markdown/extra/#footnotes)
 
+### Attributes
+`parser.WithAttribute` option allows you to define attributes on some elements.
+
+Currently only headings supports attributes.
+
+#### Headings
+
+```
+## heading ## {#id .className attrName=attrValue class="class1 class2"}
+```
+
+```
+heading {#id .className attrName=attrValue}
+============
+```
+
+
 Create extensions
 --------------------
 **TODO**

ast/ast.go

@@ -157,6 +157,9 @@ type Node interface {
 	// Attributes returns a list of attributes.
 	// This may be a nil if there are no attributes.
 	Attributes() []Attribute
+
+	// RemoveAttributes removes all attributes from this node.
+	RemoveAttributes()
 }
 
 // A BaseNode struct implements the Node interface.
@@ -371,6 +374,11 @@ func (n *BaseNode) Attributes() []Attribute {
 	return n.attributes
 }
 
+// RemoveAttributes implements Node.RemoveAttributes
+func (n *BaseNode) RemoveAttributes() {
+	n.attributes = nil
+}
+
 // DumpHelper is a helper function to implement Node.Dump.
 // kv is pairs of an attribute name and an attribute value.
 // cb is a function called after wrote a name and attributes.

parser/atx_heading.go

@@ -4,12 +4,12 @@ import (
 	"github.com/yuin/goldmark/ast"
 	"github.com/yuin/goldmark/text"
 	"github.com/yuin/goldmark/util"
-	"regexp"
 )
 
 // A HeadingConfig struct is a data structure that holds configuration of the renderers related to headings.
 type HeadingConfig struct {
 	AutoHeadingID bool
+	Attribute     bool
 }
 
 // SetOption implements SetOptioner.
@@ -17,11 +17,14 @@ func (b *HeadingConfig) SetOption(name OptionName, value interface{}) {
 	switch name {
 	case AutoHeadingID:
 		b.AutoHeadingID = true
+	case Attribute:
+		b.Attribute = true
 	}
 }
 
 // A HeadingOption interface sets options for heading parsers.
 type HeadingOption interface {
+	Option
 	SetHeadingOption(*HeadingConfig)
 }
 
@@ -31,7 +34,7 @@ var AutoHeadingID OptionName = "AutoHeadingID"
 type withAutoHeadingID struct {
 }
 
-func (o *withAutoHeadingID) SetConfig(c *Config) {
+func (o *withAutoHeadingID) SetParserOption(c *Config) {
 	c.Options[AutoHeadingID] = true
 }
 
@@ -41,14 +44,22 @@ func (o *withAutoHeadingID) SetHeadingOption(p *HeadingConfig) {
 
 // WithAutoHeadingID is a functional option that enables custom heading ids and
 // auto generated heading ids.
-func WithAutoHeadingID() interface {
-	Option
-	HeadingOption
-} {
+func WithAutoHeadingID() HeadingOption {
 	return &withAutoHeadingID{}
 }
 
-var atxHeadingRegexp = regexp.MustCompile(`^[ ]{0,3}(#{1,6})(?:\s+(.*?)\s*([\s]#+\s*)?)?\n?$`)
+type withHeadingAttribute struct {
+	Option
+}
+
+func (o *withHeadingAttribute) SetHeadingOption(p *HeadingConfig) {
+	p.Attribute = true
+}
+
+// WithHeadingAttribute is a functional option that enables custom heading attributes.
+func WithHeadingAttribute() HeadingOption {
+	return &withHeadingAttribute{WithAttribute()}
+}
 
 type atxHeadingParser struct {
 	HeadingConfig
@@ -79,22 +90,70 @@ func (b *atxHeadingParser) Open(parent ast.Node, reader text.Reader, pc Context)
 	}
 	start := i + l
 	stop := len(line) - util.TrimRightSpaceLength(line)
-	if stop <= start { // empty headings like '##[space]'
-		stop = start + 1
-	} else {
-		i = stop - 1
-		for ; line[i] == '#' && i >= start; i-- {
-		}
-		if i != stop-1 && !util.IsSpace(line[i]) {
-			i = stop - 1
-		}
-		i++
-		stop = i
-	}
 
 	node := ast.NewHeading(level)
-	if len(util.TrimRight(line[start:stop], []byte{'#'})) != 0 { // empty heading like '### ###'
-		node.Lines().Append(text.NewSegment(segment.Start+start, segment.Start+stop))
+	parsed := false
+	if b.Attribute { // handles special case like ### heading ### {#id}
+		start--
+		closureOpen := -1
+		closureClose := -1
+		for i := start; i < stop; {
+			c := line[i]
+			if util.IsEscapedPunctuation(line, i) {
+				i += 2
+			} else if util.IsSpace(c) && i < stop-1 && line[i+1] == '#' {
+				closureOpen = i + 1
+				j := i + 1
+				for ; j < stop && line[j] == '#'; j++ {
+				}
+				closureClose = j
+				break
+			} else {
+				i++
+			}
+		}
+		if closureClose > 0 {
+			i := closureClose
+			for ; i < stop && util.IsSpace(line[i]); i++ {
+			}
+			if i < stop-1 || line[i] == '{' {
+				as := i + 1
+				for as < stop {
+					ai := util.FindAttributeIndex(line[as:], true)
+					if ai[0] < 0 {
+						break
+					}
+					node.SetAttribute(line[as+ai[0]:as+ai[1]],
+						line[as+ai[2]:as+ai[3]])
+					as += ai[3]
+				}
+				if line[as] == '}' && (as > stop-2 || util.IsBlank(line[as:])) {
+					parsed = true
+					node.Lines().Append(text.NewSegment(segment.Start+start+1, segment.Start+closureOpen))
+				} else {
+					node.RemoveAttributes()
+				}
+			}
+		}
+	}
+	if !parsed {
+		stop := len(line) - util.TrimRightSpaceLength(line)
+		if stop <= start { // empty headings like '##[space]'
+			stop = start + 1
+		} else {
+			i = stop - 1
+			for ; line[i] == '#' && i >= start; i-- {
+			}
+			if i != stop-1 && !util.IsSpace(line[i]) {
+				i = stop - 1
+			}
+			i++
+			stop = i
+		}
+
+		if len(util.TrimRight(line[start:stop], []byte{'#'})) != 0 { // empty heading like '### ###'
+			node.Lines().Append(text.NewSegment(segment.Start+start, segment.Start+stop))
+		}
 	}
 	return node, NoChildren
 }
@@ -107,7 +166,12 @@ func (b *atxHeadingParser) Close(node ast.Node, reader text.Reader, pc Context)
 	if !b.AutoHeadingID {
 		return
 	}
-	generateAutoHeadingID(node.(*ast.Heading), reader, pc)
+	if !b.Attribute {
+		_, ok := node.AttributeString("id")
+		if !ok {
+			generateAutoHeadingID(node.(*ast.Heading), reader, pc)
+		}
+	}
 }
 
 func (b *atxHeadingParser) CanInterruptParagraph() bool {

parser/html_block.go

@@ -34,7 +34,7 @@ type withFilterTags struct {
 	value map[string]bool
 }
 
-func (o *withFilterTags) SetConfig(c *Config) {
+func (o *withFilterTags) SetParserOption(c *Config) {
 	c.Options[FilterTags] = o.value
 }
 

parser/parser.go

@@ -375,12 +375,27 @@ func NewConfig() *Config {
 
 // An Option interface is a functional option type for the Parser.
 type Option interface {
-	SetConfig(*Config)
+	SetParserOption(*Config)
 }
 
 // OptionName is a name of parser options.
 type OptionName string
 
+// Attribute is an option name that spacify attributes of elements.
+const Attribute OptionName = "Attribute"
+
+type withAttribute struct {
+}
+
+func (o *withAttribute) SetParserOption(c *Config) {
+	c.Options[Attribute] = true
+}
+
+// WithAttribute is a functional option that enables custom attributes.
+func WithAttribute() Option {
+	return &withAttribute{}
+}
+
 // A Parser interface parses Markdown text into AST nodes.
 type Parser interface {
 	// Parse parses the given Markdown text into AST nodes.
@@ -552,7 +567,7 @@ type withBlockParsers struct {
 	value []util.PrioritizedValue
 }
 
-func (o *withBlockParsers) SetConfig(c *Config) {
+func (o *withBlockParsers) SetParserOption(c *Config) {
 	c.BlockParsers = append(c.BlockParsers, o.value...)
 }
 
@@ -566,7 +581,7 @@ type withInlineParsers struct {
 	value []util.PrioritizedValue
 }
 
-func (o *withInlineParsers) SetConfig(c *Config) {
+func (o *withInlineParsers) SetParserOption(c *Config) {
 	c.InlineParsers = append(c.InlineParsers, o.value...)
 }
 
@@ -580,7 +595,7 @@ type withParagraphTransformers struct {
 	value []util.PrioritizedValue
 }
 
-func (o *withParagraphTransformers) SetConfig(c *Config) {
+func (o *withParagraphTransformers) SetParserOption(c *Config) {
 	c.ParagraphTransformers = append(c.ParagraphTransformers, o.value...)
 }
 
@@ -594,7 +609,7 @@ type withASTTransformers struct {
 	value []util.PrioritizedValue
 }
 
-func (o *withASTTransformers) SetConfig(c *Config) {
+func (o *withASTTransformers) SetParserOption(c *Config) {
 	c.ASTTransformers = append(c.ASTTransformers, o.value...)
 }
 
@@ -609,7 +624,7 @@ type withOption struct {
 	value interface{}
 }
 
-func (o *withOption) SetConfig(c *Config) {
+func (o *withOption) SetParserOption(c *Config) {
 	c.Options[o.name] = o.value
 }
 
@@ -623,7 +638,7 @@ func WithOption(name OptionName, value interface{}) Option {
 func NewParser(options ...Option) Parser {
 	config := NewConfig()
 	for _, opt := range options {
-		opt.SetConfig(config)
+		opt.SetParserOption(config)
 	}
 
 	p := &parser{
@@ -636,7 +651,7 @@ func NewParser(options ...Option) Parser {
 
 func (p *parser) AddOptions(opts ...Option) {
 	for _, opt := range opts {
-		opt.SetConfig(p.config)
+		opt.SetParserOption(p.config)
 	}
 }
 

parser/setext_headings.go

@@ -94,10 +94,27 @@ func (b *setextHeadingParser) Close(node ast.Node, reader text.Reader, pc Contex
 		tmp.Parent().RemoveChild(tmp.Parent(), tmp)
 	}
 
-	if !b.AutoHeadingID {
-		return
+	if b.Attribute {
+		lastIndex := node.Lines().Len() - 1
+		lastLine := node.Lines().At(lastIndex)
+		line := lastLine.Value(reader.Source())
+		indicies := util.FindAttributeIndiciesReverse(line, true)
+		if indicies != nil {
+			for _, index := range indicies {
+				node.SetAttribute(line[index[0]:index[1]], line[index[2]:index[3]])
+			}
+			lastLine.Stop = lastLine.Start + indicies[0][0] - 1
+			lastLine.TrimRightSpace(reader.Source())
+			node.Lines().Set(lastIndex, lastLine)
+		}
+	}
+
+	if b.AutoHeadingID {
+		_, ok := node.AttributeString("id")
+		if !ok {
+			generateAutoHeadingID(heading, reader, pc)
+		}
 	}
-	generateAutoHeadingID(heading, reader, pc)
 }
 
 func (b *setextHeadingParser) CanInterruptParagraph() bool {

renderer/html/html.go

@@ -206,12 +206,7 @@ func (r *Renderer) renderHeading(w util.BufWriter, source []byte, node ast.Node,
 		w.WriteString("<h")
 		w.WriteByte("0123456"[n.Level])
 		if n.Attributes() != nil {
-			id, ok := n.Attribute(attrNameID)
-			if ok {
-				w.WriteString(` id="`)
-				w.Write(id)
-				w.WriteByte('"')
-			}
+			r.RenderAttributes(w, node)
 		}
 		w.WriteByte('>')
 	} else {
@@ -491,6 +486,17 @@ func (r *Renderer) renderText(w util.BufWriter, source []byte, node ast.Node, en
 	return ast.WalkContinue, nil
 }
 
+// RenderAttributes renders given node's attributes.
+func (r *Renderer) RenderAttributes(w util.BufWriter, node ast.Node) {
+	for _, attr := range node.Attributes() {
+		w.WriteString(" ")
+		w.Write(attr.Name)
+		w.WriteString(`="`)
+		w.Write(attr.Value)
+		w.WriteByte('"')
+	}
+}
+
 // A Writer interface wirtes textual contents to a writer.
 type Writer interface {
 	// Write writes the given source to writer with resolving references and unescaping

util/util.go

@@ -54,6 +54,12 @@ func (b *CopyOnWriteBuffer) IsCopied() bool {
 	return b.copied
 }
 
+// IsEscapedPunctuation returns true if caracter at a given index i
+// is an escaped punctuation, otherwise false.
+func IsEscapedPunctuation(source []byte, i int) bool {
+	return source[i] == '\\' && i < len(source)-1 && IsPunct(source[i+1])
+}
+
 // ReadWhile read the given source while pred is true.
 func ReadWhile(source []byte, index [2]int, pred func(byte) bool) (int, bool) {
 	j := index[0]
@@ -549,6 +555,46 @@ func URLEscape(v []byte, resolveReference bool) []byte {
 	return cob.Bytes()
 }
 
+// FindAttributeIndiciesReverse searches attribute indicies from tail of the given
+// bytes and returns indicies.
+func FindAttributeIndiciesReverse(b []byte, canEscapeQuotes bool) [][4]int {
+	i := 0
+retry:
+	var result [][4]int
+	as := -1
+	for i < len(b) {
+		if IsEscapedPunctuation(b, i) {
+			i += 2
+			continue
+		}
+		if b[i] == '{' {
+			i++
+			as = i
+			break
+		}
+		i++
+	}
+	if as < 0 {
+		return nil
+	}
+	for as < len(b) {
+		ai := FindAttributeIndex(b[as:], canEscapeQuotes)
+		if ai[0] < 0 {
+			break
+		}
+		i = as + ai[3]
+		if result == nil {
+			result = [][4]int{}
+		}
+		result = append(result, [4]int{as + ai[0], as + ai[1], as + ai[2], as + ai[3]})
+		as += ai[3]
+	}
+	if b[as] == '}' && (as > len(b)-2 || IsBlank(b[as:])) {
+		return result
+	}
+	goto retry
+}
+
 // FindAttributeIndex searchs
 //     - #id
 //     - .class
@@ -613,10 +659,10 @@ func FindHTMLAttributeIndex(b []byte, canEscapeQuotes bool) [4]int {
 	for ; i < l && IsSpace(b[i]); i++ {
 	}
 	if i >= l {
-		return result // empty attribute
+		return [4]int{-1, -1, -1, -1}
 	}
 	if b[i] != '=' {
-		return result // empty attribute
+		return [4]int{-1, -1, -1, -1}
 	}
 	i++
 	for ; i < l && IsSpace(b[i]); i++ {