Accessing .objects on variable typed type[Model] gives error: type[Model]" has no attribute "objects"

[richardebeling]

After updating django-stubs from 4.2.3 to 4.2.4, this code:

from django.db.models import Model

def test(SomeModel: type[Model]):
    SomeModel.objects.all()

produces this output when running mypy test.py:

test.py:4: error: "type[Model]" has no attribute "objects"  [attr-defined]

It passed typechecking with 4.2.3. According to django's documentation on Model attributes, objects should be accessible on models unless the model has a custom manager.

The release notes for 4.2.4 don't indicate to me that this was changed. Was this change intentional? If yes, how should I annotate test above to make clear that it expects some model class with the default objects manager attribute?

System information

• OS: ubuntu 22.04
• python version: 3.10.12
• django version: 4.2.3
• mypy version: 1.4.1
• django-stubs version: 4.2.4
• django-stubs-ext version: 4.2.2

[flaeppe]

Duplicate of #1684

[richardebeling]

Ah, thanks. I'd argue the release notes should mention this as a possibly breaking change, since code that passed type checking before now fails. django-stubs 4.2.4 has this bullet point in the release notes:

We also update our stubs to be compatible with Django 4.2.5 (and all prior versions of 4.2).

but django doesn't seem to have changed their policy regarding .objects in the 4.1 -> 4.2 update, so imho the bullet point doesn't "justify" higher strictness regarding .objects on models.

What do you think?

[flaeppe]

Yeah maybe we should've been more clear in the release notes.

I think the bullet point aims for all prior 4.x versions of Django, not django-stubs? Not sure I follow otherwise

I'd argue that this improved alignment with the runtime justifies a breaking change. I'd say the new version just found a bug.

And I don't think the behavior regarding objects is anything new for the 4.x series. But perhaps we've found an ambiguity in the Django documentation?

[richardebeling]

I see how my last post was a bit ambiguous, I edited it to make it a bit clearer.

In the end, I'm only suggesting to add an additional bullet point in the release notes, something along the lines of:

• We no longer assume the objects attribute to be present on generic Model classes. As per the django documentation, code working with generic models should use the _default_manager attribute instead.

[sobolevn]

Done!