ANTLR: exclude (skip) tokens when building AST tree

Question

Given the following grammar (in ANTLR v3):

test : value0 COMMA_KEYWORD value1 (COMMA_KEYWORD value2)*;

How can we exclude (skip) COMMA_KEYWORD from the AST tree built by ANTLR (and without using a write rule)?

Answer 1

The alternative to using rewrite rules is to use tree construction operators:

https://theantlrguy.atlassian.net/wiki/spaces/ANTLR3/pages/2687090/Tree+construction

You can use ! operator to omit a token or subtree from AST:

test : value0 COMMA_KEYWORD! value1 (COMMA_KEYWORD! value2)*;