ManyToManyField not typed properly when using import alias for related model

[tkoft]

Bug report

What's wrong

Looks like the transformer for ManyToManyField doesn't handle the case for when the related model passed in is aliased. The to model is still typed properly, since it's inferred and returned as the FunctionContext default_return_type, but any generated through model is never typed.

Example:

from django.contrib.auth import models as auth_models
from django.db import models

class MyModel(models.Model):
    allowed_groups = models.ManyToManyField(auth_models.Group)

I believe get_model_from_expression() gets passed a MemberExpr as such:

MemberExpr:11(
  NameExpr(auth_models [django.contrib.auth.models])
  Group [django.contrib.auth.models.Group])

But this case is only handled explicitly for the django.contrib.auth.models.User model. In other cases, it returns None, and the transform for the whole field just returns the default value.

How is that should be

Since normal RelatedFields resolve their related models fine with aliased imports, it seems the manytomany transformer should be able to use the same logic (a la django_context.get_field_related_model_cls(current_field)) for resolving both its to and through models. Though I'm sure there's some complexities around how Django models m2m relations that would require some changes from how get_field_related_model_cls works.

System information

• OS:
• python version: 3.8
• django version: 4.2.9
• mypy version: 1.10
• django-stubs version: 5.0
• django-stubs-ext version:

[tkoft]

Actually, I think the easiest fix is to change this condition to check for RefExpr instead of NameExpr:

django-stubs/mypy_django_plugin/transformers/manytomany.py

Line 132 in 4a5b065

if isinstance(expr, NameExpr) and isinstance(expr.node, TypeInfo):

[flaeppe]

Thanks for the clear report and a fix, I've opened #2153 with your suggestion