Create a 'generateSources' task that performs all generation tasks

Correct.

+1 good idea, this way one can re-generate all the generated source with a single target. Might make the build also easier to understand.

Well, regenerateSources is another idea altogether. generateSources would not "clean" first and given Gradle's up-to-date checking, would therefore probably not happen.

Little nervous about generateSources and generateTestJpaMetamodelClasses. Most generateSources operate on production sources, whereas generateTestJpaMetamodelClasses operates on test classes.

Little nervous about generateSources and generateTestJpaMetamodelClasses. Most generateSources operate on production sources, whereas generateTestJpaMetamodelClasses operates on test classes.

I think it is ok to combine them under generateSources. I guess the alternative is to have a generateTestSources as well.

Btw, I did not expect the generateSources would clean first by default.