xml: allow unquoted attribute values in non-Strict mode

HTML4 standard supports unquoted attibute values in certain cases
(http://www.w3.org/TR/REC-html40/intro/sgmltut.html#h-3.2.2).

R=rsc
CC=golang-dev
https://golang.org/cl/207095

src/pkg/xml/xml.go

@@ -589,14 +589,7 @@ func (p *Parser) RawToken() (Token, os.Error) {
 			return nil, p.err
 		}
 		p.space()
-		if b, ok = p.mustgetc(); !ok {
-			return nil, p.err
-		}
-		if b != '"' && b != '\'' {
-			p.err = SyntaxError("unquoted or missing attribute value in element")
-			return nil, p.err
-		}
-		data := p.text(int(b), false)
+		data := p.attrval()
 		if data == nil {
 			return nil, p.err
 		}
@@ -610,6 +603,40 @@ func (p *Parser) RawToken() (Token, os.Error) {
 	return StartElement{name, attr}, nil
 }
 
+func (p *Parser) attrval() []byte {
+	b, ok := p.mustgetc()
+	if !ok {
+		return nil
+	}
+	// Handle quoted attribute values
+	if b == '"' || b == '\'' {
+		return p.text(int(b), false)
+	}
+	// Handle unquoted attribute values for strict parsers
+	if p.Strict {
+		p.err = SyntaxError("unquoted or missing attribute value in element")
+		return nil
+	}
+	// Handle unquoted attribute values for unstrict parsers
+	p.ungetc(b)
+	p.buf.Reset()
+	for {
+		b, ok = p.mustgetc()
+		if !ok {
+			return nil
+		}
+		// http://www.w3.org/TR/REC-html40/intro/sgmltut.html#h-3.2.2
+		if 'a' <= b && b <= 'z' || 'A' <= b && b <= 'Z' ||
+			'0' <= b && b <= '9' || b == '_' || b == ':' || b == '-' {
+			p.buf.WriteByte(b)
+		} else {
+			p.ungetc(b)
+			break
+		}
+	}
+	return p.buf.Bytes()
+}
+
 // Skip spaces if any
 func (p *Parser) space() {
 	for {

src/pkg/xml/xml_test.go

@@ -298,3 +298,23 @@ func TestIssue569(t *testing.T) {
 		t.Fatalf("Expecting abcd")
 	}
 }
+
+func TestUnquotedAttrs(t *testing.T) {
+	data := "<tag attr=azAZ09:-_\t>"
+	p := NewParser(StringReader(data))
+	p.Strict = false
+	token, err := p.Token()
+	if _, ok := err.(SyntaxError); ok {
+		t.Errorf("Unexpected error: %v", err)
+	}
+	if token.(StartElement).Name.Local != "tag" {
+		t.Errorf("Unexpected tag name: %v", token.(StartElement).Name.Local)
+	}
+	attr := token.(StartElement).Attr[0]
+	if attr.Value != "azAZ09:-_" {
+		t.Errorf("Unexpected attribute value: %v", attr.Value)
+	}
+	if attr.Name.Local != "attr" {
+		t.Errorf("Unexpected attribute name: %v", attr.Name.Local)
+	}
+}