Upgrade to Mypy 1.0

[christianbundy]

I have made things!

Upgrade to Mypy 1.0

Related issues

Refs python/mypy#13685

Closes #340

[intgr]

Approved CI run.

[intgr]

Some if not all of the typecheck errors are due to upstream changes in DRF test suite, not from upgrading mypy.

[christianbundy]

Do we just add them as excluded errors in ./scripts/typecheck_tests.py? Trying to make sure I understand the procedure.

[intgr]

Do we just add them as excluded errors in ./scripts/typecheck_tests.py?

I've looked at each error, and checked if it's something we're missing in stubs or a false positive. Usually it's a false positive, or some new feature that has been merged in DRF but will be in the next version (e.g. #338).

But it's annoying and confusing, especially for new contributors, when CI checks start to fail due to unrelated changes. So I've been thinking that we may want to freeze the git commit hash that we check (like is already done in django-stubs).

But the downside is that then we would have to periodically update this hash, something that's been a bit neglected in django-stubs.

[intgr]

I rebased your branch. The remaining CI errors are from mypy 1.0 update.

[christianbundy]

Thanks! For convenience, here are the relevant files:

• https://github.com/encode/django-rest-framework/blob/22d206c1e0dbc03840c4d190f7eda537c0f2010a/tests/test_permissions.py
• https://github.com/encode/django-rest-framework/blob/22d206c1e0dbc03840c4d190f7eda537c0f2010a/tests/test_versioning.py

Problem 1

drf_source/tests/test_permissions.py:593: error: "<typing special form>" not callable
drf_source/tests/test_permissions.py:599: error: "<typing special form>" not callable
drf_source/tests/test_permissions.py:653: error: "<typing special form>" not callable
drf_source/tests/test_permissions.py:661: error: <nothing> not callable
drf_source/tests/test_permissions.py:673: error: "<typing special form>" not callable
drf_source/tests/test_permissions.py:681: error: <nothing> not callable
drf_source/tests/test_permissions.py:736: error: "<typing special form>" not callable

These seem to be exclusively complaining about this pattern:

composed_perm = permissions.IsAuthenticated | permissions.AllowAny
assert composed_perm().has_permission(request, None) is True

This only happens when you __or__ permissions, and it looks like __and__ is unaffected.

I don't really understand why this would happen, since the stub definition seems to treat | and & similarly, but I'm inclined to think that maybe this is a bug in Mypy where | is being treated as a type union. What do you think?

Problem 2

drf_source/tests/test_versioning.py:28: error: "None" not callable
drf_source/tests/test_versioning.py:35: error: "None" not callable
drf_source/tests/test_versioning.py:43: error: "None" not callable
drf_source/tests/test_versioning.py:50: error: "None" not callable

These are all coming from:

self.versioning_class()

Where self is a subclass of APIView with a get() method defined.

The stub defines this as nullable, and DRF source seems to agree that this is possible, so I can add an ignore for this one.

[intgr]

I don't really understand why this would happen, since the stub definition seems to treat | and & similarly, but I'm inclined to think that maybe this is a bug in Mypy where | is being treated as a type union. What do you think?

Yes indeed, mypy thinks composed_perm is a type alias with Union. For now, an ignore is fine.

I always hated how DRF requires permissions checks to be classes, not instances.

This can cause problems in actual user code. Maybe report a mypy bug? Mypy could look at whether a class overrides the __or__ method, or look at the method's return value, to detect this. (Does it matter that this comes from the metaclass?)

[intgr]

There are still some test failures. Sorry, I could have approved the CI run earlier.

[christianbundy]

Done! And I ran act locally and it looks like it passed all tests. (Though I'd love to be able to run CI without approvals if that's easy to fix.)

[flaeppe]

Done! And I ran act locally and it looks like it passed all tests. (Though I'd love to be able to run CI without approvals if that's easy to fix.)

I've approved the CI run. You shouldn't need approvals once you've become a contributor.

[intgr]

Thanks!