"RelatedModel" has no attribute "RelatedObjectDoesNotExist" [attr-defined]

[eternal-sorrow]

Bug report

What's wrong

Mypy prints Module "django.db.models" has no attribute "ObjectDoesNotExist" [attr-defined] on the from django.db.models import ObjectDoesNotExist line, which is obviously wrong.

Also, if I alternatively use MyModel.field.RelatedObjectDoesNotExist, I get the "RelatedModel" has no attribute "RelatedObjectDoesNotExist" [attr-defined] message.

field here is a reverse relation from RelatedModel to MyModel one-to-one field.

How is that should be

No error messages.

System information

• OS:
• python version: 3.10.6
• django version: 3.2.18
• mypy version: 1.0.1
• django-stubs version: 1.15.0
• django-stubs-ext version: 0.7.0

[intgr]

Hi. This was caused by #1309, which removes re-exports that are not part of Django's intentional public API.

According to Django documentation https://docs.djangoproject.com/en/4.1/ref/exceptions/ the exception ObjectDoesNotExist should be imported from django.core.exceptions, not from django.db.models.

[eternal-sorrow]

Alright, that's valid. The second prat of the bug report still applies.

[intgr]

Ah sorry I missed the second part. You're right, that's a bug. Looks like it could be complicated.

[RyanWalker277]

Hey! @eternal-sorrow can you share the code snippet in which you encountered the bug? On a quick lookup in related_descriptors.pyi

django-stubs/django-stubs/db/models/fields/related_descriptors.pyi

Lines 19 to 34 in 0aa7bf1

	class ForwardManyToOneDescriptor:
	field: ForeignKey
	def __init__(self, field_with_rel: ForeignKey) -> None: ...
	@property
	def RelatedObjectDoesNotExist(self) -> type[ObjectDoesNotExist]: ...
	def is_cached(self, instance: Model) -> bool: ...
	def get_queryset(self, **hints: Any) -> QuerySet: ...
	def get_prefetch_queryset(
	self, instances: list[Model], queryset: QuerySet | None = ...
	) -> tuple[QuerySet, Callable, Callable, bool, str, bool]: ...
	def get_object(self, instance: Model) -> Model: ...
	def __get__(
	self, instance: Model | None, cls: type[Model] | None = ...
	) -> Model | ForwardManyToOneDescriptor | None: ...
	def __set__(self, instance: Model, value: Model | None) -> None: ...
	def __reduce__(self) -> tuple[Callable, tuple[type[Model], str]]: ...

django-stubs/django-stubs/db/models/fields/related_descriptors.pyi

Lines 40 to 52 in 0aa7bf1

	class ReverseOneToOneDescriptor:
	related: OneToOneRel
	def __init__(self, related: OneToOneRel) -> None: ...
	@property
	def RelatedObjectDoesNotExist(self) -> type[ObjectDoesNotExist]: ...
	def is_cached(self, instance: Model) -> bool: ...
	def get_queryset(self, **hints: Any) -> QuerySet: ...
	def get_prefetch_queryset(
	self, instances: list[Model], queryset: QuerySet | None = ...
	) -> tuple[QuerySet, Callable, Callable, bool, str, bool]: ...
	def __get__(self, instance: Model | None, cls: type[Model] | None = ...) -> Model | ReverseOneToOneDescriptor: ...
	def __set__(self, instance: Model, value: Model | None) -> None: ...
	def __reduce__(self) -> tuple[Callable, tuple[type[Model], str]]: ...

One thing that I think that might be causing the issue can be the fact that the RelatedObjectDoesNotExist attribute is defined as a property in the ForwardManyToOneDescriptor and ReverseOneToOneDescriptor classes, but it is not defined in the ManyToManyDescriptor class. This could result in the error when using MyModel.field.RelatedObjectDoesNotExist if field is a ManyToManyField. I may be wrong and something else might be causing the issue, just wanted to have a discussion on the potential causes before working on this one.

[eternal-sorrow]

field here is a reverse relation for a one-to-one field. I looks something like this:

class A(models.Model):
    ...

class B(models.Model):
    a = models.OneToOneField(A, related_name='b')

a = A.objects.first()
try:
    b = a.b
except A.b.RelatedObjectDoesNotExist:  # mypy complains here '"B" has no attribute "RelatedObjectDoesNotExist"'
    pass

[flaeppe]

Closed via #1733