Xtext: Customizing Error msg by unordered groups - error-handling

Question

I've defined an unordered group and it works like I expected. The only thing I would like to change is the error msg, which appears when an element of an unordered group isn't modelled yet. Is there an easy way to solve this? I tried already custom checks, but there I got an unexpected behaviour.
Following my rule for the unordered group and the error msg:
Element:
(name=ConfigurationName) &
(description=Description)? &
(tool=Tool) &
(model=Model) &
(interfaces=Interfaces)? &
(paramaters=Parameters)? &
(paramfile=ParamFile)?
;
rule ruleElement failed predicate: {getUnorderedGroupHelper().canLeave(grammarAccess.getElementAccess().getUnorderedGroup())}?
I want to change this error msg to something like: "The following elements are required in the configuration:...."

Answer 1

Xtext has a service called SyntaxErrorMessageProvider that is used to reword parser error messages. You have to define your messages on the parser level (so there will be no EMF model to use), but it is possible to get the original error message and the context, traverse it and provide your own error message.
To register this, open the «YourLanguage»RuntimeModule class, and add the following method:
public Class<? extends ISyntaxErrorMessageProvider> bindISyntaxErrorMessageProvider() {
return «YourLanguage»SyntaxErrorMessageProvider.class;
}
where «YourLanguage«SyntaxErrorMessageProvider is a class introduced by you, extending the class SyntaxErrorMessageProvider, where you can implement your custom function.

Answer 2

I works Automatic Validation customize,I create
public class MyDslLanguageSyntaxErrorMessageProvider extends SyntaxErrorMessageProvider {
}
And I Register it in the MyDslRuntimeModule:
public Class bindISyntaxErrorMessageProvider() {
return MyDslLanguageSyntaxErrorMessageProvider.class;}
But my problem is which package is used for this customization.I used org.xtext.example.mydsl.validation package for create java class .Also I do this customization with xtend class.I do not find enough source in the internet :(

Answer 3

You can use Java to write this Custom SyntaxErrorMessageProvider class, but to bind this you can bind in Runtime Module class. Also u can use any package to declare this class but declaring this class in same package where u have Runtime class makes sense