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Configuring Scope Provider Error Handler [message #759778]

Wed, 30 November 2011 00:44

Mirko Raner

Messages: 125
Registered: July 2009
Location: New York City, NY

Senior Member

Hi all,

we're trying to debug some tricky scope provider issues and we just noticed that a number of exceptions get silently swallowed because AbstractDeclarativeScopeProvider by default uses a NullErrorHandler. So, we're trying to bind to the following injection point in ADSP:

	@Inject(optional=true)
	@Named(NAMED_ERROR_HANDLER)
	private PolymorphicDispatcher.ErrorHandler<IScope> errorHandler = new PolymorphicDispatcher.NullErrorHandler<IScope>();

Our configure method looks like this, but it's not working (it does get executed, though):

binder.bind(
		((TypeLiteral<PolymorphicDispatcher.ErrorHandler<IScope>>)TypeLiteral.get(Types.newParameterizedType(PolymorphicDispatcher.ErrorHandler.class, IScope.class)))).
				annotatedWith(Names.named(AbstractDeclarativeScopeProvider.NAMED_ERROR_HANDLER)).
				toInstance(new PolymorphicDispatcher.DefaultErrorHandler<IScope>());

When we break in the debugger in our custom scope provider it still shows a NullErrorHandler as the error handler, so apparently the binding didn't take. We configure the binding in the runtime module that goes with our scope provider, but maybe that's too late?
Any idea what we're doing wrong here?

Thanks!

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Re: Configuring Scope Provider Error Handler [message #759810 is a reply to message #759778]

Wed, 30 November 2011 07:43

Sebastian Zarnekow

Messages: 3118
Registered: July 2009

Senior Member

Mirko,

did you try to bind the error handler as a class instead of the type?
bind(ErrorHandler.class).anoatedWith(...).to(..);

Regards,
Sebastian
--
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Am 30.11.11 01:45, schrieb Mirko Raner:
> Hi all,
>
> we're trying to debug some tricky scope provider issues and we just
> noticed that a number of exceptions get silently swallowed because
> AbstractDeclarativeScopeProvider by default uses a NullErrorHandler. So,
> we're trying to bind to the following injection point in ADSP:
>
> @Inject(optional=true)
> @Named(NAMED_ERROR_HANDLER)
> private PolymorphicDispatcher.ErrorHandler<IScope> errorHandler = new
> PolymorphicDispatcher.NullErrorHandler<IScope>();
> Our configure method looks like this, but it's not working (it does get
> executed, though):
>
> binder.bind(
> ((TypeLiteral<PolymorphicDispatcher.ErrorHandler<IScope>>)TypeLiteral.get(Types.newParameterizedType(PolymorphicDispatcher.ErrorHandler.class,
> IScope.class)))).
> annotatedWith(Names.named(AbstractDeclarativeScopeProvider.NAMED_ERROR_HANDLER)).
>
> toInstance(new PolymorphicDispatcher.DefaultErrorHandler<IScope>());
> When we break in the debugger in our custom scope provider it still
> shows a NullErrorHandler as the error handler, so apparently the binding
> didn't take. We configure the binding in the runtime module that goes
> with our scope provider, but maybe that's too late?
> Any idea what we're doing wrong here?
> Thanks!
>

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Re: Configuring Scope Provider Error Handler [message #897735 is a reply to message #759810]

Wed, 25 July 2012 07:51

Sebastian Zarnekow

Messages: 3118
Registered: July 2009

Senior Member

For the sake of completeness: This one will do the trick:

public void configureErrorHandler(Binder binder) {
		binder.bind(new TypeLiteral<PolymorphicDispatcher.ErrorHandler<IScope>>() {}).annotatedWith(
				Names.named(AbstractDeclarativeScopeProvider.NAMED_ERROR_HANDLER)).to(MyErrorHandler.class);
	}
	
	static class MyErrorHandler extends PolymorphicDispatcher.DefaultErrorHandler<IScope> {
		public MyErrorHandler() {
			System.out.println("initialized custom error handler");
		}
	}

[Updated on: Wed, 25 July 2012 07:52]

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Re: Configuring Scope Provider Error Handler [message #897765 is a reply to message #759810]

Wed, 25 July 2012 08:39

Aaron Digulla

Messages: 258
Registered: July 2009
Location: Switzerland

Senior Member

To bind this in Xtext 2.3.0, use this code:

    public void configureErrorHandler(Binder binder) {
        Logger logger = Logger.getLogger(PolymorphicDispatcher.class);
        PolymorphicDispatcher.ErrorHandler<IScope> handler = PolymorphicDispatcher.WarningErrorHandler.get( logger );
        
        binder.bind(new TypeLiteral<PolymorphicDispatcher.ErrorHandler<IScope>>(){})
        .annotatedWith(Names.named(AbstractDeclarativeScopeProvider.NAMED_ERROR_HANDLER))
        .toInstance( handler )
        ;
    }

but there is a catch: You will get many exceptions of type NoSuchMethodException. To fix that, use this error handler:

import org.apache.log4j.Logger;
import org.eclipse.xtext.util.PolymorphicDispatcher.ErrorHandler;

public class PolymorphicDispatcherErrorHandler<RT> implements ErrorHandler<RT> {

    private Logger logger;

    public PolymorphicDispatcherErrorHandler( Logger logger ) {
        this.logger = logger;
    }
    
    @Override
    public RT handle( Object[] params, Throwable throwable ) {
        
        if( !(throwable instanceof NoSuchMethodException ) ) {
            logger.warn("Error in polymorphic dispatcher : "+throwable.getMessage(), throwable);
        }
        
        return null;
    }

    
}

Replace "PolymorphicDispatcher.WarningErrorHandler.get" with "new PolymorphicDispatcherErrorHandler<IScope>" to use it.

Regards,

A. Digulla

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Re: Configuring Scope Provider Error Handler [message #1062776 is a reply to message #897765]

Mon, 10 June 2013 17:06

Michael Vorburger

Messages: 103
Registered: July 2009

Senior Member

Thank you for this post - very useful. Q: Is there any particular reason something like this WarningErrorHandlerWithoutNoSuchMethodException is not used by default in the AbstractDeclarativeScopeProvider instead of the current NullErrorHandler? That would make finding some problems in your own ScopeProvider easier out-of-the-box - without having to apply this. Bugzilla?

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Re: Configuring Scope Provider Error Handler [message #1063878 is a reply to message #1062776]

Fri, 14 June 2013 16:40

Aaron Digulla

Messages: 258
Registered: July 2009
Location: Switzerland

Senior Member

My feeling is that the code is designed to fail silently in production. Unfortunately, this makes development of Xtext DSLs harder than it needs to be.

I would like to see a "development mode" for DSLs where these are disabled. If you like the idea, raise your voice: https://bugs.eclipse.org/bugs/show_bug.cgi?id=407874

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