"It turns out that the MEF that you ship works just fine with MEF provided
you provide your own MetadataView implementation. The metadata view
implementation is registered with the [MetadataViewImplementation()]
attribute. This is exactly what we did with our custom implementation a
while ago and it looks like it is now officially supported. You might
want to add this information to your FAQs and the github comments. Also,
it would be nice if you changed the exception to indicate that you have to
provide a valid implementation and register with the attribute instead of
saying that the metadata view was invalid."
We haven't written the documentation of note / or a test showing the bad behavior. This bug is just a reminder to go do so at a point in the future. When I fix it i'll note how to verify my fix.