RelatedField.related_query_name should default to _meta.default_related_name if defined.

[Daniel Bate]

If I attach a default_related_name for my model using the name in a model lookup fails.

For example, if I have the following models:

from django.db import models

class Foo(models.Model):
    a = models.IntegerField(default=0)


class Bar(models.Model):
    foo = models.ForeignKey(Foo, related_name='bars')


class Boo(models.Model):
    foo = models.ForeignKey(Foo)

    class Meta:
        default_related_name = 'boos'

And the following tests:

from django.test import TestCase

from .models import Foo, Bar, Boo


class Test(TestCase):
    def setUp(self):
        self.foo = Foo.objects.create()

    def test_related_name_on_field___all_is_fine(self):
        instance = Bar.objects.create(foo=self.foo)

        # get related set
        self.assertEqual(instance, self.foo.bars.first())

        # filter foos through lookup
        self.assertEqual(self.foo, Foo.objects.get(bars=instance))

    def test_related_name_is_default___lookup_fails(self):
        instance = Boo.objects.create(foo=self.foo)

        # get related set
        self.assertEqual(instance, self.foo.boos.first())

        # filter foos through lookup
        self.assertEqual(self.foo, Foo.objects.get(boos=instance))

I get the following error:

django.core.exceptions.FieldError: Cannot resolve keyword 'boos' into field. Choices are: a, bars, boo, id

This shows I can use boos as a property for Foo objects but when i try to use it in a lookup it is expecting boo rather than boos

[Simon Charette]

This was also brought up on ​django-users a couple of months ago.

[Yi-Shan, Chen]

I'll work on this in the next few days.

[Yi-Shan, Chen]

PR ​https://github.com/django/django/pull/6187

[Tim Graham]

The pull request is backwards-incompatible. It would be nice to have a deprecation path if possible.

[Tim Graham <timograham@…>]

In b84f5ab4:

Fixed #26230 -- Made default_related_name affect related_query_name.

[Tim Graham <timograham@…>]

In bfe0d54:

Refs #26230 -- Removed support for model name query lookups when using Meta.default_related_name.

Per deprecation timeline.