Parsing fails on PGN with multiple comments after final move

[gtim]

Thank you again for this stellar package. It seems PGNs with multiple comments after the final move cannot be parsed. The following PGN throws a syntax error on parse:

[Result "*"]

1. d4 Nf6 { comment 1 } { comment 2 } *

As far as I can tell, the PGN is according to the specification. The following parses properly:

[Result "*"]

1. d4 Nf6 { comment 1 } { comment 2 } 2. Bg5 *

If you're interested, I'd be happy to look into the grammar and write a PR.

[shaack]

Hello and thank you for your thoughts. I am not sure if the PGN specification allows multiple comments after a move. It's not only about parsing, but about the data model of cm-pgn, which only expects one comment after a move.

[donkawechico]

@shaack FWIW, the PGN grammar definitely allows for multiple comments on a move.

See Lines 135-151:

REST_OF_LINE_COMMENT
 : ';' ~[\r\n]* -> skip
 ;

BRACE_COMMENT
 : '{' ~'}'* '}' -> skip
 ;

Because of the -> skip action, the lexer completely ignores any tokens with braces or semicolons, which means you can pile multiple occurrences of those tokens onto one and another and the lexer will simply ignore each one.

You can verify by going to http://lab.antlr.org/ and pasting the PGN grammar into the "Parser" tab. Just make sure to click on the "Lexer" tab and clear its contents first.

[shaack]

Okay, in that case, if you have the time to create a PR, feel free to do so. I will merge it, if it works.