Improve typing for unresolved managers

[ljodal]

This changes the logic when encountering an unresolvable manager class. Instead of adding it as a Manager we create a subclass of Manager that has fallback_to_any=True set. Similarly a QuerySet class is created that also has fallbacks to Any. This allows calling custom methods on the manager and querysets without getting type errors.

[flaeppe]

Could we also add a test case having two different unresolvable managers, in the same module, that'll also reveal their model attribute type?

[ljodal]

@flaeppe isn't that what this test is checking?

django-stubs/tests/typecheck/managers/test_managers.yml

Lines 446 to 543 in 2cca99a

	- case: test_emits_error_for_unresolved_managers
	main: |
	from myapp import models
	installed_apps:
	- myapp
	files:
	- path: myapp/__init__.py
	- path: myapp/models.py
	content: |
	from django.db import models
	def LocalManager() -> models.Manager:
	"""
	Returns a manager instance of an inlined manager type that can't
	be resolved.
	"""
	class InnerManager(models.Manager):
	...
	return InnerManager()
	class User(models.Model):
	name = models.TextField()
	class Booking(models.Model):
	renter = models.ForeignKey(User, on_delete=models.PROTECT)
	owner = models.ForeignKey(User, on_delete=models.PROTECT, related_name='bookingowner_set')
	objects = LocalManager()
	class TwoUnresolvable(models.Model):
	objects = LocalManager()
	second_objects = LocalManager()
	class AbstractUnresolvable(models.Model):
	objects = LocalManager()
	class Meta:
	abstract = True
	class InvisibleUnresolvable(AbstractUnresolvable):
	text = models.TextField()
	def process_booking(user: User):
	reveal_type(User.objects)
	reveal_type(User._default_manager)
	reveal_type(Booking.objects)
	reveal_type(Booking._default_manager)
	reveal_type(TwoUnresolvable.objects)
	reveal_type(TwoUnresolvable.second_objects)
	reveal_type(TwoUnresolvable._default_manager)
	reveal_type(InvisibleUnresolvable.objects)
	reveal_type(InvisibleUnresolvable._default_manager)
	reveal_type(user.bookingowner_set)
	reveal_type(user.booking_set)
	# Check QuerySet methods on UnknownManager
	reveal_type(Booking.objects.all)
	reveal_type(Booking.objects.custom)
	reveal_type(Booking.objects.all().filter)
	reveal_type(Booking.objects.all().custom)
	# Check QuerySet methods on UnknownRelatedManager
	reveal_type(user.booking_set.all)
	reveal_type(user.booking_set.custom)
	reveal_type(user.booking_set.all().filter)
	reveal_type(user.booking_set.all().custom)
	out: |
	myapp/models:13: error: Couldn't resolve related manager for relation 'booking' (from myapp.models.Booking.myapp.Booking.renter).
	myapp/models:13: error: Couldn't resolve related manager for relation 'bookingowner_set' (from myapp.models.Booking.myapp.Booking.owner).
	myapp/models:20: error: Could not resolve manager type for "myapp.models.Booking.objects"
	myapp/models:23: error: Could not resolve manager type for "myapp.models.TwoUnresolvable.objects"
	myapp/models:24: error: Could not resolve manager type for "myapp.models.TwoUnresolvable.second_objects"
	myapp/models:27: error: Could not resolve manager type for "myapp.models.AbstractUnresolvable.objects"
	myapp/models:32: error: Could not resolve manager type for "myapp.models.InvisibleUnresolvable.objects"
	myapp/models:36: note: Revealed type is "django.db.models.manager.Manager[myapp.models.User]"
	myapp/models:37: note: Revealed type is "django.db.models.manager.Manager[myapp.models.User]"
	myapp/models:39: note: Revealed type is "myapp.models.UnknownManager[myapp.models.Booking]"
	myapp/models:40: note: Revealed type is "django.db.models.manager.BaseManager[myapp.models.Booking]"
	myapp/models:42: note: Revealed type is "myapp.models.UnknownManager[myapp.models.TwoUnresolvable]"
	myapp/models:43: note: Revealed type is "myapp.models.UnknownManager[myapp.models.TwoUnresolvable]"
	myapp/models:44: note: Revealed type is "django.db.models.manager.BaseManager[myapp.models.TwoUnresolvable]"
	myapp/models:46: note: Revealed type is "myapp.models.UnknownManager[myapp.models.InvisibleUnresolvable]"
	myapp/models:47: note: Revealed type is "django.db.models.manager.BaseManager[myapp.models.InvisibleUnresolvable]"
	myapp/models:49: note: Revealed type is "myapp.models.UnknownRelatedManager[myapp.models.Booking]"
	myapp/models:50: note: Revealed type is "myapp.models.UnknownRelatedManager[myapp.models.Booking]"
	myapp/models:53: note: Revealed type is "def () -> myapp.models.UnknownQuerySet[myapp.models.Booking]"
	myapp/models:54: note: Revealed type is "Any"
	myapp/models:55: note: Revealed type is "def (*args: Any, **kwargs: Any) -> myapp.models.UnknownQuerySet[myapp.models.Booking]"
	myapp/models:56: note: Revealed type is "Any"
	myapp/models:59: note: Revealed type is "def () -> myapp.models.UnknownQuerySet[myapp.models.Booking]"
	myapp/models:60: note: Revealed type is "Any"
	myapp/models:61: note: Revealed type is "def (*args: Any, **kwargs: Any) -> myapp.models.UnknownQuerySet[myapp.models.Booking]"
	myapp/models:62: note: Revealed type is "Any"

[ljodal]

I've found a bug with this implementation, so hold off on merging until I have that under control :)

Edit: Fixed now ✅

[ljodal]

@sobolevn Any plans to merge this and the few other PRs that should be ready? We're currently running with this branch at work and it's been working fine (both 1.11 and 1.12 is unusable for us due to phantom type errors :().

I also have a few other things on my list to fix (like #960), but I'll get too many merge conflicts so I'm holding off for now

[sobolevn]

Sorry for the delay, I was on vacation. Can you please resolve merge conflicts?

[ljodal]

Sorry for the delay, I was on vacation. Can you please resolve merge conflicts?

No worries, I assumed as much. The conflicts should be resolved now :)

[sobolevn]

Thank you!