error: Couldn't resolve related manager for relation on python3.11 and django3.2

[marsha97]

Bug report

What's wrong

I got Couldn't resolve related manager for relation error when using python3.11 and django3.2.
So the model looks like

# dummy/apps/foos/models.py

class Foo(models.Model):
    ....

# dummy/apps/bars/models.py

class BarQueryset(models.Queryset):
    ...

class Bar(models.Model):
    ...
   foo = models.Foreignkey('foos.Foo', related_name='bars')
   objects = models.Manager.from_queryset(BarQueryset)()

I will get the following error:
dummy/apps/foos/models.py:###: error: Couldn't resolve related manager for relation 'bars' (from dummy.apps.bars.models.Bar.bars.Bar.foo). [django-manager-missing]

It seems only happen when the reverse foreign key has a custom objects like Bar above...
And may be related to #1285

I have to use # type: ignore for now to silent this...

How is that should be

Should have no problem. I tried to downgrade python back to python3.9, mypy==0.812, and django-stubs==1.8.0 and it has no issue.

System information

• OS: ubuntu 20
• python version: 3.11
• django version: 3.2.16
• mypy version: 0.991
• django-stubs version: 1.14.0
• django-stubs-ext version: 0.7.0

[ljodal]

I tried to downgrade python back to python3.9, mypy==0.812, and django-stubs==1.8.0 and it has no issue.

Are you sure you're getting typing on that setup? I introduced this error message a while back, but it was only to surface issues that were previously silently ignored.

Basically, this error means that the plugin was not able to statically figure out what class the manager would be. Typically that means you're doing something in your code that's not statically checkable (or not supported by the plugin). Are you able to create a minimal example that reproduces the issue?

[marsha97]

I tried to downgrade python back to python3.9, mypy==0.812, and django-stubs==1.8.0 and it has no issue.

Are you sure you're getting typing on that setup? I introduced this error message a while back, but it was only to surface issues that were previously silently ignored.

Basically, this error means that the plugin was not able to statically figure out what class the manager would be. Typically that means you're doing something in your code that's not statically checkable (or not supported by the plugin). Are you able to create a minimal example that reproduces the issue?

ooh, right. I noticed something else, this will happen if the reverse FK class inherit from this 3rd party class https://github.com/jazzband/django-model-utils/blob/cced1c7aeaf97fa6ee5c7e44c8ea827ed10b2da5/model_utils/models.py#L19
Still has no idea how to resolve this

so the simple code will looks like:

# apps/foos/models.py

from django.db import models


class Foo(models.Model):
    field1 = models.PositiveSmallIntegerField()

# apps/bars/models.py

from django.db import models
from model_utils.models import TimeStampedModel


class BarQueryset(models.QuerySet):
    def get_active_qs(self) -> models.QuerySet:
        return self.filter(is_active=True)


class Bar(TimeStampedModel):
    foo = models.ForeignKey("foos.Foo", related_name="bars", on_delete=models.CASCADE)
    is_active = models.BooleanField(default=False)
    objects = models.Manager.from_queryset(BarQueryset)()

this will results in:
dummy/apps/foos/models.py:4: error: Couldn't resolve related manager for relation 'bars' (from dummy.apps.bars.models.Bar.bars.Bar.foo). [django-manager-missing]

removing the custom objects attribute will produce the same error.

but, it will be fine if I changed the Bar model into something like this:

from django.db import models


class BarQueryset(models.QuerySet):
    def get_active_qs(self) -> models.QuerySet:
        return self.filter(is_active=True)


class BaseBar(models.Model):
    name = models.CharField(max_length=255)


class Bar(BaseBar):
    foo = models.ForeignKey("foos.Foo", related_name="bars", on_delete=models.CASCADE)
    is_active = models.BooleanField(default=False)
    objects = models.Manager.from_queryset(BarQueryset)()

[ljodal]

Ah, alright. I guess the error message could be improved here, but basically it appears that TimeStampedModel has its managers dynamically added, which is hard/impossible to statically type check.

[intgr]

I didn't look into this in detail, but maybe it helps to add manual type hints to the Model class for these manager attributes?

[baileywickham]

I was able to fix this issue by annotating the related name. In this case it would be

class Foo:
    field1 = models.PositiveSmallIntegerField()
    bars: "QuerySet[Bar]"
    # or if related_name isn't set:
    bar_set: "QuerySet[Bar]"

[ibadarrohman]

I was able to fix this issue by annotating the related name. In this case it would be

class Foo:
    field1 = models.PositiveSmallIntegerField()
    bars: "QuerySet[Bar]"
    # or if related_name isn't set:
    bar_set: "QuerySet[Bar]"

Annotating with RelatedManager[Bar] from django.db.models.manager.RelatedManager also works.

[flaeppe]

I deem that either any of the suggested approaches with explicit annotation is a resolution or if there's 3rd party code involved(ref: #1354 (comment)) this is a duplicate of #1023.

Feel free to correct me if I'm wrong.

[browser-bug]

I was able to fix this issue by annotating the related name. In this case it would be

class Foo:
    field1 = models.PositiveSmallIntegerField()
    bars: "QuerySet[Bar]"
    # or if related_name isn't set:
    bar_set: "QuerySet[Bar]"

Annotating with RelatedManager[Bar] from django.db.models.manager.RelatedManager also works.

This would throw Module "django.db.models.manager" has no attribute "RelatedManager" , correct me if I'm wrong.