mypy.ini module-specific override doesn't work without __init__.py

[JelleZijlstra]

In the following layout:

• mypy.ini contains

[mypy]
disallow_untyped_defs = True

[mypy-a.b.*]
disallow_untyped_defs = False

• a contains __init__.py and a directory a/b
• a/b contains c.py with an untyped def

Mypy will complain about missing type annotations in a.b.c. If I create a/b/__init__.py, the errors go away. This is a regression in v0.800.

[hauntsaninja]

Are you using --namespace-packages? (It's probably not a regression as much as mypy previously just didn't check c.py)

[JelleZijlstra]

I'm not using --namespace-packages. I think you're right that the file was not checked before, so this is not so much as a regression as a pre-existing bug that got exposed by recent changes.

[hauntsaninja]

You'll need to use --namespace-packages for mypy to treat a/b/c.py as a.b.c instead of c. Alternatively, you can add __init__.py to a/b.

[hauntsaninja]

So I don't think that there is a bug here, although mypy should make --namespace-packages the default (#9636)