Hi,
-----incquery-dev-bounces@xxxxxxxxxxx ezt írta: ------The derived feature spec: the current language of Xcore does not
allow to write something like
'derived Int numberOfBooks spec library.numberOfBooksOfWriter'. The
problem is with the spec keyword. If I create an other language (for
example 'IncQueryXcore' which extends the Xcore language) then I can
create a new language element XIncQueryDerivedFeature, which has a
definition like:
XIncQueryDerivedFeature:
{XIncQueryDerivedFeature}
'incquery-derived'
type=XGenericType multiplicity=XMultiplicity?
name=ID
'spec' (pattern=[patternLanguage::Pattern])
(';')?
;
Here, note that the keyword is 'incquery-derived', not 'derived'.
Using the latter keyword would cause that the antlr generator throws
an error that the given language is not LL(*), because an
XStructuralFeature (from Xcore) can also start with the 'derived'
keyword.
So if we used there 'derived', that would be a keyword clash between the two separate rules XIncQueryDerivedFeature and XStructuralFeature.
But do they absolutely need to be two separate rules? Can't we just change the rule XStructuralFeature by adding an _optional_ tail looking like this:
('spec' (pattern=[patternLanguage::Pattern]))?
And then there would be only XStructuralFeatures, some of which would have a "spec" clause. So it seems to me that it is possible to keep the simpler syntax.
Of course, this solution may mean that we would have to add a validator rule to enforce that if the feature has a spec, then it must be marked as derived as well. Then again, incquery-based derived features will require a buttload of other validators as well.
Disclaimer: I am far from being an Xtext expert, so forgive me if I have said something stupid :)
Cheers
Gábor
