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Embedding ANTLR3 Island Parser in Xtext [message #1765462]

Fri, 09 June 2017 19:16

Justin Szaday

Messages: 2
Registered: June 2017

Junior Member

I am working on converting a grammar from ANTLR3 to Xtext. The ANTLR3 grammar uses an 'island parser' for a certain rule, I will refer to them as CustomLexer and customRule. In ANTLR3, this looks like:

customRule
  @init { CommonTree custom = null; }
  : PREFIX { custom = invokeCustomLexer(); } -> ^( {custom} )
  ;

Where invokeCustomLexer() is a function that invokes the CustomLexer at the current position in the stream and then shifts the stream to the position it returns after it completes.

It does not seem like there is a good way to convert this rule to Xtext since it does not appear to support inline ANTLR. Is there a way I can either have an automated task append this rule to the or otherwise append/embed this code in/to the generated ANTLR? Any help here would be greatly appreciated.

Yes, island parsers are bad and I do not like them whatsoever but given the structure of the language and the need for legacy support, there is simply no way around using one in this context.

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