Update on Antlr grammar

packages/less/src/parser-antlr/CssLexer.g4

@@ -11,18 +11,10 @@ fragment Newline
   : '\\n' | '\\r' '\\n'? | '\\f'
   ;
 
-fragment WS
+fragment Whitespace
   : ' ' | '\\t' | Newline
   ;
 
-/** 
- * Uses nongreedy wildcard
- * @see https://github.com/antlr/antlr4/blob/master/doc/wildcard.md
- */
-fragment Comment
-  : '/*' .*? '*/'
-  ;
-
 fragment Digit
   : '0'..'9'
   ;
@@ -34,7 +26,7 @@ fragment Hex
   ;
 
 fragment Unicode
-  : '\\' Hex (Hex Hex Hex Hex Hex)? WS? // 1 or 6 hex digits
+  : '\\' Hex (Hex Hex Hex Hex Hex)? Whitespace? // 1 or 6 hex digits
   ;
 
 fragment Escape
@@ -50,10 +42,6 @@ fragment SingleString
   : '\'' ('\\' | ~[\n\r\f'] | Newline | Escape) '\''
   ;
 
-fragment String
-  : DoubleString | SingleString
-  ;
-
 fragment NonAscii
   : '\u0240'..'\uffff'
   ;
@@ -87,7 +75,7 @@ fragment UrlFragment
   ;
 
 fragment Integer
-  : ('+' | '-')? ('0'..'9')+
+  : ('+' | '-')? Digit+
   ;
 
 fragment Exp
@@ -103,30 +91,112 @@ fragment Number
   )
   ;
 
-fragment WSorComment
-  : (WS | Comment)*
+fragment Gt   : '>';
+
+fragment NthFunctions
+  : 'nth-child'
+  | 'nth-last-child'
+  | 'nth-of-type'
+  | 'nth-last-of-type'
   ;
+/**
+ * TOKENS
+ *  - default mode should look for selectors and at-rule starts
+ *  - selector mode should look for selectors and '{'
+ *  - at-rule mode should look for any token and blocks and outer '{'
+ *  - declaration list mode should look for idents and at-rule starts and selectors (nesting)
+ *  - declaration mode should look for valid value tokens and ';'
+ *  - custom property mode should look for any token and blocks and outer ';'
+ */
 
-fragment Gt   : '>';
+/** 
+ * Uses nongreedy wildcard
+ * @see https://github.com/antlr/antlr4/blob/master/doc/wildcard.md
+ */
+Comment     : '/*' .*? '*/' -> skip;
 
-CompareOp   : (Gt | '<') '='?;
+/**
+ * Aliased because Less will not skip CSS comments
+ *   e.g. (Whitespace | Comment)
+ */
+WS          : Whitespace;
+Comma       : ',';
+String      : DoubleString | SingleString;
 LCurly      : '{';
 RCurly      : '}';
 LParen      : '(';
 RParen      : ')';
 LSquare     : '[';
 RSquare     : ']';
+
+/**
+ * CSS syntax says we should identify integers as separate from numbers,
+ * probably because there are parts of the syntax where one is allowed but not the other?
+ */
+UnitlessNum     : Number;
+UnsignedInt     : Digit+;
+SignedInt       : Integer;
+
+/** Simple Selectors */
+Star        : '*' -> mode(Selector);
+Ampersand   : '&' -> mode(Selector);
+ID          : '#' Ident -> mode(Selector);
+Class       : '.' Ident -> mode(Selector);
+Element     : Ident -> mode(Selector);
+
+NthSyntax   : 'odd' | 'even' | Integer | Integer? [nN] (WS* [+-] WS* Digit)?;
+NthChild    : ':' NthFunctions '(' WS* NthSyntax WS* ')';
+Pseudo      : ':' ':'? Ident ('(' .*? ')')? -> mode(Selector);
+/** @todo - lookup */
+Attribute   : LSquare WS* Ident ('=') WS* (Ident | String) WS* () RSquare -> mode(Selector);
+
+
+mode Selector;
+Selector_WS       : WS -> type(WS);
+Selector_Comma    : Comma -> type(Comma);
+
+Selector_ID       : ID -> type(ID);
+Selector_Class    : Class -> type(Class);
+Selector_Element  : Element -> type(Element);
+Selector_Pseudo   : Pseudo -> type(Pseudo);
+Selector_Star     : Star -> type(Star);
+Selector_Amp      : Ampersand -> type(Ampersand);
+Selector_Attribute: Attribute -> type(Attribute);
+Selector_LCurly   : LCurly -> type(LCurly), pushMode(DeclarationList);
+
+mode DeclarationList;
+
+
+ColorIdentStart : '#' [a-f];
+
+CompareOp   : (Gt | '<') '='?;
+
 Semi        : ';';
+Colon       : ':';
+PropAssign  : Colon;
 
 Plus : '+';
 Minus       : '-';
-Comma       : ',';
 Divide      : '/';
 Eq          : '=';
-Star        : '*';
 Tilde       : '~';
+/** a namespace or column combinator */
+Pipe        : '|';
+
+Combinator  : Plus | Gt | Tilde | Pipe;
+AttrMatch   : [*~|^$] '=';
+PlainIdent  : Ident;
+CustomProp  : '--' Ident;
+
+Cdo         : '<!--' -> skip;
+Cdc         : '-->' -> skip;
+
+/** Ignore BOM */
+UnicodeBOM  : '\uFFFE' -> skip;
+
+AttrFlag    : [is];
+Function    : Ident '(';
 
-Combinator  : Plus | Gt | Tilde;