Update element-transformer to discover properties added by middleware. At the moment for theme and i18n etc the author still needs to remember to extend the widgets properties just to ensure that they element-transformer picks them up.
Did a few tests and I was unable to reproduce this. I'll keep this open in case there is something I'm missing. I created a PR to remove the extraneous extends from the functional widgets in @dojo/widgets.
Update
element-transformer
to discover properties added by middleware. At the moment for theme and i18n etc the author still needs to remember to extend the widgets properties just to ensure that they element-transformer picks them up.