Python django.db.models.CASCADE Examples

def ask_remove_enum_values(self, db_type, values):
        """ How to treat records with deleted enum values. """
        # Ordered ensures
        choices = [
            (models.CASCADE, "Cascade - Delete records with removed values"),
            (models.PROTECT, "Protect - Block migrations if records contain removed values"),
            (models.SET_NULL, "Set NULL - Set value to NULL"),
            (models.SET_DEFAULT, "Set default - Set value to field default"),
            (models.SET, "Set value - Provide a one off default now"),
            (models.DO_NOTHING, "Do nothing - Consistency must be handled elsewhere"),
            (None, "Leave it to field definitions")]
        choice, _ = choices[self._choice_input(
            "Enum {db_type} has had {values} removed, "
            "existing records may need to be updated. "
            "Override update behaviour or do nothing and follow field behaviour.".format(
                db_type=db_type,
                values=values),
            [q for (k, q) in choices]) - 1]
        if choice == models.SET:
            return models.SET(self._ask_default())
        return choice 

def test_parental_key_checks_clusterable_model(self):
        from django.core import checks
        from django.db import models
        from modelcluster.fields import ParentalKey

        class Instrument(models.Model):
            # Oops, BandMember is not a Clusterable model
            member = ParentalKey(BandMember, on_delete=models.CASCADE)

            class Meta:
                # Prevent Django from thinking this is in the database
                # This shouldn't affect the test
                abstract = True

        # Check for error
        errors = Instrument.check()
        self.assertEqual(1, len(errors))

        # Check the error itself
        error = errors[0]
        self.assertIsInstance(error, checks.Error)
        self.assertEqual(error.id, 'modelcluster.E001')
        self.assertEqual(error.obj, Instrument.member.field)
        self.assertEqual(error.msg, 'ParentalKey must point to a subclass of ClusterableModel.')
        self.assertEqual(error.hint, 'Change tests.BandMember into a ClusterableModel or use a ForeignKey instead.') 

def test_relationship_model_missing_foreign_key(self):
        class Person(models.Model):
            pass

        class Group(models.Model):
            members = models.ManyToManyField('Person', through="InvalidRelationship")

        class InvalidRelationship(models.Model):
            group = models.ForeignKey(Group, models.CASCADE)
            # No foreign key to Person

        field = Group._meta.get_field('members')
        self.assertEqual(field.check(from_model=Group), [
            Error(
                "The model is used as an intermediate model by "
                "'invalid_models_tests.Group.members', but it does not have "
                "a foreign key to 'Group' or 'Person'.",
                obj=InvalidRelationship,
                id='fields.E336',
            ),
        ]) 

def __init__(self, to, object_id_field='object_id', content_type_field='content_type',
            for_concrete_model=True, related_query_name=None, limit_choices_to=None, **kwargs):
        kwargs['rel'] = self.rel_class(
            self, to,
            related_query_name=related_query_name,
            limit_choices_to=limit_choices_to,
        )

        kwargs['blank'] = True
        kwargs['on_delete'] = models.CASCADE
        kwargs['editable'] = False
        kwargs['serialize'] = False

        # This construct is somewhat of an abuse of ForeignObject. This field
        # represents a relation from pk to object_id field. But, this relation
        # isn't direct, the join is generated reverse along foreign key. So,
        # the from_field is object_id field, to_field is pk because of the
        # reverse join.
        super(GenericRelation, self).__init__(
            to, from_fields=[object_id_field], to_fields=[], **kwargs)

        self.object_id_field_name = object_id_field
        self.content_type_field_name = content_type_field
        self.for_concrete_model = for_concrete_model 

def test_remove_field_m2m_with_through(self):
        project_state = self.set_up_test_model("test_rmflmmwt", second_model=True)

        self.assertTableNotExists("test_rmflmmwt_ponystables")
        project_state = self.apply_operations("test_rmflmmwt", project_state, operations=[
            migrations.CreateModel("PonyStables", fields=[
                ("pony", models.ForeignKey('test_rmflmmwt.Pony', models.CASCADE)),
                ("stable", models.ForeignKey('test_rmflmmwt.Stable', models.CASCADE)),
            ]),
            migrations.AddField(
                "Pony", "stables",
                models.ManyToManyField("Stable", related_name="ponies", through='test_rmflmmwt.PonyStables')
            )
        ])
        self.assertTableExists("test_rmflmmwt_ponystables")

        operations = [migrations.RemoveField("Pony", "stables"), migrations.DeleteModel("PonyStables")]
        self.apply_operations("test_rmflmmwt", project_state, operations=operations) 

def test_create_model_and_unique_together(self):
        author = ModelState("otherapp", "Author", [
            ("id", models.AutoField(primary_key=True)),
            ("name", models.CharField(max_length=200)),
        ])
        book_with_author = ModelState("otherapp", "Book", [
            ("id", models.AutoField(primary_key=True)),
            ("author", models.ForeignKey("otherapp.Author", models.CASCADE)),
            ("title", models.CharField(max_length=200)),
        ], {
            "index_together": {("title", "author")},
            "unique_together": {("title", "author")},
        })
        changes = self.get_changes([self.book_with_no_author], [author, book_with_author])
        # Right number of migrations?
        self.assertEqual(len(changes['otherapp']), 1)
        # Right number of actions?
        migration = changes['otherapp'][0]
        self.assertEqual(len(migration.operations), 4)
        # Right actions order?
        self.assertOperationTypes(
            changes, 'otherapp', 0,
            ['CreateModel', 'AddField', 'AlterUniqueTogether', 'AlterIndexTogether']
        ) 

def delete(self, *args, **kwargs):
        # Clear delta history. Deltas can reference WfModules: if we don't
        # clear the deltas, Django may decide to CASCADE to WfModule first and
        # we'll raise a ProtectedError.
        self.clear_deltas()

        # Clear all minio data. We _should_ clear it in pre-delete hooks on
        # StoredObject, UploadedFile, etc.; but [2019-06-03, adamhooper] the
        # database is inconsistent and Django is hard to use so new bugs may
        # crop up anyway.
        #
        # [2019-06-03, adamhooper] hooks never work in ORMs. Better would be
        # to make `delete()` a controller method, not a funky mishmash of
        # Django-ORM absurdities. TODO nix Django ORM.
        #
        # TL;DR we're double-deleting minio data, to be extra-safe. The user
        # said "delete." We'll delete.
        if self.id:  # be extra-safe: use if-statement so we don't remove '/'
            minio.remove_recursive(minio.StoredObjectsBucket, f"{self.id}/")
            minio.remove_recursive(minio.UserFilesBucket, f"wf-{self.id}/")

        super().delete(*args, **kwargs) 

def test_duplicate_order_field(self):
        class Bar(models.Model):
            class Meta:
                app_label = 'order_with_respect_to'

        class Foo(models.Model):
            bar = models.ForeignKey(Bar, models.CASCADE)
            order = models.OrderWrt()

            class Meta:
                order_with_respect_to = 'bar'
                app_label = 'order_with_respect_to'

        count = 0
        for field in Foo._meta.local_fields:
            if isinstance(field, models.OrderWrt):
                count += 1

        self.assertEqual(count, 1) 

def test_name(self):
        """
        Tests the outputting of the correct name if assigned one.
        """
        # First try using a "normal" field
        field = models.CharField(max_length=65)
        name, path, args, kwargs = field.deconstruct()
        self.assertIsNone(name)
        field.set_attributes_from_name("is_awesome_test")
        name, path, args, kwargs = field.deconstruct()
        self.assertEqual(name, "is_awesome_test")
        self.assertIsInstance(name, six.text_type)
        # Now try with a ForeignKey
        field = models.ForeignKey("some_fake.ModelName", models.CASCADE)
        name, path, args, kwargs = field.deconstruct()
        self.assertIsNone(name)
        field.set_attributes_from_name("author")
        name, path, args, kwargs = field.deconstruct()
        self.assertEqual(name, "author") 

def test_sealed_prefetch_related_non_sealable_model(self):
        class NonSealableClimate(models.Model):
            objects = SealableQuerySet.as_manager()

            class Meta:
                db_table = Climate._meta.db_table

        class NonSealableLocationClimatesThrough(models.Model):
            climate = models.ForeignKey(NonSealableClimate, models.CASCADE)
            location = models.ForeignKey('NonSealableLocation', models.CASCADE)

            class Meta:
                db_table = Location.climates.through._meta.db_table

        class NonSealableLocation(models.Model):
            climates = models.ManyToManyField(NonSealableClimate, through=NonSealableLocationClimatesThrough)

            class Meta:
                db_table = Location._meta.db_table
        queryset = SealableQuerySet(model=NonSealableLocation)
        instance = queryset.prefetch_related('climates').seal().get()
        self.assertTrue(instance._state.sealed)
        with self.assertNumQueries(0):
            self.assertTrue(instance.climates.all()[0]._state.sealed) 

def setUpClass(cls):
        """Creates the test model in the database."""

        super(LocalizedExpressionsTestCase, cls).setUpClass()

        cls.TestModel1 = get_fake_model(
            {"name": models.CharField(null=False, blank=False, max_length=255)}
        )

        cls.TestModel2 = get_fake_model(
            {
                "text": LocalizedField(),
                "other": models.ForeignKey(
                    cls.TestModel1,
                    related_name="features",
                    on_delete=models.CASCADE,
                ),
            }
        ) 

def test_parental_key_checks_related_name_is_not_plus(self):
        from django.core import checks
        from django.db import models
        from modelcluster.fields import ParentalKey

        class Instrument(models.Model):
            # Oops, related_name='+' is not allowed
            band = ParentalKey(Band, related_name='+', on_delete=models.CASCADE)

            class Meta:
                # Prevent Django from thinking this is in the database
                # This shouldn't affect the test
                abstract = True

        # Check for error
        errors = Instrument.check()
        self.assertEqual(1, len(errors))

        # Check the error itself
        error = errors[0]
        self.assertIsInstance(error, checks.Error)
        self.assertEqual(error.id, 'modelcluster.E002')
        self.assertEqual(error.obj, Instrument.band.field)
        self.assertEqual(error.msg, "related_name='+' is not allowed on ParentalKey fields")
        self.assertEqual(error.hint, "Either change it to a valid name or remove it") 

def test_foreign_key_to_missing_model(self):
        # Model names are resolved when a model is being created, so we cannot
        # test relative fields in isolation and we need to attach them to a
        # model.
        class Model(models.Model):
            foreign_key = models.ForeignKey('Rel1', models.CASCADE)

        field = Model._meta.get_field('foreign_key')
        self.assertEqual(field.check(), [
            Error(
                "Field defines a relation with model 'Rel1', "
                "which is either not installed, or is abstract.",
                obj=field,
                id='fields.E300',
            ),
        ]) 

def __init__(self, from_fields, to_fields, swappable=True, **kwargs):
        self.from_fields = from_fields
        self.to_fields = to_fields = to_fields
        self.swappable = swappable

        if 'rel' not in kwargs:
            kwargs['rel'] = LayoutForeignObjectRel(
                self, related_name=kwargs.pop('related_name', None),
                related_query_name=kwargs.pop('related_query_name', None),
                limit_choices_to=kwargs.pop('limit_choices_to', None),
                parent_link=kwargs.pop('parent_link', False),
                on_delete=kwargs.pop('on_delete', CASCADE),
            )
        kwargs['verbose_name'] = kwargs.get('verbose_name', None)

        # We want to skip ForeignObject in the MRO, so we can't use super here
        LayoutRelatedField.__init__(self, **kwargs) 

def test_parental_key_checks_target_is_resolved_as_class(self):
        from django.core import checks
        from django.db import models
        from modelcluster.fields import ParentalKey

        class Instrument(models.Model):
            banana = ParentalKey('Banana', on_delete=models.CASCADE)

            class Meta:
                # Prevent Django from thinking this is in the database
                # This shouldn't affect the test
                abstract = True

        # Check for error
        errors = Instrument.check()
        self.assertEqual(1, len(errors))

        # Check the error itself
        error = errors[0]
        self.assertIsInstance(error, checks.Error)
        self.assertEqual(error.id, 'fields.E300')
        self.assertEqual(error.obj, Instrument.banana.field)
        self.assertEqual(error.msg, "Field defines a relation with model 'Banana', which is either not installed, or is abstract.") 

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_sealed_select_related_non_sealable_model(self):
        class NonSealableLocation(models.Model):
            class Meta:
                db_table = Location._meta.db_table

        class NonSealableSeaLion(models.Model):
            location = models.ForeignKey(NonSealableLocation, models.CASCADE)

            class Meta:
                db_table = SeaLion._meta.db_table
        queryset = SealableQuerySet(model=NonSealableSeaLion)
        instance = queryset.select_related('location').seal().get()
        self.assertTrue(instance._state.sealed)
        self.assertTrue(instance.location._state.sealed) 

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(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_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_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_foreign_key_swapped(self):
        with isolate_lru_cache(apps.get_swappable_settings_name):
            # It doesn't matter that we swapped out user for permission;
            # there's no validation. We just want to check the setting stuff works.
            field = models.ForeignKey("auth.Permission", models.CASCADE)
            name, path, args, kwargs = field.deconstruct()

        self.assertEqual(path, "django.db.models.ForeignKey")
        self.assertEqual(args, [])
        self.assertEqual(kwargs, {"to": "auth.Permission", "on_delete": models.CASCADE})
        self.assertEqual(kwargs['to'].setting_name, "AUTH_USER_MODEL") 

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_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_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(
            [name for name, field in project_state.models["migrations", "book"].fields],
            ["id", "author"],
        ) 

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_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_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_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) 

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])