Mixing generateStubs with java and xtend files

My understanding is that in .mwe2 files code { preferXtendStubs = } controls whether .java or .xtend files should be generated. If the destination .xtend or .java file exists, it is not overwritten, otherwise a stub file is created.

Sometimes some people think that some files should be in .java and others in .xtend, e.g. …serializer/SemanticSequencer.xtend and serializer/…SyntacticSequencer.java . The problem report is that in such cases it is not possible to prevent the generation of serializer/…SyntacticSequencer.xtend, if serializer/…SyntacticSequencer.java does exist. And if both files coexist at the end the compilation does not work. So:

• when generating stubs in Xtend, avoid creating files, if the same filename but with extension .java exists.
• when generating stubs in Java, avoid creating files, if the same filename but with extension .xtend exists.

Start by tracing the generateStubs behavior controlled by preferXtendStubs in the .mwe2 configuration. Check the existing stub-generation tests, if present, and verify that generation skips a .xtend file when the matching .java file exists, and vice versa.