[5.0.3 regression] Can’t `filter` a `QuerySet` on an `alias`

[andersk]

from django.db import models

class Blog(models.Model):
    pass

class Entry(models.Model):
    blog = models.ForeignKey(Blog, on_delete=models.CASCADE)

def test() -> None:
    Blog.objects.alias(entries=models.Count("entry")).filter(entries__gt=5)

my_app/models.py:13: error: Cannot resolve keyword 'entries' into field. Choices are: entry, id  [misc]
Found 1 error in 1 file (checked 3 source files)

This was introduced by a28717d (#2277).

[flaeppe]

I don't know if we should call this a regression? Any version prior to 5.0.3 just didn't try to check the filter call.

At least there's no plugin code that tries to do anything with alias

[andersk]

From a user perspective, this was allowed in 5.0.2 and incorrectly disallowed in 5.0.3. Whatever you’d like to call it, we can’t upgrade to django-stubs ≥ 5.0.3 in Zulip until it’s addressed.

[sobolevn]

Really interesting: there are no handlers for alias in

django-stubs/mypy_django_plugin/main.py

Lines 168 to 181 in b76f9f4

	@cached_property
	def manager_and_queryset_method_hooks(self) -> Dict[str, Callable[[MethodContext], MypyType]]:
	typecheck_filtering_method = partial(orm_lookups.typecheck_queryset_filter, django_context=self.django_context)
	return {
	"values": partial(querysets.extract_proper_type_queryset_values, django_context=self.django_context),
	"values_list": partial(
	querysets.extract_proper_type_queryset_values_list, django_context=self.django_context
	),
	"annotate": partial(querysets.extract_proper_type_queryset_annotate, django_context=self.django_context),
	"create": partial(init_create.redefine_and_typecheck_model_create, django_context=self.django_context),
	"filter": typecheck_filtering_method,
	"get": typecheck_filtering_method,
	"exclude": typecheck_filtering_method,
	}

I will start digging into this!

[sobolevn]

The problem happens because we use entries__gt=5 in filter, which should be allowed. We need to add alias() support and infer field names from there.