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Complete keyword with lookahead [message #828096]

Sat, 24 March 2012 03:23

Eclipse User

Hi!

If one of the next grammar elements of a content assist context is a special keyword how can I propose at this context what follows after the keyword (without hacking the grammar with a special datatype)? For example, if the grammar snippet looks like

IndexedType: "[" ind=[Index] "]"

where "[" is keyword, I want to show up at the context offset before "[" not only the keyword "[", but also the whole completion rule, like "[i]" as a proposal. The problem is, that the complete* and complete_* rules are not called at at context of a keyword, which has no feature assigned to it.
The easiest way would be to override completeKeyword and call completeIndexedType_Ind which itself needs a non-null Assignment object, and I don't know where to get it from. Is there a better method to concatenate following proposals?

Best regards,
Alex.

Re: Complete keyword with lookahead [message #828103 is a reply to message #828096]

Sat, 24 March 2012 03:42

Eclipse User

Hi,

one option is to provide a template proposal for that. You can try them out using the Xtext editor's preference page, export them and provide them along with the editor.
This is is covered in the documentation as well as some blog posts.

Alex

Re: Complete keyword with lookahead [message #828125 is a reply to message #828103]

Sat, 24 March 2012 04:30

Eclipse User

A template is a nice idea, thank you for the hint. But I don't think its the correct feature for me in this context. I want to look at the token "[i]" as a whole name and not providing a template of the form "'[' ... ']'".
Sure I can write a grammar like

IndexedType: ind=[Index | PrefixedID] "]"
PrefixedID: "[" ID;

and change the corresponding qualified name in order to use default XText features. But that's a sort of hack in the grammar.

So far I have overwritten completeKeyword which itself doesn't call lookUpCrossReferences but imitates this by manually calling the scope provider for objects of type Index. After that I call ICompletionAcceptor with changed ICompletionProposals.
But somehow I think that this way is a sort of hacky as well, since I have to overwrite the completeKeyword method. Eventually there might be for this kind of proposals ("concatenation" of proposals with lookahead) some corresponding API methods, but I haven't found any of these, since when calling the proposal provider before a keyword, I think, the only complete method which is called is completeKeyword.

[Updated on: Sat, 24 March 2012 04:31] by Moderator

Re: Complete keyword with lookahead [message #828472 is a reply to message #828096]

Sat, 24 March 2012 17:40

Eclipse User

Hi Alex,

you can obtain the assignment from the YourDslGrammarAccess.
Instead of completeKeyword I'd try to specialize the complete_IndexType
implementation.

Regards,
Sebastian
--
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Go visit: http://xtext.itemis.com

Am 24.03.12 03:23, schrieb Alex G:
> Hi!
>
> If one of the next grammar elements of a content assist context is a
> special keyword how can I propose at this context what follows after the
> keyword (without hacking the grammar with a special datatype)? For
> example, if the grammar snippet looks like
>
> IndexedType: "[" ind=[Index] "]"
>
> where "[" is keyword, I want to show up at the context offset before "["
> not only the keyword "[", but also the whole completion rule, like "[i]"
> as a proposal. The problem is, that the complete* and complete_* rules
> are not called at at context of a keyword, which has no feature assigned
> to it.
> The easiest way would be to override completeKeyword and call
> completeIndexedType_Ind which itself needs a non-null Assignment object,
> and I don't know where to get it from. Is there a better method to
> concatenate following proposals?
>
> Best regards,
> Alex.

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