dzhlobo / mypy-cache-issue-demo

This is a demo of the seems like cache bug of mypy.

The issue is that in particular configuration of packages and files and imports mypy doesn't report a type issue when it previously type-checked the file and the check was correct.

You can see the list of steps to reproduce in bin/test. Shortly it is this:

1. mypy -p main -p src fails because src.lib.protocols.connection.Connection contains the not_exists property while src.app.APIConnection does not have it.
2. We remove this property from protocol, run mypy (it will succeed), and then we return this not_exists property back.
3. mypy -p main -p src would succeed while it is expected to fail as on step 1.

Run:

bin/setup
bin/test