FYI MyPy 0.90 came out today with a big breaking change that it no longer includes typeshed for 3rd party requirements. You now need to install dedicated type stub libraries This greatly amplifies the need for an idea proposed by a user last month:

stubs_mapping

. Whereas we normally don't allow >2 targets to refer to the same module for dep inference, we would if one is a type stub (we already do this for first party stubs). I think we should probably cherry-pick to 2.5, possibly even 2.4? Without this, MyPy 0.90 is not very practical with Pants because you have to manually add deps on all relevant type stubs