Cannot resolve manager type when using django-polymorphic

[AntoineRondelet]

Bug report

Hi, I'm not sure if this is a genuine bug or if I am just doing something wrong.
I recently used django-polymorphic to add a new feature in my project and mypy is now breaking. I have plenty of errors:

error: Could not resolve manager type for "<MyModel>.objects"

and

error: Couldn't resolve related manager for relation '<related_name>'

After checking the django polymorphic docs: https://django-polymorphic.readthedocs.io/en/stable/managers.html#manager-inheritance I can see that the manager is inherited. Could that be the source of mypy's troubles here? I feel it could be, but I'd be happy to get opinions.

Is that a known issue with django-polymorphic that I simply am not aware of? If so, is there a (concise) way around it? If not, I'll probably fallback to the "multiple FK in a model" approach to keep mypy running...

Happy to hear if I'm missing something obvious!
Thanks in advance! :)

System information

• OS: macOS Monterey 12.6
• python version: 3.10.6
• django version: 4.1
• mypy version: 0.971
• django-stubs version: 1.12.0
• django-stubs-ext version: 0.5.0

[AntoineRondelet]

To add to this, here's basically what I'm doing:

class Thing(PolymorphicModel):

    id = models.UUIDField(
        default=uuid.uuid4, unique=True, primary_key=True, editable=False
    )

    created = models.DateTimeField(auto_now_add=True)

    class Meta:
        ordering = ["-created"]

I then use this in another module

class SpecificThing(Thing):

    text = models.CharField(max_length=10)

and I define explicit through models for relationships

class SpecificThingRelationship(models.Model):

    source = models.ForeignKey(User, on_delete=models.CASCADE, related_name="things")
    target = models.ForeignKey(SpecificThing, on_delete=models.CASCADE, related_name="users")

[AntoineRondelet]

May be related to #1023

[sterliakov]

CC: https://stackoverflow.com/questions/73866986/cannot-resolve-manager-type-when-using-django-polymorphic-with-mypy-django-stubs

[jose-reveni]

Is there any known workaround for this? I've tried disabling the django-manager-missing error code in mypy but that doesn't work (python/mypy#12987), so I'm stuck using v0.950 :(

Also, I think this issue might be a duplicate of #1023