Support CSS Nesting (resolve #92)

css/lex.go

@@ -140,6 +140,13 @@ type Lexer struct {
 	r *parse.Input
 }
 
+func CloneLexer(l *Lexer) *Lexer {
+	rr := parse.CloneInput(l.r)
+	return &Lexer{
+		r: rr,
+	}
+}
+
 // NewLexer returns a new Lexer for a given io.Reader.
 func NewLexer(r *parse.Input) *Lexer {
 	return &Lexer{

css/parse.go

@@ -62,6 +62,12 @@ func (tt GrammarType) String() string {
 
 ////////////////////////////////////////////////////////////////
 
+func isCombinator(data byte) bool {
+	return data == ',' || data == '/' || data == ':' || data == '!' || data == '='
+}
+
+////////////////////////////////////////////////////////////////
+
 // State is the state function the parser currently is in.
 type State func(*Parser) GrammarType
 
@@ -147,6 +153,22 @@ func (p *Parser) Values() []Token {
 	return p.buf
 }
 
+func (p *Parser) CloneParser() *Parser {
+	return &Parser{
+		l:           CloneLexer(p.l),
+		state:       append([]State{}, p.state...),
+		err:         p.err,
+		buf:         append([]Token{}, p.buf...),
+		data:        append([]byte{}, p.data...),
+		tt:          p.tt,
+		keepWS:      p.keepWS,
+		prevWS:      p.prevWS,
+		prevEnd:     p.prevEnd,
+		prevComment: p.prevComment,
+		level:       p.level,
+	}
+}
+
 func (p *Parser) popToken(allowComment bool) (TokenType, []byte) {
 	p.prevWS = false
 	p.prevComment = false
@@ -207,12 +229,41 @@ func (p *Parser) parseDeclarationList() GrammarType {
 		return ErrorGrammar
 	} else if p.tt == AtKeywordToken {
 		return p.parseAtRule()
-	} else if p.tt == IdentToken || p.tt == DelimToken {
-		return p.parseDeclaration()
 	} else if p.tt == CustomPropertyNameToken {
 		return p.parseCustomProperty()
 	}
 
+	pp := p.CloneParser()
+	// peek until we find a colon or semicolon or data length is 1 and is a combinator ->
+	// not a child rule, but a declaration
+	isDeclaration := true
+	for pp.tt != ErrorToken {
+		if pp.tt == SemicolonToken || pp.tt == RightBraceToken {
+			isDeclaration = true
+			break
+		} else if pp.tt == LeftBraceToken {
+			isDeclaration = false
+			break
+		}
+		if len(pp.data) == 1 {
+			if pp.data[0] == '&' {
+				isDeclaration = false
+				break
+			}
+			if isCombinator(pp.data[0]) {
+				isDeclaration = true
+				break
+			}
+		}
+		pp.tt, pp.data = pp.popToken(false)
+	}
+
+	if !isDeclaration {
+		return p.parseQualifiedRule()
+	} else if p.tt == IdentToken || p.tt == DelimToken {
+		return p.parseDeclaration()
+	}
+
 	// parse error
 	p.initBuf()
 	p.l.r.Move(-len(p.data))
@@ -426,7 +477,7 @@ func (p *Parser) parseDeclaration() GrammarType {
 			}
 			p.level--
 		}
-		if len(data) == 1 && (data[0] == ',' || data[0] == '/' || data[0] == ':' || data[0] == '!' || data[0] == '=') {
+		if len(data) == 1 && isCombinator(data[0]) {
 			skipWS = true
 		} else if (p.prevWS || p.prevComment) && !skipWS {
 			p.pushBuf(WhitespaceToken, wsBytes)

css/parse_test.go

@@ -39,6 +39,8 @@ func TestParse(t *testing.T) {
 		{false, "@media { @viewport ; }", "@media{@viewport;}"},
 		{false, "@keyframes 'diagonal-slide' {  from { left: 0; top: 0; } to { left: 100px; top: 100px; } }", "@keyframes 'diagonal-slide'{from{left:0;top:0;}to{left:100px;top:100px;}}"},
 		{false, "@keyframes movingbox{0%{left:90%;}50%{left:10%;}100%{left:90%;}}", "@keyframes movingbox{0%{left:90%;}50%{left:10%;}100%{left:90%;}}"},
+		{false, "a { &:hover { color: #f4a; } }", "a{&:hover{color:#f4a;}}"},
+		{false, ".foo { .bar > &:hover span { backgroud: orange } ; }", ".foo{.bar>&:hover span{backgroud:orange;}}"},
 		{false, ".foo { color: #fff;}", ".foo{color:#fff;}"},
 		{false, ".foo { ; _color: #fff;}", ".foo{_color:#fff;}"},
 		{false, "a { color: red; border: 0; }", "a{color:red;border:0;}"},
@@ -81,7 +83,7 @@ func TestParse(t *testing.T) {
 		{false, "[class*=\"column\"]+[class*=\"column\"]:last-child{a:b;}", "[class*=\"column\"]+[class*=\"column\"]:last-child{a:b;}"},
 		{false, "@media { @viewport }", "@media{@viewport;}"},
 		{false, "table { @unknown }", "table{@unknown;}"},
-		{false, "a{@media{width:70%;} b{width:60%;}}", "a{@media{ERROR(width:70%;})ERROR(b{width:60%;})}"},
+		{false, "a{@media{width:70%;} b{width:60%;}}", "a{@media{ERROR(width:70%;})b{width:60%;}}"},
 
 		// early endings
 		{false, "selector{", "selector{"},

input.go

@@ -74,6 +74,15 @@ func NewInputBytes(b []byte) *Input {
 	return z
 }
 
+func CloneInput(z *Input) *Input {
+	return &Input{
+		buf:   append([]byte{}, z.buf...),
+		pos:   z.pos,
+		start: z.start,
+		err:   z.err,
+	}
+}
+
 // Restore restores the replaced byte past the end of the buffer by NULL.
 func (z *Input) Restore() {
 	if z.restore != nil {