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IJvmModelInferrer is being called for a lexically invalid model [message #1435924]

Thu, 02 October 2014 06:25

Alexander Shutyaev

Messages: 4
Registered: July 2009

Junior Member

Hi all!

Here's a short example:

MyDsl.xtext

grammar org.foo.mydsl.MyDsl with org.eclipse.xtext.xbase.Xbase

generate myDsl "http://www.eclipse.org/mydsl/MyDsl"

Model:
	greetings+=Greeting*
	farewells+=Farewell*;

Greeting:
	'Hello' name=ID '!';

Farewell:
	'Goodbye' greeting=[Greeting];

MyDslJvmModelInferrer.xtend

class MyDslJvmModelInferrer extends AbstractModelInferrer {

	@Inject extension JvmTypesBuilder

	def dispatch void infer(Greeting gr, IJvmDeclaredTypeAcceptor acceptor, boolean isPreIndexingPhase) {
		acceptor.accept(gr.toClass(gr.name + 'Greeting'))
	}

	def dispatch void infer(Farewell fw, IJvmDeclaredTypeAcceptor acceptor, boolean isPreIndexingPhase) {
		acceptor.accept(fw.toClass(fw.greeting.name + 'Farewell'))
	}

}

Now if I start typing in editor

Hello world!
Goodbye

then when I hit spacebar after Goodbye I get a NullPointerException (full stacktrace attached). The reason is that although the file contents is not (yet) lexically valid, my IJvmModelInferrer has been called and the following expression:

fw.greeting.name

resulted in a NullPointerException.

Is this the expected behavior?
If yes, is there any way to ensure that IJvmModelInferrer is called only for a lexically valid model?
If there is no such way, what would be the best practice? Validate manually in the beginning of the infer method? How do I call such kind of validation (I assume there should be some generated lexical validator)?

Thanks in advance!

Attachment: full_npe_stacktrace.txt
(Size: 7.18KB, Downloaded 363 times)

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Re: IJvmModelInferrer is being called for a lexically invalid model [message #1435937 is a reply to message #1435924]

Thu, 02 October 2014 06:52

Sebastian Zarnekow

Messages: 3118
Registered: July 2009

Senior Member

Hi Alex,

the model inferrer is always called and your code should be written in a
robust way - which mainly means it should be null-safe. It is important
to do the model inference with broken models, too. Otherwise you'll see
way too many follow up errors that would be distracting thus the
syntactic problems would be mixed up with linking problems and
validation issues.
Generally speaking, you should not guard your model inferrer with smth
like #hasSyntaxErrors.

Best,
Sebastian
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