[mdt-ocl.dev] Xtext to LPG

[Ed Willink <ed@xxxxxxxxxxxxx>]

Hi

I made a relatively small Xtext grammar change and suddenly got stupid 
syntax errors, probably because a magic backtracking precedence flipped. 
I therefore started updating the 'equivalent' LPG grammar to look for a 
conflict and realized that the time had come to look at automated Xtext 
to LPG conversion; it's relatively easy.

I've therefore developed/am developing a Tx cascade
QVTo: *.xtext -> *.xtext.XBNF to get a fully referential EBNF model from 
the Xtext CST
QVTo: *.xtext.XBNF -> *.xtext.normal.XBNF to convert to a disjunct of 
conjuncts BNF
QVTo: *.normal.XBNF -> *.inline.XBNF to re-inline non-recursive 
references that were originally from a single rule
Acceleo: *.inline.XBNF -> *.g, *.gi

(XBNF is Xtext BNF, i.e BNF with model annotations)

Currently plausible KWLexer and Parser grammars are generated, Lexer 
still todo; the Xtext and LPG styles are very different.

Action code still to do; should be easy with all the model annotations.

Unfortunately there is no QVTo standalone support so I also had to 
develop that and the corresponding MWE integration.

The build scripts are in the build plugin. The transformations in the 
examples.xtext2lpg plugin.

Since only the build plugin has QVTo dependencies and neither of the 
above plugins are in the Tools build, I don';t think that there is any 
releng impact.

    Regards

        Ed Willink