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Automatic Validation ( NoViableAltException) [message #1016371]

Wed, 06 March 2013 09:33

junior developer

Messages: 354
Registered: January 2013

Senior Member

Hi all,

I can't understand NoViableAltException .Which situations getting this error.

Default error message for this exception :no viable alternative at input 'datatype'

Best Regards

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Re: Automatic Validation ( NoViableAltException) [message #1016487 is a reply to message #1016371]

Wed, 06 March 2013 16:29

Christian Dietrich

Messages: 13359
Registered: July 2009

Senior Member

Hi,

this comes from antlr. here is what the antlr4 (xtext uses antlr 3) javadoc says

Indicates that the parser could not decide which of two or more paths to take based upon the remaining input. It tracks the starting token of the offending input and also knows where the parser was in the various paths when the error.

~Christian

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Re: Automatic Validation ( NoViableAltException) [message #1016544 is a reply to message #1016371]

Wed, 06 March 2013 20:35

junior developer

Messages: 354
Registered: January 2013

Senior Member

Hi Christian,

My validation code for this error:
public class MyDsl1SyntaxErrorMessageProvider extends
SyntaxErrorMessageProvider {

@Override
public SyntaxErrorMessage getSyntaxErrorMessage(IParserErrorContext context) {

if (context.getRecognitionException() != null
&& context.getRecognitionException().token != null) {
//for no viable alternative at input 'datatype' error
if (context.getRecognitionException() instanceof NoViableAltException ){
return new SyntaxErrorMessage("?????you must enter string??????? ", null);
}
}
return super.getSyntaxErrorMessage(context);
}
Defined rule my grammar :
Model:
(datatype += DataType)*
&(type += Type)*

DataType returns DataType:
'datatype' name=ID
;
Test1 DSL output :
datatype 3 // if I enter a integer value ,I receive "no viable alternative at input '3'" default error (I changed it own message)
datatype String
datatype int

Test2 DSL output: this In this scenario ,call datatype 6 but I do not an error hence I receive error only datatype 3 .I do not understand why ?

datatype 3 // if I enter a integer value ,I receive "no viable alternative at input '3'" default error (I changed it own message)

datatype 6 //I must receive same error ("you must enter string")this section but ı only receive error first line

datatype int

I hope explain my problem

Best regards

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Re: Automatic Validation ( NoViableAltException) [message #1016551 is a reply to message #1016544]

Wed, 06 March 2013 21:09

Christian Dietrich

Messages: 13359
Registered: July 2009

Senior Member

guess you have to look into the IParserErrorContext to see where you are
as said before in the other topic: your question and needs are very specific so
you may have to digg yourself (e.g. using debugger)
to find a solution since it is not a general problem.

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