django/tests/migrations/test_state.py

from django.apps.registry import Apps
from django.contrib.contenttypes.fields import GenericForeignKey
from django.db import models
from django.db.migrations.exceptions import InvalidBasesError
from django.db.migrations.operations import (
    AddField, AlterField, DeleteModel, RemoveField,
)
from django.db.migrations.state import (
    ModelState, ProjectState, get_related_models_recursive,
)
from django.test import SimpleTestCase, override_settings
from django.test.utils import isolate_apps

from .models import (
    FoodManager, FoodQuerySet, ModelWithCustomBase, NoMigrationFoodManager,
    UnicodeModel,
)


class StateTests(SimpleTestCase):
    """
    Tests state construction, rendering and modification by operations.
    """

    def test_create(self):
        """
        Tests making a ProjectState from an Apps
        """

        new_apps = Apps(["migrations"])

        class Author(models.Model):
            name = models.CharField(max_length=255)
            bio = models.TextField()
            age = models.IntegerField(blank=True, null=True)

            class Meta:
                app_label = "migrations"
                apps = new_apps
                unique_together = ["name", "bio"]
                index_together = ["bio", "age"]

        class AuthorProxy(Author):
            class Meta:
                app_label = "migrations"
                apps = new_apps
                proxy = True
                ordering = ["name"]

        class SubAuthor(Author):
            width = models.FloatField(null=True)

            class Meta:
                app_label = "migrations"
                apps = new_apps

        class Book(models.Model):
            title = models.CharField(max_length=1000)
            author = models.ForeignKey(Author, models.CASCADE)
            contributors = models.ManyToManyField(Author)

            class Meta:
                app_label = "migrations"
                apps = new_apps
                verbose_name = "tome"
                db_table = "test_tome"
                indexes = [models.Index(fields=['title'])]

        class Food(models.Model):

            food_mgr = FoodManager('a', 'b')
            food_qs = FoodQuerySet.as_manager()
            food_no_mgr = NoMigrationFoodManager('x', 'y')

            class Meta:
                app_label = "migrations"
                apps = new_apps

        class FoodNoManagers(models.Model):

            class Meta:
                app_label = "migrations"
                apps = new_apps

        class FoodNoDefaultManager(models.Model):

            food_no_mgr = NoMigrationFoodManager('x', 'y')
            food_mgr = FoodManager('a', 'b')
            food_qs = FoodQuerySet.as_manager()

            class Meta:
                app_label = "migrations"
                apps = new_apps

        mgr1 = FoodManager('a', 'b')
        mgr2 = FoodManager('x', 'y', c=3, d=4)

        class FoodOrderedManagers(models.Model):
            # The managers on this model should be ordered by their creation
            # counter and not by the order in model body

            food_no_mgr = NoMigrationFoodManager('x', 'y')
            food_mgr2 = mgr2
            food_mgr1 = mgr1

            class Meta:
                app_label = "migrations"
                apps = new_apps

        project_state = ProjectState.from_apps(new_apps)
        author_state = project_state.models['migrations', 'author']
        author_proxy_state = project_state.models['migrations', 'authorproxy']
        sub_author_state = project_state.models['migrations', 'subauthor']
        book_state = project_state.models['migrations', 'book']
        food_state = project_state.models['migrations', 'food']
        food_no_managers_state = project_state.models['migrations', 'foodnomanagers']
        food_no_default_manager_state = project_state.models['migrations', 'foodnodefaultmanager']
        food_order_manager_state = project_state.models['migrations', 'foodorderedmanagers']
        book_index = models.Index(fields=['title'])
        book_index.set_name_with_model(Book)

        self.assertEqual(author_state.app_label, "migrations")
        self.assertEqual(author_state.name, "Author")
        self.assertEqual(list(author_state.fields), ["id", "name", "bio", "age"])
        self.assertEqual(author_state.fields['name'].max_length, 255)
        self.assertIs(author_state.fields['bio'].null, False)
        self.assertIs(author_state.fields['age'].null, True)
        self.assertEqual(
            author_state.options,
            {
                "unique_together": {("name", "bio")},
                "index_together": {("bio", "age")},
                "indexes": [],
                "constraints": [],
            }
        )
        self.assertEqual(author_state.bases, (models.Model,))

        self.assertEqual(book_state.app_label, "migrations")
        self.assertEqual(book_state.name, "Book")
        self.assertEqual(list(book_state.fields), ["id", "title", "author", "contributors"])
        self.assertEqual(book_state.fields['title'].max_length, 1000)
        self.assertIs(book_state.fields['author'].null, False)
        self.assertEqual(book_state.fields['contributors'].__class__.__name__, 'ManyToManyField')
        self.assertEqual(
            book_state.options,
            {"verbose_name": "tome", "db_table": "test_tome", "indexes": [book_index], "constraints": []},
        )
        self.assertEqual(book_state.bases, (models.Model,))

        self.assertEqual(author_proxy_state.app_label, "migrations")
        self.assertEqual(author_proxy_state.name, "AuthorProxy")
        self.assertEqual(author_proxy_state.fields, {})
        self.assertEqual(
            author_proxy_state.options,
            {"proxy": True, "ordering": ["name"], "indexes": [], "constraints": []},
        )
        self.assertEqual(author_proxy_state.bases, ("migrations.author",))

        self.assertEqual(sub_author_state.app_label, "migrations")
        self.assertEqual(sub_author_state.name, "SubAuthor")
        self.assertEqual(len(sub_author_state.fields), 2)
        self.assertEqual(sub_author_state.bases, ("migrations.author",))

        # The default manager is used in migrations
        self.assertEqual([name for name, mgr in food_state.managers], ['food_mgr'])
        self.assertTrue(all(isinstance(name, str) for name, mgr in food_state.managers))
        self.assertEqual(food_state.managers[0][1].args, ('a', 'b', 1, 2))

        # No explicit managers defined. Migrations will fall back to the default
        self.assertEqual(food_no_managers_state.managers, [])

        # food_mgr is used in migration but isn't the default mgr, hence add the
        # default
        self.assertEqual([name for name, mgr in food_no_default_manager_state.managers],
                         ['food_no_mgr', 'food_mgr'])
        self.assertTrue(all(isinstance(name, str) for name, mgr in food_no_default_manager_state.managers))
        self.assertEqual(food_no_default_manager_state.managers[0][1].__class__, models.Manager)
        self.assertIsInstance(food_no_default_manager_state.managers[1][1], FoodManager)

        self.assertEqual([name for name, mgr in food_order_manager_state.managers],
                         ['food_mgr1', 'food_mgr2'])
        self.assertTrue(all(isinstance(name, str) for name, mgr in food_order_manager_state.managers))
        self.assertEqual([mgr.args for name, mgr in food_order_manager_state.managers],
                         [('a', 'b', 1, 2), ('x', 'y', 3, 4)])

    def test_custom_default_manager_added_to_the_model_state(self):
        """
        When the default manager of the model is a custom manager,
        it needs to be added to the model state.
        """
        new_apps = Apps(['migrations'])
        custom_manager = models.Manager()

        class Author(models.Model):
            objects = models.TextField()
            authors = custom_manager

            class Meta:
                app_label = 'migrations'
                apps = new_apps

        project_state = ProjectState.from_apps(new_apps)
        author_state = project_state.models['migrations', 'author']
        self.assertEqual(author_state.managers, [('authors', custom_manager)])

    def test_custom_default_manager_named_objects_with_false_migration_flag(self):
        """
        When a manager is added with a name of 'objects' but it does not
        have `use_in_migrations = True`, no migration should be added to the
        model state (#26643).
        """
        new_apps = Apps(['migrations'])

        class Author(models.Model):
            objects = models.Manager()

            class Meta:
                app_label = 'migrations'
                apps = new_apps

        project_state = ProjectState.from_apps(new_apps)
        author_state = project_state.models['migrations', 'author']
        self.assertEqual(author_state.managers, [])

    def test_no_duplicate_managers(self):
        """
        When a manager is added with `use_in_migrations = True` and a parent
        model had a manager with the same name and `use_in_migrations = True`,
        the parent's manager shouldn't appear in the model state (#26881).
        """
        new_apps = Apps(['migrations'])

        class PersonManager(models.Manager):
            use_in_migrations = True

        class Person(models.Model):
            objects = PersonManager()

            class Meta:
                abstract = True

        class BossManager(PersonManager):
            use_in_migrations = True

        class Boss(Person):
            objects = BossManager()

            class Meta:
                app_label = 'migrations'
                apps = new_apps

        project_state = ProjectState.from_apps(new_apps)
        boss_state = project_state.models['migrations', 'boss']
        self.assertEqual(boss_state.managers, [('objects', Boss.objects)])

    def test_custom_default_manager(self):
        new_apps = Apps(['migrations'])

        class Author(models.Model):
            manager1 = models.Manager()
            manager2 = models.Manager()

            class Meta:
                app_label = 'migrations'
                apps = new_apps
                default_manager_name = 'manager2'

        project_state = ProjectState.from_apps(new_apps)
        author_state = project_state.models['migrations', 'author']
        self.assertEqual(author_state.options['default_manager_name'], 'manager2')
        self.assertEqual(author_state.managers, [('manager2', Author.manager1)])

    def test_custom_base_manager(self):
        new_apps = Apps(['migrations'])

        class Author(models.Model):
            manager1 = models.Manager()
            manager2 = models.Manager()

            class Meta:
                app_label = 'migrations'
                apps = new_apps
                base_manager_name = 'manager2'

        class Author2(models.Model):
            manager1 = models.Manager()
            manager2 = models.Manager()

            class Meta:
                app_label = 'migrations'
                apps = new_apps
                base_manager_name = 'manager1'

        project_state = ProjectState.from_apps(new_apps)

        author_state = project_state.models['migrations', 'author']
        self.assertEqual(author_state.options['base_manager_name'], 'manager2')
        self.assertEqual(author_state.managers, [
            ('manager1', Author.manager1),
            ('manager2', Author.manager2),
        ])

        author2_state = project_state.models['migrations', 'author2']
        self.assertEqual(author2_state.options['base_manager_name'], 'manager1')
        self.assertEqual(author2_state.managers, [
            ('manager1', Author2.manager1),
        ])

    def test_apps_bulk_update(self):
        """
        StateApps.bulk_update() should update apps.ready to False and reset
        the value afterward.
        """
        project_state = ProjectState()
        apps = project_state.apps
        with apps.bulk_update():
            self.assertFalse(apps.ready)
        self.assertTrue(apps.ready)
        with self.assertRaises(ValueError):
            with apps.bulk_update():
                self.assertFalse(apps.ready)
                raise ValueError()
        self.assertTrue(apps.ready)

    def test_render(self):
        """
        Tests rendering a ProjectState into an Apps.
        """
        project_state = ProjectState()
        project_state.add_model(ModelState(
            app_label="migrations",
            name="Tag",
            fields=[
                ("id", models.AutoField(primary_key=True)),
                ("name", models.CharField(max_length=100)),
                ("hidden", models.BooleanField()),
            ],
        ))
        project_state.add_model(ModelState(
            app_label="migrations",
            name="SubTag",
            fields=[
                ('tag_ptr', models.OneToOneField(
                    'migrations.Tag',
                    models.CASCADE,
                    auto_created=True,
                    parent_link=True,
                    primary_key=True,
                    to_field='id',
                    serialize=False,
                )),
                ("awesome", models.BooleanField()),
            ],
            bases=("migrations.Tag",),
        ))

        base_mgr = models.Manager()
        mgr1 = FoodManager('a', 'b')
        mgr2 = FoodManager('x', 'y', c=3, d=4)
        project_state.add_model(ModelState(
            app_label="migrations",
            name="Food",
            fields=[
                ("id", models.AutoField(primary_key=True)),
            ],
            managers=[
                # The ordering we really want is objects, mgr1, mgr2
                ('default', base_mgr),
                ('food_mgr2', mgr2),
                ('food_mgr1', mgr1),
            ]
        ))

        new_apps = project_state.apps
        self.assertEqual(new_apps.get_model("migrations", "Tag")._meta.get_field("name").max_length, 100)
        self.assertIs(new_apps.get_model("migrations", "Tag")._meta.get_field("hidden").null, False)

        self.assertEqual(len(new_apps.get_model("migrations", "SubTag")._meta.local_fields), 2)

        Food = new_apps.get_model("migrations", "Food")
        self.assertEqual([mgr.name for mgr in Food._meta.managers],
                         ['default', 'food_mgr1', 'food_mgr2'])
        self.assertTrue(all(isinstance(mgr.name, str) for mgr in Food._meta.managers))
        self.assertEqual([mgr.__class__ for mgr in Food._meta.managers],
                         [models.Manager, FoodManager, FoodManager])

    def test_render_model_inheritance(self):
        class Book(models.Model):
            title = models.CharField(max_length=1000)

            class Meta:
                app_label = "migrations"
                apps = Apps()

        class Novel(Book):
            class Meta:
                app_label = "migrations"
                apps = Apps()

        # First, test rendering individually
        apps = Apps(["migrations"])

        # We shouldn't be able to render yet
        ms = ModelState.from_model(Novel)
        with self.assertRaises(InvalidBasesError):
            ms.render(apps)

        # Once the parent model is in the app registry, it should be fine
        ModelState.from_model(Book).render(apps)
        ModelState.from_model(Novel).render(apps)

    def test_render_model_with_multiple_inheritance(self):
        class Foo(models.Model):
            class Meta:
                app_label = "migrations"
                apps = Apps()

        class Bar(models.Model):
            class Meta:
                app_label = "migrations"
                apps = Apps()

        class FooBar(Foo, Bar):
            class Meta:
                app_label = "migrations"
                apps = Apps()

        class AbstractSubFooBar(FooBar):
            class Meta:
                abstract = True
                apps = Apps()

        class SubFooBar(AbstractSubFooBar):
            class Meta:
                app_label = "migrations"
                apps = Apps()

        apps = Apps(["migrations"])

        # We shouldn't be able to render yet
        ms = ModelState.from_model(FooBar)
        with self.assertRaises(InvalidBasesError):
            ms.render(apps)

        # Once the parent models are in the app registry, it should be fine
        ModelState.from_model(Foo).render(apps)
        self.assertSequenceEqual(ModelState.from_model(Foo).bases, [models.Model])
        ModelState.from_model(Bar).render(apps)
        self.assertSequenceEqual(ModelState.from_model(Bar).bases, [models.Model])
        ModelState.from_model(FooBar).render(apps)
        self.assertSequenceEqual(ModelState.from_model(FooBar).bases, ['migrations.foo', 'migrations.bar'])
        ModelState.from_model(SubFooBar).render(apps)
        self.assertSequenceEqual(ModelState.from_model(SubFooBar).bases, ['migrations.foobar'])

    def test_render_project_dependencies(self):
        """
        The ProjectState render method correctly renders models
        to account for inter-model base dependencies.
        """
        new_apps = Apps()

        class A(models.Model):
            class Meta:
                app_label = "migrations"
                apps = new_apps

        class B(A):
            class Meta:
                app_label = "migrations"
                apps = new_apps

        class C(B):
            class Meta:
                app_label = "migrations"
                apps = new_apps

        class D(A):
            class Meta:
                app_label = "migrations"
                apps = new_apps

        class E(B):
            class Meta:
                app_label = "migrations"
                apps = new_apps
                proxy = True

        class F(D):
            class Meta:
                app_label = "migrations"
                apps = new_apps
                proxy = True

        # Make a ProjectState and render it
        project_state = ProjectState()
        project_state.add_model(ModelState.from_model(A))
        project_state.add_model(ModelState.from_model(B))
        project_state.add_model(ModelState.from_model(C))
        project_state.add_model(ModelState.from_model(D))
        project_state.add_model(ModelState.from_model(E))
        project_state.add_model(ModelState.from_model(F))
        final_apps = project_state.apps
        self.assertEqual(len(final_apps.get_models()), 6)

        # Now make an invalid ProjectState and make sure it fails
        project_state = ProjectState()
        project_state.add_model(ModelState.from_model(A))
        project_state.add_model(ModelState.from_model(B))
        project_state.add_model(ModelState.from_model(C))
        project_state.add_model(ModelState.from_model(F))
        with self.assertRaises(InvalidBasesError):
            project_state.apps

    def test_render_unique_app_labels(self):
        """
        The ProjectState render method doesn't raise an
        ImproperlyConfigured exception about unique labels if two dotted app
        names have the same last part.
        """
        class A(models.Model):
            class Meta:
                app_label = "django.contrib.auth"

        class B(models.Model):
            class Meta:
                app_label = "vendor.auth"

        # Make a ProjectState and render it
        project_state = ProjectState()
        project_state.add_model(ModelState.from_model(A))
        project_state.add_model(ModelState.from_model(B))
        self.assertEqual(len(project_state.apps.get_models()), 2)

    def test_reload_related_model_on_non_relational_fields(self):
        """
        The model is reloaded even on changes that are not involved in
        relations. Other models pointing to or from it are also reloaded.
        """
        project_state = ProjectState()
        project_state.apps  # Render project state.
        project_state.add_model(ModelState('migrations', 'A', []))
        project_state.add_model(ModelState('migrations', 'B', [
            ('a', models.ForeignKey('A', models.CASCADE)),
        ]))
        project_state.add_model(ModelState('migrations', 'C', [
            ('b', models.ForeignKey('B', models.CASCADE)),
            ('name', models.TextField()),
        ]))
        project_state.add_model(ModelState('migrations', 'D', [
            ('a', models.ForeignKey('A', models.CASCADE)),
        ]))
        operation = AlterField(
            model_name='C',
            name='name',
            field=models.TextField(blank=True),
        )
        operation.state_forwards('migrations', project_state)
        project_state.reload_model('migrations', 'a', delay=True)
        A = project_state.apps.get_model('migrations.A')
        B = project_state.apps.get_model('migrations.B')
        D = project_state.apps.get_model('migrations.D')
        self.assertIs(B._meta.get_field('a').related_model, A)
        self.assertIs(D._meta.get_field('a').related_model, A)

    def test_reload_model_relationship_consistency(self):
        project_state = ProjectState()
        project_state.add_model(ModelState('migrations', 'A', []))
        project_state.add_model(ModelState('migrations', 'B', [
            ('a', models.ForeignKey('A', models.CASCADE)),
        ]))
        project_state.add_model(ModelState('migrations', 'C', [
            ('b', models.ForeignKey('B', models.CASCADE)),
        ]))
        A = project_state.apps.get_model('migrations.A')
        B = project_state.apps.get_model('migrations.B')
        C = project_state.apps.get_model('migrations.C')
        self.assertEqual([r.related_model for r in A._meta.related_objects], [B])
        self.assertEqual([r.related_model for r in B._meta.related_objects], [C])
        self.assertEqual([r.related_model for r in C._meta.related_objects], [])

        project_state.reload_model('migrations', 'a', delay=True)
        A = project_state.apps.get_model('migrations.A')
        B = project_state.apps.get_model('migrations.B')
        C = project_state.apps.get_model('migrations.C')
        self.assertEqual([r.related_model for r in A._meta.related_objects], [B])
        self.assertEqual([r.related_model for r in B._meta.related_objects], [C])
        self.assertEqual([r.related_model for r in C._meta.related_objects], [])

    def test_add_relations(self):
        """
        #24573 - Adding relations to existing models should reload the
        referenced models too.
        """
        new_apps = Apps()

        class A(models.Model):
            class Meta:
                app_label = 'something'
                apps = new_apps

        class B(A):
            class Meta:
                app_label = 'something'
                apps = new_apps

        class C(models.Model):
            class Meta:
                app_label = 'something'
                apps = new_apps

        project_state = ProjectState()
        project_state.add_model(ModelState.from_model(A))
        project_state.add_model(ModelState.from_model(B))
        project_state.add_model(ModelState.from_model(C))

        project_state.apps  # We need to work with rendered models

        old_state = project_state.clone()
        model_a_old = old_state.apps.get_model('something', 'A')
        model_b_old = old_state.apps.get_model('something', 'B')
        model_c_old = old_state.apps.get_model('something', 'C')
        # The relations between the old models are correct
        self.assertIs(model_a_old._meta.get_field('b').related_model, model_b_old)
        self.assertIs(model_b_old._meta.get_field('a_ptr').related_model, model_a_old)

        operation = AddField('c', 'to_a', models.OneToOneField(
            'something.A',
            models.CASCADE,
            related_name='from_c',
        ))
        operation.state_forwards('something', project_state)
        model_a_new = project_state.apps.get_model('something', 'A')
        model_b_new = project_state.apps.get_model('something', 'B')
        model_c_new = project_state.apps.get_model('something', 'C')

        # All models have changed
        self.assertIsNot(model_a_old, model_a_new)
        self.assertIsNot(model_b_old, model_b_new)
        self.assertIsNot(model_c_old, model_c_new)
        # The relations between the old models still hold
        self.assertIs(model_a_old._meta.get_field('b').related_model, model_b_old)
        self.assertIs(model_b_old._meta.get_field('a_ptr').related_model, model_a_old)
        # The relations between the new models correct
        self.assertIs(model_a_new._meta.get_field('b').related_model, model_b_new)
        self.assertIs(model_b_new._meta.get_field('a_ptr').related_model, model_a_new)
        self.assertIs(model_a_new._meta.get_field('from_c').related_model, model_c_new)
        self.assertIs(model_c_new._meta.get_field('to_a').related_model, model_a_new)

    def test_remove_relations(self):
        """
        #24225 - Relations between models are updated while
        remaining the relations and references for models of an old state.
        """
        new_apps = Apps()

        class A(models.Model):
            class Meta:
                app_label = "something"
                apps = new_apps

        class B(models.Model):
            to_a = models.ForeignKey(A, models.CASCADE)

            class Meta:
                app_label = "something"
                apps = new_apps

        def get_model_a(state):
            return [mod for mod in state.apps.get_models() if mod._meta.model_name == 'a'][0]

        project_state = ProjectState()
        project_state.add_model(ModelState.from_model(A))
        project_state.add_model(ModelState.from_model(B))
        self.assertEqual(len(get_model_a(project_state)._meta.related_objects), 1)
        old_state = project_state.clone()

        operation = RemoveField("b", "to_a")
        operation.state_forwards("something", project_state)
        # Model from old_state still has the relation
        model_a_old = get_model_a(old_state)
        model_a_new = get_model_a(project_state)
        self.assertIsNot(model_a_old, model_a_new)
        self.assertEqual(len(model_a_old._meta.related_objects), 1)
        self.assertEqual(len(model_a_new._meta.related_objects), 0)

        # Same test for deleted model
        project_state = ProjectState()
        project_state.add_model(ModelState.from_model(A))
        project_state.add_model(ModelState.from_model(B))
        old_state = project_state.clone()

        operation = DeleteModel("b")
        operation.state_forwards("something", project_state)
        model_a_old = get_model_a(old_state)
        model_a_new = get_model_a(project_state)
        self.assertIsNot(model_a_old, model_a_new)
        self.assertEqual(len(model_a_old._meta.related_objects), 1)
        self.assertEqual(len(model_a_new._meta.related_objects), 0)

    def test_self_relation(self):
        """
        #24513 - Modifying an object pointing to itself would cause it to be
        rendered twice and thus breaking its related M2M through objects.
        """
        class A(models.Model):
            to_a = models.ManyToManyField('something.A', symmetrical=False)

            class Meta:
                app_label = "something"

        def get_model_a(state):
            return [mod for mod in state.apps.get_models() if mod._meta.model_name == 'a'][0]

        project_state = ProjectState()
        project_state.add_model(ModelState.from_model(A))
        self.assertEqual(len(get_model_a(project_state)._meta.related_objects), 1)
        old_state = project_state.clone()

        operation = AlterField(
            model_name="a",
            name="to_a",
            field=models.ManyToManyField("something.A", symmetrical=False, blank=True)
        )
        # At this point the model would be rendered twice causing its related
        # M2M through objects to point to an old copy and thus breaking their
        # attribute lookup.
        operation.state_forwards("something", project_state)

        model_a_old = get_model_a(old_state)
        model_a_new = get_model_a(project_state)
        self.assertIsNot(model_a_old, model_a_new)

        # The old model's _meta is still consistent
        field_to_a_old = model_a_old._meta.get_field("to_a")
        self.assertEqual(field_to_a_old.m2m_field_name(), "from_a")
        self.assertEqual(field_to_a_old.m2m_reverse_field_name(), "to_a")
        self.assertIs(field_to_a_old.related_model, model_a_old)
        self.assertIs(field_to_a_old.remote_field.through._meta.get_field('to_a').related_model, model_a_old)
        self.assertIs(field_to_a_old.remote_field.through._meta.get_field('from_a').related_model, model_a_old)

        # The new model's _meta is still consistent
        field_to_a_new = model_a_new._meta.get_field("to_a")
        self.assertEqual(field_to_a_new.m2m_field_name(), "from_a")
        self.assertEqual(field_to_a_new.m2m_reverse_field_name(), "to_a")
        self.assertIs(field_to_a_new.related_model, model_a_new)
        self.assertIs(field_to_a_new.remote_field.through._meta.get_field('to_a').related_model, model_a_new)
        self.assertIs(field_to_a_new.remote_field.through._meta.get_field('from_a').related_model, model_a_new)

    def test_equality(self):
        """
        == and != are implemented correctly.
        """
        # Test two things that should be equal
        project_state = ProjectState()
        project_state.add_model(ModelState(
            "migrations",
            "Tag",
            [
                ("id", models.AutoField(primary_key=True)),
                ("name", models.CharField(max_length=100)),
                ("hidden", models.BooleanField()),
            ],
            {},
            None,
        ))
        project_state.apps  # Fill the apps cached property
        other_state = project_state.clone()
        self.assertEqual(project_state, project_state)
        self.assertEqual(project_state, other_state)
        self.assertIs(project_state != project_state, False)
        self.assertIs(project_state != other_state, False)
        self.assertNotEqual(project_state.apps, other_state.apps)

        # Make a very small change (max_len 99) and see if that affects it
        project_state = ProjectState()
        project_state.add_model(ModelState(
            "migrations",
            "Tag",
            [
                ("id", models.AutoField(primary_key=True)),
                ("name", models.CharField(max_length=99)),
                ("hidden", models.BooleanField()),
            ],
            {},
            None,
        ))
        self.assertNotEqual(project_state, other_state)
        self.assertIs(project_state == other_state, False)

    def test_dangling_references_throw_error(self):
        new_apps = Apps()

        class Author(models.Model):
            name = models.TextField()

            class Meta:
                app_label = "migrations"
                apps = new_apps

        class Publisher(models.Model):
            name = models.TextField()

            class Meta:
                app_label = "migrations"
                apps = new_apps

        class Book(models.Model):
            author = models.ForeignKey(Author, models.CASCADE)
            publisher = models.ForeignKey(Publisher, models.CASCADE)

            class Meta:
                app_label = "migrations"
                apps = new_apps

        class Magazine(models.Model):
            authors = models.ManyToManyField(Author)

            class Meta:
                app_label = "migrations"
                apps = new_apps

        # Make a valid ProjectState and render it
        project_state = ProjectState()
        project_state.add_model(ModelState.from_model(Author))
        project_state.add_model(ModelState.from_model(Publisher))
        project_state.add_model(ModelState.from_model(Book))
        project_state.add_model(ModelState.from_model(Magazine))
        self.assertEqual(len(project_state.apps.get_models()), 4)

        # now make an invalid one with a ForeignKey
        project_state = ProjectState()
        project_state.add_model(ModelState.from_model(Book))
        msg = (
            "The field migrations.Book.author was declared with a lazy reference "
            "to 'migrations.author', but app 'migrations' doesn't provide model 'author'.\n"
            "The field migrations.Book.publisher was declared with a lazy reference "
            "to 'migrations.publisher', but app 'migrations' doesn't provide model 'publisher'."
        )
        with self.assertRaisesMessage(ValueError, msg):
            project_state.apps

        # And another with ManyToManyField.
        project_state = ProjectState()
        project_state.add_model(ModelState.from_model(Magazine))
        msg = (
            "The field migrations.Magazine.authors was declared with a lazy reference "
            "to 'migrations.author\', but app 'migrations' doesn't provide model 'author'.\n"
            "The field migrations.Magazine_authors.author was declared with a lazy reference "
            "to \'migrations.author\', but app 'migrations' doesn't provide model 'author'."
        )
        with self.assertRaisesMessage(ValueError, msg):
            project_state.apps

        # And now with multiple models and multiple fields.
        project_state.add_model(ModelState.from_model(Book))
        msg = (
            "The field migrations.Book.author was declared with a lazy reference "
            "to 'migrations.author', but app 'migrations' doesn't provide model 'author'.\n"
            "The field migrations.Book.publisher was declared with a lazy reference "
            "to 'migrations.publisher', but app 'migrations' doesn't provide model 'publisher'.\n"
            "The field migrations.Magazine.authors was declared with a lazy reference "
            "to 'migrations.author', but app 'migrations' doesn't provide model 'author'.\n"
            "The field migrations.Magazine_authors.author was declared with a lazy reference "
            "to 'migrations.author', but app 'migrations' doesn't provide model 'author'."
        )
        with self.assertRaisesMessage(ValueError, msg):
            project_state.apps

    def test_reference_mixed_case_app_label(self):
        new_apps = Apps()

        class Author(models.Model):
            class Meta:
                app_label = 'MiXedCase_migrations'
                apps = new_apps

        class Book(models.Model):
            author = models.ForeignKey(Author, models.CASCADE)

            class Meta:
                app_label = 'MiXedCase_migrations'
                apps = new_apps

        class Magazine(models.Model):
            authors = models.ManyToManyField(Author)

            class Meta:
                app_label = 'MiXedCase_migrations'
                apps = new_apps

        project_state = ProjectState()
        project_state.add_model(ModelState.from_model(Author))
        project_state.add_model(ModelState.from_model(Book))
        project_state.add_model(ModelState.from_model(Magazine))
        self.assertEqual(len(project_state.apps.get_models()), 3)

    def test_real_apps(self):
        """
        Including real apps can resolve dangling FK errors.
        This test relies on the fact that contenttypes is always loaded.
        """
        new_apps = Apps()

        class TestModel(models.Model):
            ct = models.ForeignKey("contenttypes.ContentType", models.CASCADE)

            class Meta:
                app_label = "migrations"
                apps = new_apps

        # If we just stick it into an empty state it should fail
        project_state = ProjectState()
        project_state.add_model(ModelState.from_model(TestModel))
        with self.assertRaises(ValueError):
            project_state.apps

        # If we include the real app it should succeed
        project_state = ProjectState(real_apps=["contenttypes"])
        project_state.add_model(ModelState.from_model(TestModel))
        rendered_state = project_state.apps
        self.assertEqual(
            len([x for x in rendered_state.get_models() if x._meta.app_label == "migrations"]),
            1,
        )

    def test_ignore_order_wrt(self):
        """
        Makes sure ProjectState doesn't include OrderWrt fields when
        making from existing models.
        """
        new_apps = Apps()

        class Author(models.Model):
            name = models.TextField()

            class Meta:
                app_label = "migrations"
                apps = new_apps

        class Book(models.Model):
            author = models.ForeignKey(Author, models.CASCADE)

            class Meta:
                app_label = "migrations"
                apps = new_apps
                order_with_respect_to = "author"

        # Make a valid ProjectState and render it
        project_state = ProjectState()
        project_state.add_model(ModelState.from_model(Author))
        project_state.add_model(ModelState.from_model(Book))
        self.assertEqual(
            list(project_state.models['migrations', 'book'].fields),
            ["id", "author"],
        )

    def test_manager_refer_correct_model_version(self):
        """
        #24147 - Managers refer to the correct version of a
        historical model
        """
        project_state = ProjectState()
        project_state.add_model(ModelState(
            app_label="migrations",
            name="Tag",
            fields=[
                ("id", models.AutoField(primary_key=True)),
                ("hidden", models.BooleanField()),
            ],
            managers=[
                ('food_mgr', FoodManager('a', 'b')),
                ('food_qs', FoodQuerySet.as_manager()),
            ]
        ))

        old_model = project_state.apps.get_model('migrations', 'tag')

        new_state = project_state.clone()
        operation = RemoveField("tag", "hidden")
        operation.state_forwards("migrations", new_state)

        new_model = new_state.apps.get_model('migrations', 'tag')

        self.assertIsNot(old_model, new_model)
        self.assertIs(old_model, old_model.food_mgr.model)
        self.assertIs(old_model, old_model.food_qs.model)
        self.assertIs(new_model, new_model.food_mgr.model)
        self.assertIs(new_model, new_model.food_qs.model)
        self.assertIsNot(old_model.food_mgr, new_model.food_mgr)
        self.assertIsNot(old_model.food_qs, new_model.food_qs)
        self.assertIsNot(old_model.food_mgr.model, new_model.food_mgr.model)
        self.assertIsNot(old_model.food_qs.model, new_model.food_qs.model)

    def test_choices_iterator(self):
        """
        #24483 - ProjectState.from_apps should not destructively consume
        Field.choices iterators.
        """
        new_apps = Apps(["migrations"])
        choices = [('a', 'A'), ('b', 'B')]

        class Author(models.Model):
            name = models.CharField(max_length=255)
            choice = models.CharField(max_length=255, choices=iter(choices))

            class Meta:
                app_label = "migrations"
                apps = new_apps

        ProjectState.from_apps(new_apps)
        choices_field = Author._meta.get_field('choice')
        self.assertEqual(list(choices_field.choices), choices)


class ModelStateTests(SimpleTestCase):
    def test_custom_model_base(self):
        state = ModelState.from_model(ModelWithCustomBase)
        self.assertEqual(state.bases, (models.Model,))

    def test_bound_field_sanity_check(self):
        field = models.CharField(max_length=1)
        field.model = models.Model
        with self.assertRaisesMessage(ValueError, 'ModelState.fields cannot be bound to a model - "field" is.'):
            ModelState('app', 'Model', [('field', field)])

    def test_sanity_check_to(self):
        field = models.ForeignKey(UnicodeModel, models.CASCADE)
        with self.assertRaisesMessage(
            ValueError,
            'ModelState.fields cannot refer to a model class - "field.to" does. '
            'Use a string reference instead.'
        ):
            ModelState('app', 'Model', [('field', field)])

    def test_sanity_check_through(self):
        field = models.ManyToManyField('UnicodeModel')
        field.remote_field.through = UnicodeModel
        with self.assertRaisesMessage(
            ValueError,
            'ModelState.fields cannot refer to a model class - "field.through" does. '
            'Use a string reference instead.'
        ):
            ModelState('app', 'Model', [('field', field)])

    def test_sanity_index_name(self):
        field = models.IntegerField()
        options = {'indexes': [models.Index(fields=['field'])]}
        msg = (
            "Indexes passed to ModelState require a name attribute. <Index: "
            "fields=['field']> doesn't have one."
        )
        with self.assertRaisesMessage(ValueError, msg):
            ModelState('app', 'Model', [('field', field)], options=options)

    def test_fields_immutability(self):
        """
        Rendering a model state doesn't alter its internal fields.
        """
        apps = Apps()
        field = models.CharField(max_length=1)
        state = ModelState('app', 'Model', [('name', field)])
        Model = state.render(apps)
        self.assertNotEqual(Model._meta.get_field('name'), field)

    def test_repr(self):
        field = models.CharField(max_length=1)
        state = ModelState('app', 'Model', [('name', field)], bases=['app.A', 'app.B', 'app.C'])
        self.assertEqual(repr(state), "<ModelState: 'app.Model'>")

        project_state = ProjectState()
        project_state.add_model(state)
        with self.assertRaisesMessage(InvalidBasesError, "Cannot resolve bases for [<ModelState: 'app.Model'>]"):
            project_state.apps

    def test_fields_ordering_equality(self):
        state = ModelState(
            'migrations',
            'Tag',
            [
                ('id', models.AutoField(primary_key=True)),
                ('name', models.CharField(max_length=100)),
                ('hidden', models.BooleanField()),
            ],
        )
        reordered_state = ModelState(
            'migrations',
            'Tag',
            [
                ('id', models.AutoField(primary_key=True)),
                # Purposely re-ordered.
                ('hidden', models.BooleanField()),
                ('name', models.CharField(max_length=100)),
            ],
        )
        self.assertEqual(state, reordered_state)

    @override_settings(TEST_SWAPPABLE_MODEL='migrations.SomeFakeModel')
    def test_create_swappable(self):
        """
        Tests making a ProjectState from an Apps with a swappable model
        """
        new_apps = Apps(['migrations'])

        class Author(models.Model):
            name = models.CharField(max_length=255)
            bio = models.TextField()
            age = models.IntegerField(blank=True, null=True)

            class Meta:
                app_label = 'migrations'
                apps = new_apps
                swappable = 'TEST_SWAPPABLE_MODEL'

        author_state = ModelState.from_model(Author)
        self.assertEqual(author_state.app_label, 'migrations')
        self.assertEqual(author_state.name, 'Author')
        self.assertEqual(list(author_state.fields), ['id', 'name', 'bio', 'age'])
        self.assertEqual(author_state.fields['name'].max_length, 255)
        self.assertIs(author_state.fields['bio'].null, False)
        self.assertIs(author_state.fields['age'].null, True)
        self.assertEqual(author_state.options, {'swappable': 'TEST_SWAPPABLE_MODEL', 'indexes': [], "constraints": []})
        self.assertEqual(author_state.bases, (models.Model,))
        self.assertEqual(author_state.managers, [])

    @override_settings(TEST_SWAPPABLE_MODEL='migrations.SomeFakeModel')
    def test_create_swappable_from_abstract(self):
        """
        A swappable model inheriting from a hierarchy:
        concrete -> abstract -> concrete.
        """
        new_apps = Apps(['migrations'])

        class SearchableLocation(models.Model):
            keywords = models.CharField(max_length=256)

            class Meta:
                app_label = 'migrations'
                apps = new_apps

        class Station(SearchableLocation):
            name = models.CharField(max_length=128)

            class Meta:
                abstract = True

        class BusStation(Station):
            bus_routes = models.CharField(max_length=128)
            inbound = models.BooleanField(default=False)

            class Meta(Station.Meta):
                app_label = 'migrations'
                apps = new_apps
                swappable = 'TEST_SWAPPABLE_MODEL'

        station_state = ModelState.from_model(BusStation)
        self.assertEqual(station_state.app_label, 'migrations')
        self.assertEqual(station_state.name, 'BusStation')
        self.assertEqual(
            list(station_state.fields),
            ['searchablelocation_ptr', 'name', 'bus_routes', 'inbound']
        )
        self.assertEqual(station_state.fields['name'].max_length, 128)
        self.assertIs(station_state.fields['bus_routes'].null, False)
        self.assertEqual(
            station_state.options,
            {'abstract': False, 'swappable': 'TEST_SWAPPABLE_MODEL', 'indexes': [], 'constraints': []}
        )
        self.assertEqual(station_state.bases, ('migrations.searchablelocation',))
        self.assertEqual(station_state.managers, [])

    @override_settings(TEST_SWAPPABLE_MODEL='migrations.SomeFakeModel')
    def test_custom_manager_swappable(self):
        """
        Tests making a ProjectState from unused models with custom managers
        """
        new_apps = Apps(['migrations'])

        class Food(models.Model):

            food_mgr = FoodManager('a', 'b')
            food_qs = FoodQuerySet.as_manager()
            food_no_mgr = NoMigrationFoodManager('x', 'y')

            class Meta:
                app_label = "migrations"
                apps = new_apps
                swappable = 'TEST_SWAPPABLE_MODEL'

        food_state = ModelState.from_model(Food)

        # The default manager is used in migrations
        self.assertEqual([name for name, mgr in food_state.managers], ['food_mgr'])
        self.assertEqual(food_state.managers[0][1].args, ('a', 'b', 1, 2))

    @isolate_apps('migrations', 'django.contrib.contenttypes')
    def test_order_with_respect_to_private_field(self):
        class PrivateFieldModel(models.Model):
            content_type = models.ForeignKey('contenttypes.ContentType', models.CASCADE)
            object_id = models.PositiveIntegerField()
            private = GenericForeignKey()

            class Meta:
                order_with_respect_to = 'private'

        state = ModelState.from_model(PrivateFieldModel)
        self.assertNotIn('order_with_respect_to', state.options)

    @isolate_apps('migrations')
    def test_abstract_model_children_inherit_indexes(self):
        class Abstract(models.Model):
            name = models.CharField(max_length=50)

            class Meta:
                app_label = 'migrations'
                abstract = True
                indexes = [models.Index(fields=['name'])]

        class Child1(Abstract):
            pass

        class Child2(Abstract):
            pass

        child1_state = ModelState.from_model(Child1)
        child2_state = ModelState.from_model(Child2)
        index_names = [index.name for index in child1_state.options['indexes']]
        self.assertEqual(index_names, ['migrations__name_b0afd7_idx'])
        index_names = [index.name for index in child2_state.options['indexes']]
        self.assertEqual(index_names, ['migrations__name_016466_idx'])

        # Modifying the state doesn't modify the index on the model.
        child1_state.options['indexes'][0].name = 'bar'
        self.assertEqual(Child1._meta.indexes[0].name, 'migrations__name_b0afd7_idx')

    @isolate_apps('migrations')
    def test_explicit_index_name(self):
        class TestModel(models.Model):
            name = models.CharField(max_length=50)

            class Meta:
                app_label = 'migrations'
                indexes = [models.Index(fields=['name'], name='foo_idx')]

        model_state = ModelState.from_model(TestModel)
        index_names = [index.name for index in model_state.options['indexes']]
        self.assertEqual(index_names, ['foo_idx'])

    @isolate_apps('migrations')
    def test_from_model_constraints(self):
        class ModelWithConstraints(models.Model):
            size = models.IntegerField()

            class Meta:
                constraints = [models.CheckConstraint(check=models.Q(size__gt=1), name='size_gt_1')]

        state = ModelState.from_model(ModelWithConstraints)
        model_constraints = ModelWithConstraints._meta.constraints
        state_constraints = state.options['constraints']
        self.assertEqual(model_constraints, state_constraints)
        self.assertIsNot(model_constraints, state_constraints)
        self.assertIsNot(model_constraints[0], state_constraints[0])


class RelatedModelsTests(SimpleTestCase):

    def setUp(self):
        self.apps = Apps(['migrations.related_models_app'])

    def create_model(self, name, foreign_keys=[], bases=(), abstract=False, proxy=False):
        test_name = 'related_models_app'
        assert not (abstract and proxy)
        meta_contents = {
            'abstract': abstract,
            'app_label': test_name,
            'apps': self.apps,
            'proxy': proxy,
        }
        meta = type("Meta", (), meta_contents)
        if not bases:
            bases = (models.Model,)
        body = {
            'Meta': meta,
            '__module__': "__fake__",
        }
        fname_base = fname = '%s_%%d' % name.lower()
        for i, fk in enumerate(foreign_keys, 1):
            fname = fname_base % i
            body[fname] = fk
        return type(name, bases, body)

    def assertRelated(self, model, needle):
        self.assertEqual(
            get_related_models_recursive(model),
            {(n._meta.app_label, n._meta.model_name) for n in needle},
        )

    def test_unrelated(self):
        A = self.create_model("A")
        B = self.create_model("B")
        self.assertRelated(A, [])
        self.assertRelated(B, [])

    def test_direct_fk(self):
        A = self.create_model("A", foreign_keys=[models.ForeignKey('B', models.CASCADE)])
        B = self.create_model("B")
        self.assertRelated(A, [B])
        self.assertRelated(B, [A])

    def test_direct_hidden_fk(self):
        A = self.create_model("A", foreign_keys=[models.ForeignKey('B', models.CASCADE, related_name='+')])
        B = self.create_model("B")
        self.assertRelated(A, [B])
        self.assertRelated(B, [A])

    def test_fk_through_proxy(self):
        A = self.create_model("A")
        B = self.create_model("B", bases=(A,), proxy=True)
        C = self.create_model("C", bases=(B,), proxy=True)
        D = self.create_model("D", foreign_keys=[models.ForeignKey('C', models.CASCADE)])
        self.assertRelated(A, [B, C, D])
        self.assertRelated(B, [A, C, D])
        self.assertRelated(C, [A, B, D])
        self.assertRelated(D, [A, B, C])

    def test_nested_fk(self):
        A = self.create_model("A", foreign_keys=[models.ForeignKey('B', models.CASCADE)])
        B = self.create_model("B", foreign_keys=[models.ForeignKey('C', models.CASCADE)])
        C = self.create_model("C")
        self.assertRelated(A, [B, C])
        self.assertRelated(B, [A, C])
        self.assertRelated(C, [A, B])

    def test_two_sided(self):
        A = self.create_model("A", foreign_keys=[models.ForeignKey('B', models.CASCADE)])
        B = self.create_model("B", foreign_keys=[models.ForeignKey('A', models.CASCADE)])
        self.assertRelated(A, [B])
        self.assertRelated(B, [A])

    def test_circle(self):
        A = self.create_model("A", foreign_keys=[models.ForeignKey('B', models.CASCADE)])
        B = self.create_model("B", foreign_keys=[models.ForeignKey('C', models.CASCADE)])
        C = self.create_model("C", foreign_keys=[models.ForeignKey('A', models.CASCADE)])
        self.assertRelated(A, [B, C])
        self.assertRelated(B, [A, C])
        self.assertRelated(C, [A, B])

    def test_base(self):
        A = self.create_model("A")
        B = self.create_model("B", bases=(A,))
        self.assertRelated(A, [B])
        self.assertRelated(B, [A])

    def test_nested_base(self):
        A = self.create_model("A")
        B = self.create_model("B", bases=(A,))
        C = self.create_model("C", bases=(B,))
        self.assertRelated(A, [B, C])
        self.assertRelated(B, [A, C])
        self.assertRelated(C, [A, B])

    def test_multiple_bases(self):
        A = self.create_model("A")
        B = self.create_model("B")
        C = self.create_model("C", bases=(A, B,))
        self.assertRelated(A, [B, C])
        self.assertRelated(B, [A, C])
        self.assertRelated(C, [A, B])

    def test_multiple_nested_bases(self):
        A = self.create_model("A")
        B = self.create_model("B")
        C = self.create_model("C", bases=(A, B,))
        D = self.create_model("D")
        E = self.create_model("E", bases=(D,))
        F = self.create_model("F", bases=(C, E,))
        Y = self.create_model("Y")
        Z = self.create_model("Z", bases=(Y,))
        self.assertRelated(A, [B, C, D, E, F])
        self.assertRelated(B, [A, C, D, E, F])
        self.assertRelated(C, [A, B, D, E, F])
        self.assertRelated(D, [A, B, C, E, F])
        self.assertRelated(E, [A, B, C, D, F])
        self.assertRelated(F, [A, B, C, D, E])
        self.assertRelated(Y, [Z])
        self.assertRelated(Z, [Y])

    def test_base_to_base_fk(self):
        A = self.create_model("A", foreign_keys=[models.ForeignKey('Y', models.CASCADE)])
        B = self.create_model("B", bases=(A,))
        Y = self.create_model("Y")
        Z = self.create_model("Z", bases=(Y,))
        self.assertRelated(A, [B, Y, Z])
        self.assertRelated(B, [A, Y, Z])
        self.assertRelated(Y, [A, B, Z])
        self.assertRelated(Z, [A, B, Y])

    def test_base_to_subclass_fk(self):
        A = self.create_model("A", foreign_keys=[models.ForeignKey('Z', models.CASCADE)])
        B = self.create_model("B", bases=(A,))
        Y = self.create_model("Y")
        Z = self.create_model("Z", bases=(Y,))
        self.assertRelated(A, [B, Y, Z])
        self.assertRelated(B, [A, Y, Z])
        self.assertRelated(Y, [A, B, Z])
        self.assertRelated(Z, [A, B, Y])

    def test_direct_m2m(self):
        A = self.create_model("A", foreign_keys=[models.ManyToManyField('B')])
        B = self.create_model("B")
        self.assertRelated(A, [A.a_1.rel.through, B])
        self.assertRelated(B, [A, A.a_1.rel.through])

    def test_direct_m2m_self(self):
        A = self.create_model("A", foreign_keys=[models.ManyToManyField('A')])
        self.assertRelated(A, [A.a_1.rel.through])

    def test_intermediate_m2m_self(self):
        A = self.create_model("A", foreign_keys=[models.ManyToManyField('A', through='T')])
        T = self.create_model("T", foreign_keys=[
            models.ForeignKey('A', models.CASCADE),
            models.ForeignKey('A', models.CASCADE),
        ])
        self.assertRelated(A, [T])
        self.assertRelated(T, [A])

    def test_intermediate_m2m(self):
        A = self.create_model("A", foreign_keys=[models.ManyToManyField('B', through='T')])
        B = self.create_model("B")
        T = self.create_model("T", foreign_keys=[
            models.ForeignKey('A', models.CASCADE),
            models.ForeignKey('B', models.CASCADE),
        ])
        self.assertRelated(A, [B, T])
        self.assertRelated(B, [A, T])
        self.assertRelated(T, [A, B])

    def test_intermediate_m2m_extern_fk(self):
        A = self.create_model("A", foreign_keys=[models.ManyToManyField('B', through='T')])
        B = self.create_model("B")
        Z = self.create_model("Z")
        T = self.create_model("T", foreign_keys=[
            models.ForeignKey('A', models.CASCADE),
            models.ForeignKey('B', models.CASCADE),
            models.ForeignKey('Z', models.CASCADE),
        ])
        self.assertRelated(A, [B, T, Z])
        self.assertRelated(B, [A, T, Z])
        self.assertRelated(T, [A, B, Z])
        self.assertRelated(Z, [A, B, T])

    def test_intermediate_m2m_base(self):
        A = self.create_model("A", foreign_keys=[models.ManyToManyField('B', through='T')])
        B = self.create_model("B")
        S = self.create_model("S")
        T = self.create_model("T", foreign_keys=[
            models.ForeignKey('A', models.CASCADE),
            models.ForeignKey('B', models.CASCADE),
        ], bases=(S,))
        self.assertRelated(A, [B, S, T])
        self.assertRelated(B, [A, S, T])
        self.assertRelated(S, [A, B, T])
        self.assertRelated(T, [A, B, S])

    def test_generic_fk(self):
        A = self.create_model("A", foreign_keys=[
            models.ForeignKey('B', models.CASCADE),
            GenericForeignKey(),
        ])
        B = self.create_model("B", foreign_keys=[
            models.ForeignKey('C', models.CASCADE),
        ])
        self.assertRelated(A, [B])
        self.assertRelated(B, [A])

    def test_abstract_base(self):
        A = self.create_model("A", abstract=True)
        B = self.create_model("B", bases=(A,))
        self.assertRelated(A, [B])
        self.assertRelated(B, [])

    def test_nested_abstract_base(self):
        A = self.create_model("A", abstract=True)
        B = self.create_model("B", bases=(A,), abstract=True)
        C = self.create_model("C", bases=(B,))
        self.assertRelated(A, [B, C])
        self.assertRelated(B, [C])
        self.assertRelated(C, [])

    def test_proxy_base(self):
        A = self.create_model("A")
        B = self.create_model("B", bases=(A,), proxy=True)
        self.assertRelated(A, [B])
        self.assertRelated(B, [])

    def test_nested_proxy_base(self):
        A = self.create_model("A")
        B = self.create_model("B", bases=(A,), proxy=True)
        C = self.create_model("C", bases=(B,), proxy=True)
        self.assertRelated(A, [B, C])
        self.assertRelated(B, [C])
        self.assertRelated(C, [])

    def test_multiple_mixed_bases(self):
        A = self.create_model("A", abstract=True)
        M = self.create_model("M")
        P = self.create_model("P")
        Q = self.create_model("Q", bases=(P,), proxy=True)
        Z = self.create_model("Z", bases=(A, M, Q))
        # M has a pointer O2O field p_ptr to P
        self.assertRelated(A, [M, P, Q, Z])
        self.assertRelated(M, [P, Q, Z])
        self.assertRelated(P, [M, Q, Z])
        self.assertRelated(Q, [M, P, Z])
        self.assertRelated(Z, [M, P, Q])