html: implement fragment parsing algorithm

Pass the tests in tests4.dat.

R=nigeltao
CC=golang-dev
https://golang.org/cl/5447055

src/pkg/html/parse.go

@@ -39,6 +39,9 @@ type parser struct {
 	fosterParenting bool
 	// quirks is whether the parser is operating in "quirks mode."
 	quirks bool
+	// context is the context element when parsing an HTML fragment
+	// (section 11.4).
+	context *Node
 }
 
 func (p *parser) top() *Node {
@@ -287,9 +290,10 @@ func (p *parser) setOriginalIM() {
 func (p *parser) resetInsertionMode() {
 	for i := len(p.oe) - 1; i >= 0; i-- {
 		n := p.oe[i]
-		if i == 0 {
-			// TODO: set n to the context element, for HTML fragment parsing.
+		if i == 0 && p.context != nil {
+			n = p.context
 		}
+
 		switch n.Data {
 		case "select":
 			p.im = inSelectIM
@@ -1516,18 +1520,7 @@ func afterAfterFramesetIM(p *parser) bool {
 	return true
 }
 
-// Parse returns the parse tree for the HTML from the given Reader.
-// The input is assumed to be UTF-8 encoded.
-func Parse(r io.Reader) (*Node, error) {
-	p := &parser{
-		tokenizer: NewTokenizer(r),
-		doc: &Node{
-			Type: DocumentNode,
-		},
-		scripting:  true,
-		framesetOK: true,
-		im:         initialIM,
-	}
+func (p *parser) parse() error {
 	// Iterate until EOF. Any other error will cause an early return.
 	consumed := true
 	for {
@@ -1536,7 +1529,7 @@ func Parse(r io.Reader) (*Node, error) {
 				if err == io.EOF {
 					break
 				}
-				return nil, err
+				return err
 			}
 		}
 		consumed = p.im(p)
@@ -1547,5 +1540,77 @@ func Parse(r io.Reader) (*Node, error) {
 			break
 		}
 	}
+	return nil
+}
+
+// Parse returns the parse tree for the HTML from the given Reader.
+// The input is assumed to be UTF-8 encoded.
+func Parse(r io.Reader) (*Node, error) {
+	p := &parser{
+		tokenizer: NewTokenizer(r),
+		doc: &Node{
+			Type: DocumentNode,
+		},
+		scripting:  true,
+		framesetOK: true,
+		im:         initialIM,
+	}
+	err := p.parse()
+	if err != nil {
+		return nil, err
+	}
 	return p.doc, nil
 }
+
+// ParseFragment parses a fragment of HTML and returns the nodes that were 
+// found. If the fragment is the InnerHTML for an existing element, pass that
+// element in context.
+func ParseFragment(r io.Reader, context *Node) ([]*Node, error) {
+	p := &parser{
+		tokenizer: NewTokenizer(r),
+		doc: &Node{
+			Type: DocumentNode,
+		},
+		scripting: true,
+		context:   context,
+	}
+
+	if context != nil {
+		switch context.Data {
+		case "iframe", "noembed", "noframes", "noscript", "plaintext", "script", "style", "title", "textarea", "xmp":
+			p.tokenizer.rawTag = context.Data
+		}
+	}
+
+	root := &Node{
+		Type: ElementNode,
+		Data: "html",
+	}
+	p.doc.Add(root)
+	p.oe = nodeStack{root}
+	p.resetInsertionMode()
+
+	for n := context; n != nil; n = n.Parent {
+		if n.Type == ElementNode && n.Data == "form" {
+			p.form = n
+			break
+		}
+	}
+
+	err := p.parse()
+	if err != nil {
+		return nil, err
+	}
+
+	parent := p.doc
+	if context != nil {
+		parent = root
+	}
+
+	result := parent.Child
+	parent.Child = nil
+	for _, n := range result {
+		n.Parent = nil
+	}
+	return result, nil
+}

src/pkg/html/parse_test.go

@@ -16,21 +16,21 @@ import (
 )
 
 // readParseTest reads a single test case from r.
-func readParseTest(r *bufio.Reader) (text, want string, err error) {
+func readParseTest(r *bufio.Reader) (text, want, context string, err error) {
 	line, err := r.ReadSlice('\n')
 	if err != nil {
-		return "", "", err
+		return "", "", "", err
 	}
 	var b []byte
 
 	// Read the HTML.
 	if string(line) != "#data\n" {
-		return "", "", fmt.Errorf(`got %q want "#data\n"`, line)
+		return "", "", "", fmt.Errorf(`got %q want "#data\n"`, line)
 	}
 	for {
 		line, err = r.ReadSlice('\n')
 		if err != nil {
-			return "", "", err
+			return "", "", "", err
 		}
 		if line[0] == '#' {
 			break
@@ -42,33 +42,45 @@ func readParseTest(r *bufio.Reader) (text, want string, err error) {
 
 	// Skip the error list.
 	if string(line) != "#errors\n" {
-		return "", "", fmt.Errorf(`got %q want "#errors\n"`, line)
+		return "", "", "", fmt.Errorf(`got %q want "#errors\n"`, line)
 	}
 	for {
 		line, err = r.ReadSlice('\n')
 		if err != nil {
-			return "", "", err
+			return "", "", "", err
 		}
 		if line[0] == '#' {
 			break
 		}
 	}
 
+	if string(line) == "#document-fragment\n" {
+		line, err = r.ReadSlice('\n')
+		if err != nil {
+			return "", "", "", err
+		}
+		context = strings.TrimSpace(string(line))
+		line, err = r.ReadSlice('\n')
+		if err != nil {
+			return "", "", "", err
+		}
+	}
+
 	// Read the dump of what the parse tree should be.
 	if string(line) != "#document\n" {
-		return "", "", fmt.Errorf(`got %q want "#document\n"`, line)
+		return "", "", "", fmt.Errorf(`got %q want "#document\n"`, line)
 	}
 	for {
 		line, err = r.ReadSlice('\n')
 		if err != nil && err != io.EOF {
-			return "", "", err
+			return "", "", "", err
 		}
 		if len(line) == 0 || len(line) == 1 && line[0] == '\n' {
 			break
 		}
 		b = append(b, line...)
 	}
-	return text, string(b), nil
+	return text, string(b), context, nil
 }
 
 func dumpIndent(w io.Writer, level int) {
@@ -153,7 +165,7 @@ func TestParser(t *testing.T) {
 		{"tests1.dat", -1},
 		{"tests2.dat", -1},
 		{"tests3.dat", -1},
-		// tests4.dat is fragment cases.
+		{"tests4.dat", -1},
 		{"tests5.dat", -1},
 	}
 	for _, tf := range testFiles {
@@ -164,17 +176,37 @@ func TestParser(t *testing.T) {
 		defer f.Close()
 		r := bufio.NewReader(f)
 		for i := 0; i != tf.n; i++ {
-			text, want, err := readParseTest(r)
+			text, want, context, err := readParseTest(r)
 			if err == io.EOF && tf.n == -1 {
 				break
 			}
 			if err != nil {
 				t.Fatal(err)
 			}
-			doc, err := Parse(strings.NewReader(text))
-			if err != nil {
-				t.Fatal(err)
+
+			var doc *Node
+			if context == "" {
+				doc, err = Parse(strings.NewReader(text))
+				if err != nil {
+					t.Fatal(err)
+				}
+			} else {
+				contextNode := &Node{
+					Type: ElementNode,
+					Data: context,
+				}
+				nodes, err := ParseFragment(strings.NewReader(text), contextNode)
+				if err != nil {
+					t.Fatal(err)
+				}
+				doc = &Node{
+					Type: DocumentNode,
+				}
+				for _, n := range nodes {
+					doc.Add(n)
+				}
 			}
+
 			got, err := dump(doc)
 			if err != nil {
 				t.Fatal(err)
@@ -184,7 +216,7 @@ func TestParser(t *testing.T) {
 				t.Errorf("%s test #%d %q, got vs want:\n----\n%s----\n%s----", tf.filename, i, text, got, want)
 				continue
 			}
-			if renderTestBlacklist[text] {
+			if renderTestBlacklist[text] || context != "" {
 				continue
 			}
 			// Check that rendering and re-parsing results in an identical tree.