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Rules regarding CrossReferences [message #990074]

Mon, 10 December 2012 13:04

Robert Wild
Messages: 26
Registered: August 2012

Junior Member

Given this simple example:

Class:
	"class" name=ID ("extends" parent=[Class])?
;

What's the best way to implement basic rules regarding the crossReference in parent=[Class]. Rules like no self-reference and no cycles.

I know of two possibilities:
1. I could define these rules in a custom validator, but then a custom ProposalProvider is necessary, too. One Rule has to be implemented in two places.

2. Or I could use a custom ScopingProvider, but then I cannot provide meaningful error messages. It would always say "reference not found" which isn't helping a lot.

Is there some other way?

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Re: Rules regarding CrossReferences [message #990077 is a reply to message #990074]

Mon, 10 December 2012 13:34

Henrik Lindberg
Messages: 2429
Registered: July 2009

Senior Member

On 2012-10-12 19:04, Robert Wild wrote:
> Given this simple example:
>
> Class:
> "class" name=ID ("extends" parent=[Class])?
> ;
>
>
> What's the best way to implement basic rules regarding the
> crossReference in parent=[Class]. Rules like no self-reference and no
> cycles.
>
> I know of two possibilities:
> 1. I could define these rules in a custom validator, but then a custom
> ProposalProvider is necessary, too. One Rule has to be implemented in
> two places.
>
> 2. Or I could use a custom ScopingProvider, but then I cannot provide
> meaningful error messages. It would always say "reference not found"
> which isn't helping a lot.
>
> Is there some other way?
Custom linker; that runs after the default linking. Extend the
LazyLinker and implement afterModelLinked. You can look at my
implementation (PPLinker) in cloudsmith / geppetto @ github.

In your custom linker just validate links and issue errors.
- henrik

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Re: Rules regarding CrossReferences [message #990220 is a reply to message #990074]

Tue, 11 December 2012 08:26

Robert Wild
Messages: 26
Registered: August 2012

Junior Member

does that prevent items from being displayed by the ProposalProvider?

I haven't tried it yet, but as far as I've understood it, it doesn't seem like it does things differently than validation does, except it's organized a bit different.

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Re: Rules regarding CrossReferences [message #990227 is a reply to message #990220]

Tue, 11 December 2012 08:51

Sebastian Zarnekow
Messages: 2788
Registered: July 2009

Senior Member

Am 11.12.12 14:26, schrieb Robert Wild:
> does that prevent items from being displayed by the ProposalProvider?
> I haven't tried it yet, but as far as I've understood it, it doesn't
> seem like it does things differently than validation does, except it's
> organized a bit different.
>

Custom ContentAssist and custom validation is the way to go, e.g.
sometimes you want to show invalid proposals if there are no others
available but still issue an error + quickfix for that particular reference.

Regards,
Sebastian
--
Looking for professional support for Xtext, Xtend or Eclipse Modeling?
Go visit: http://xtext.itemis.com

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Re: Rules regarding CrossReferences [message #990233 is a reply to message #990227]

Tue, 11 December 2012 09:18

Robert Wild
Messages: 26
Registered: August 2012

Junior Member

So there's no easy way to prevent the redundancy of rules in ContentAssist and validation?

I guess I can implement a method for checking a rule and call it from contentAssist and validation thus eliminating redundancy.

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