DJ008 (__str__ method) fails when inheriting from multiple models, and str only defined in other module

[zyzzyxdonta]

This is related to #9242.

When a Django model inherits from an abstract model in the same module and a model in a different module, the __str__ from the other module is not recognized and trips DJ008.

This is a minimal example that reproduces this behaviour:

ruff-bug-repro.zip

.
├── mypackage
│   ├── core
│   │   ├── __init__.py
│   │   └── models.py
│   ├── __init__.py
│   └── resources
│       ├── __init__.py
│       └── models.py
└── pyproject.toml

Core models:

from django.db import models

class Thing(models.Model):
    label = models.TextField()

    def __str__(self):
        return self.label or str(self.pk)

Resources models:

from django.db import models

from mypackage.core.models import Thing


class Resource(models.Model):
    resource_id = models.AutoField(primary_key=True)

    class Meta:
        abstract = True


class Job(Resource, Thing):
    job_id = models.TextField()

Output from ruff 0.9.1:

mypackage/resources/models.py:13:7: DJ008 Model does not define `__str__` method
   |
13 | class Job(Resource, Thing):
   |       ^^^ DJ008
14 |     job_id = models.TextField()
   |

Found 1 error.

Thanks!

[dhruvmanila]

I wonder if we should ignore this rule when the subclass is coming from a different file to reduce the false positive but that does come with the possibility of increasing the false negative.