[antlr-interest] ANTLR - Detecting if parsing was successful

[Ron Hunter-Duvar]

Hi Kunal,

There's a getNumberOfSyntaxErrors() method available on the parser 
object. If there were any errors this will return a number greater than 
zero (though I don't believe it includes lexer errors, you have to check 
separately for them). You can test this when the parsing finishes.

To detect at the end of individual rules, you can test the state.failed 
field. But just looking at the generated code, I don't think testing it 
in the @after will work, because a match failure will result in an early 
return, so the @after won't get executed. I don't know if there's a way 
to tell Antlr to put your code in the finally block to guarantee it 
always gets executed (and if so, you'd probably want to check 
state.backtracking to see if this is a real failure or a failure during 
backtracking). Otherwise, I think you'd need to check in an action in 
the calling rule (but then that action won't be executed until the 
calling rule succeeds). I'm not sure if there's a way to make this work.

Turning off recovery is a separate issue. I don't know if there's any 
other way than overriding the recover method and possibly some related 
methods in BaseRecognizer.

Ron


Kunal Sawlani wrote:
> Hi,
> I am a new to ANTLR and have been trying to detect if the parsing was
> successful or not. As of now, I was using the @after block, which gets
> executed
> only if the parsing was successful. But this block gets executed, even for
> incorrect inputs in the language. I think I am missing something, which I
> must do
> to deactivate the error recovery mechanism, to avoid the after block from
> being executed. Can anyone please guide me to some material on this issue.
>
> Any help would be greatly appreciated.
> Thanks
>   

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Ron Hunter-Duvar | Software Developer V | 403-272-6580
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