ManyToManyField is typed as RelatedManager[<model>] | None rather than just RelatedManager[<model>]

[PureTryOut]

What's wrong

I have the following model:

class Customer(User):
    addresses = models.ManyToManyField(
        Address,
        related_name="customers",
        null=True,
        blank=True,
    )

addresses here is typed as RelatedManager[<model>] | None. meaning any queryset call on it will make mypy complain about the attribute not existing. For example:

project/views/address.py:68: error: Item "None" of "RelatedManager[Address] | None" has no attribute "add"  [union-attr]
project/views/address.py:93: error: Item "None" of "RelatedManager[Address] | None" has no attribute "get"  [union-attr]
project/views/address.py:97: error: Item "None" of "RelatedManager[Address] | None" has no attribute "remove"  [union-attr]

However, it never is None, and I'm not sure how it could be either. If there are no addresses for a customer than customer.addresses.exists() would just return false rather than customer.addresses being None.

How is that should be

It should be typed as just RelatedManager[<model>].

System information

• OS: Linux
• python version: 3.11
• django version: 4.2
• mypy version: 1.4.1
• django-stubs version: 4.2.3
• django-stubs-ext version: not installed

[sobolevn]

Does null=True or blank=True affect | None part?

[andersk]

The ManyToManyField documentation says

null has no effect since there is no way to require a relationship at the database level.

and in fact the system check framework raises the fields.W340 warning for this. django-stubs should ignore null here too, but meanwhile you can just remove it.