Inheriting from model_utils SoftDeletableModel causes issues

[JannKleen]

Bug report

What's wrong

I'm using https://github.com/jazzband/django-model-utils/blob/master/model_utils/models.py#L133-L158 (I know this isn't a great implementation for soft deletion, but I needed something quick and simple) and have the following models set up:

from model_utils.models import SoftDeletableModel


class BaseModel(SoftDeletableModel):
    class Meta:
        abstract = True

class MyModelA(BaseModel):
    sub_items = models.ManyToManyField(
        "self", related_name="parents", symmetrical=False, blank=True
    )

class MyModelB(BaseModel):
    model_a = models.ManyToManyField(MyModelA, related_name="model_b")
    deleted_model_a = models.ManyToManyField(MyModelA, related_name="model_b_deleted")

This works fine if I don't inherit from SoftDeletableModel but if I do I get:

error: Need type annotation for "sub_items"  [var-annotated]
error: Need type annotation for "model_a"  [var-annotated]
error: Need type annotation for "deleted_model_a"  [var-annotated]

System information

• OS: Linux (python:3.11.7-slim-bullseye)
• python version: 3.11.7
• django version: django==4.2.7
• mypy version: mypy==1.7.0
• django-stubs version: django-stubs[compatible-mypy]==4.2.7
• django-stubs-ext version: django-stubs-ext==4.2.7

[JannKleen]

What works is manually annotating those fields with field : models.ManyToManyField = ....

[flaeppe]

I'm not completely sure; but since SoftDeletableModel seem to lack type hints it might be that mypy can't resolve that class/type properly.

With the above said it looks like this is rather an issue (at least initially) for django-model-utils than for django-stubs.

I'm happy to reopen if it there's anything else that I might have missed and would need to be fixed.

[JannKleen]

@flaeppe Thanks for the reply! I get that this is more related to django-model-utils, but since you're probably more familiar with python (and Django) typing, could you maybe point me at what could cause the issue? It doesn't look like they're doing anything crazy, is it the Mixin that could be causing this?

[intgr]

I don't understand either, why this would happen. While django-model-utils is missing many specific type hints, it actually includes a py.typed marker. So mypy should be fully aware that SoftDeletableModel inherits from models.Model.

If you're looking for a quick work-around hack, this might help:

from typing import TYPE_CHECKING

class BaseModel(models.Model if TYPE_CHECKING else SoftDeletableModel):