[antlr-interest] How to throw an exception for all parsing errors?

[Johannes Luber]

Peter C. Chapin schrieb:
> Hello!
> 
> I'm working with the C# target. I'm writing test cases for my parser. I
> try to parse a collection of input files to verify that they all parse as
> expected (later I'll probably also verify that erronous input fails to
> parse, but that's for another day). I'm trying to use NUnit to manage the
> test cases.
> 
> It is convenient for the parser to throw an exception at the first problem
> since NUnit will catch unhandled exceptions and display their tracebacks,
> etc. The ANTLR book talks about how to do this. As I understand it I have
> to provide my own mismatch() and recoverFromMismatchedSet() methods. I
> also have to provide a @rulecatch block that catches RecognitionException
> and rethrows it. The book shows this in Java, but the C# version is
> basically the same (I replaced IntStream with IIntStream).
> 
> It almost seems to work. However while playing with my test cases I
> noticed that under certain circumstances no exception is thrown and the
> parser returns normally... even though an error message is written to
> standard error. In the case in question I have an extra ';' where 'END' is
> supposed to be. I get the following message on standard error:
> 
> extraneous input ';' expecting END
> 
> The message is quite reasonable. The problem is that NUnit thinks the test
> succeeded. NUnit's GUI console does display the error message on the
> 'Console Error' tab but the test still shows green. This is a problem for
> me because when I run my tests I want to be able to just look at the green
> lights and be happy. If I also have to investigate other tabs I will
> likely forget and I might overlook a problem.
> 
> So my question is simply: is there a way to get even this kind of error to
> thrown an exception as well? I could also solve my problem if there was
> some way to learn from the result returned by the parser if the parse was
> completely successful or not. Did ANTLR execute any kind of recovery? If I
> could check for that I could fail the test and be happy as well.
> 
> Peter

This seems to be a bug in ANTLR as such behavior doesn't fit my
expectations, too. But it seems to be more likely that this is a general
target bug and not specific to the C# target. Without the grammar in
question neither Ter nor me can be sure. Can you send it on- or off-list
to both of us? Does your grammar depend on C#-code to work correctly or
can it easily converted to Java to cross-check the cause?

Johannes
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