[antlr-interest] Help with a parser

[Scott Smith]

I assume this is the proper place to put this.  I'm trying to build a parser for filters generated by SOLR (lucene.apache.org).

Examples of valid "sentences" the parser should parse are:

fq = fred

fq = (fred OR bill)

fq = harry:(fred OR bill)

fq = (harry:fred OR jack:bill)

fq = ((harry:fred OR bill) AND (jane OR marry:sally))

terms can be nested to arbitrary levels.  The colon really binds to the word before it (e.g., "harry:").

I've listed the parser below (which doesn't work).  Can someone suggest what I can do?  It seems like a simple problem, but so far I haven't cracked it.  I will admit that I've only been playing with Antlr the last week or so.  I did play all of Scott Stanchfield's excellent videos on vimeo.  But, still I'm confused.

When I run the parser in antlrworks with example 3 ("fq = harry:(fred OR bill)" - no quote marks), it finds "fq = harry:(fred" and then it wants the right paren instead of expanding out the filter_expr rule.  What am I missing?

Thanks

Scott

Here's the parser.

grammar testGrammer;

options {
  language = Java;
}

@header {
  package a.b.c;
}

@lexer::header {
  package a.b.c;
}

filter:
  'fq' '=' filter_expr EOF
  ;

term
  : KEYWORD
  | STRING
  | '(' filter_expr ')'
  ;

fieldname
     :    FIELDNAME? term
     ;


filter_expr:
  fieldname (((AND | OR | NOT))? fieldname)*
  ;

FIELDNAME
     :    KEYWORD ':' ;

AND : 'AND' | '&&' ;
OR  : 'OR' | '||' ;
NOT : 'NOT' | '!' ;
KEYWORD : LETTER (LETTER | NUM_CHAR | '_')*;
STRING : '"' NONCONTROL_CHAR* '"' ;
WS  : ' ' | '\t' | '\n' | '\r' | '\u3000' {$channel=HIDDEN; } ;

fragment NONCONTROL_CHAR: LETTER | NUM_CHAR | SPACE | SYMBOL;
fragment SYMBOL:  ' '..'!' | '#'..'/' | ':'..'@' | '['..'`' | '{'..'~';
fragment LETTER: LOWER | UPPER;
fragment LOWER: 'a'..'z';
fragment UPPER: 'A'..'Z';
fragment NUM_CHAR: '0'..'9';
fragment SPACE: ' ' | '\t';