Type Annotation Errors in Models Inheriting from 3rd Party Packages

[Dresdn]

Bug report

What's wrong

With the latest django-stubs v5.0.4, I've noticed strange behavior when using models that inherit from 3rd party packages. Specifically, mypy throws a "Need type annotation for <field_name>" error on model fields.

Here’s the scenario:

• I created a new project using django-cookiecutter.
• I added mypy v1.11.1, django-stubs v5.0.4, and tested with Django 4.2.11 and 5.0.8.
• I have the following model classes:

class FooBase(models.Model):
    name = models.CharField(max_length=255)

    class Meta:
        abstract = True

class Bar(FooBase):
    updated_at = models.DateTimeField(auto_now=True)

• When both classes are defined in local_app/models.py, there are no errors.
• However, if I move the FooBase class to a 3rd party package’s models.py (e.g., site-packages/django_extensions/models.py since that came with the cookiecutter install), I get a mypy error on the updated_at field of Bar.

This issue only started occurring with django-stubs v5.0.3 or v5.0.4 and mypy v1.11.0 or v1.11.1. It was working correctly with the previous versions (django-stubs v5.0.2 and mypy v1.10.1).

I am aware of issue #2011, which has been closed. However, the difference here is that the code was working fine with the prior django-stubs and mypy versions, but the error occurs after updating to the latest versions.

How is that should be

Type checking should pass without errors when using models that inherit from 3rd party packages, just as it did with previous versions of django-stubs and mypy.

System information

• OS: yes
• python version: 3.11.9
• django version: 5.0.8 & 4.2.11
• mypy version: 1.11.1
• django-stubs version: 5.0.4
• django-stubs-ext version: 5.0.4

mypy Settings

[tool.mypy]
python_version = "3.11"
check_untyped_defs = true
ignore_missing_imports = true
warn_unused_ignores = true
warn_redundant_casts = true
warn_unused_configs = true
plugins = [
    "mypy_django_plugin.main",
]

[Dresdn]

One other fun tidbit of information: not all fields throw an error.

models.FileField(), models.ImageField(), and models.JSONField() don't throw a type error. As far as I can tell, all the others do (IntegerField(), TextField(), etc.)

[YPCrumble]

I believe I'm getting the same issue - it asks for var-annotated on nearly every field in a model that inherits from django extensions' TimeStampedModel, for instance. I believe it was introduced in django-stubs 5.0.3.

[ivan-klass]

I get similar issue with related managers - many of them are not resolved with update to 5.0.4, but a couple of them could be fixed if a model inherited from TimeStampedModel using workaround described here.

#1354 seems relevant.

[Alexerson]

It tried to do a bisect and it seems the issue was maybe introduced in ac36393.

[elnygren]

Getting this with:

mypy==1.13.0
django-stubs==5.1.1
django-extensions==3.2.3

[realsuayip]

Here is a monkeypatch workaround:

import mypy_django_plugin.lib.helpers
from mypy_django_plugin.lib.helpers import is_model_type as patch

allowlist = {
    "dotted.path.to.your.ModelClass",
}


def is_model_type(info):
    if info.fullname in allowlist:
        return True
    return patch(info)


mypy_django_plugin.lib.helpers.is_model_type = is_model_type

It seems that for models inherited from 3rd party apps, info.metaclass_type is None for some reason rather than being model metaclass.

[strokirk]

Another way to resolve this bug when django-stubs errors on django-extensions is to generate stubs with stubgen.

stubgen -m django_extensions.db.models -o stubs
touch django_extensions/__init__.py
touch django_extensions/db/__init__.py

# edit mypy.ini and add mypy_path = stubs
# edit django_extensions/db/models.py and fix any typing issues