single layer multiple inheritance is as expected deriving the inherited field from the first base in contrast to standard python mro resolution of inherited fields is strictly depthfirst rather than breadthfirst in diamondshaped cases this is because a copy of the parent field descriptor is placed onto the model class in modelbase new rather than the attribute lookup going via bases it only looks like inheritance here child inherits name from root rather than parentb where the child model needs to inherit a field from a different base than that given by depthfirst resolution the target field can be pushed down by being redeclared single layer multiple inheritance is as expected deriving the inherited field from the first base in contrast to standard python mro resolution of inherited fields is strictly depth first rather than breadth first in diamond shaped cases this is because a copy of the parent field descriptor is placed onto the model class in modelbase __new__ rather than the attribute lookup going via bases it only looks like inheritance here child inherits name from root rather than parentb where the child model needs to inherit a field from a different base than that given by depth first resolution the target field can be pushed down by being re declared
from django.contrib.contenttypes.fields import GenericForeignKey, GenericRelation
from django.contrib.contenttypes.models import ContentType
from django.core.checks import Error
from django.core.exceptions import FieldDoesNotExist, FieldError
from django.db import models
from django.test import SimpleTestCase
from django.test.utils import isolate_apps


@isolate_apps("model_inheritance")
class AbstractInheritanceTests(SimpleTestCase):
    def test_single_parent(self):
        class AbstractBase(models.Model):
            name = models.CharField(max_length=30)

            class Meta:
                abstract = True

        class AbstractDescendant(AbstractBase):
            name = models.CharField(max_length=50)

            class Meta:
                abstract = True

        class DerivedChild(AbstractBase):
            name = models.CharField(max_length=50)

        class DerivedGrandChild(AbstractDescendant):
            pass

        self.assertEqual(AbstractDescendant._meta.get_field("name").max_length, 50)
        self.assertEqual(DerivedChild._meta.get_field("name").max_length, 50)
        self.assertEqual(DerivedGrandChild._meta.get_field("name").max_length, 50)

    def test_multiple_inheritance_allows_inherited_field(self):
        

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

            class Meta:
                abstract = True

        class ParentB(models.Model):
            name = models.IntegerField()

            class Meta:
                abstract = True

        class Child(ParentA, ParentB):
            pass

        self.assertEqual(Child.check(), [])
        inherited_field = Child._meta.get_field("name")
        self.assertIsInstance(inherited_field, models.CharField)
        self.assertEqual(inherited_field.max_length, 255)

    def test_diamond_shaped_multiple_inheritance_is_depth_first(self):
        

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

            class Meta:
                abstract = True

        class ParentA(Root):
            class Meta:
                abstract = True

        class ParentB(Root):
            name = models.IntegerField()

            class Meta:
                abstract = True

        class Child(ParentA, ParentB):
            pass

        self.assertEqual(Child.check(), [])
        inherited_field = Child._meta.get_field("name")
        self.assertIsInstance(inherited_field, models.CharField)
        self.assertEqual(inherited_field.max_length, 255)

    def test_target_field_may_be_pushed_down(self):
        

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

            class Meta:
                abstract = True

        class ParentA(Root):
            class Meta:
                abstract = True

        class ParentB(Root):
            name = models.IntegerField()

            class Meta:
                abstract = True

        class Child(ParentA, ParentB):
            name = models.IntegerField()

        self.assertEqual(Child.check(), [])
        inherited_field = Child._meta.get_field("name")
        self.assertIsInstance(inherited_field, models.IntegerField)

    def test_multiple_inheritance_cannot_shadow_concrete_inherited_field(self):
        class ConcreteParent(models.Model):
            name = models.CharField(max_length=255)

        class AbstractParent(models.Model):
            name = models.IntegerField()

            class Meta:
                abstract = True

        class FirstChild(ConcreteParent, AbstractParent):
            pass

        class AnotherChild(AbstractParent, ConcreteParent):
            pass

        self.assertIsInstance(FirstChild._meta.get_field("name"), models.CharField)
        self.assertEqual(
            AnotherChild.check(),
            [
                Error(
                    "The field 'name' clashes with the field 'name' "
                    "from model 'model_inheritance.concreteparent'.",
                    obj=AnotherChild._meta.get_field("name"),
                    id="models.E006",
                )
            ],
        )

    def test_virtual_field(self):
        class RelationModel(models.Model):
            content_type = models.ForeignKey(ContentType, models.CASCADE)
            object_id = models.PositiveIntegerField()
            content_object = GenericForeignKey("content_type", "object_id")

        class RelatedModelAbstract(models.Model):
            field = GenericRelation(RelationModel)

            class Meta:
                abstract = True

        class ModelAbstract(models.Model):
            field = models.CharField(max_length=100)

            class Meta:
                abstract = True

        class OverrideRelatedModelAbstract(RelatedModelAbstract):
            field = models.CharField(max_length=100)

        class ExtendModelAbstract(ModelAbstract):
            field = GenericRelation(RelationModel)

        self.assertIsInstance(
            OverrideRelatedModelAbstract._meta.get_field("field"), models.CharField
        )
        self.assertIsInstance(
            ExtendModelAbstract._meta.get_field("field"), GenericRelation
        )

    def test_cannot_override_indirect_abstract_field(self):
        class AbstractBase(models.Model):
            name = models.CharField(max_length=30)

            class Meta:
                abstract = True

        class ConcreteDescendant(AbstractBase):
            pass

        msg = (
            "Local field 'name' in class 'Descendant' clashes with field of "
            "the same name from base class 'ConcreteDescendant'."
        )
        with self.assertRaisesMessage(FieldError, msg):

            class Descendant(ConcreteDescendant):
                name = models.IntegerField()

    def test_override_field_with_attr(self):
        class AbstractBase(models.Model):
            first_name = models.CharField(max_length=50)
            last_name = models.CharField(max_length=50)
            middle_name = models.CharField(max_length=30)
            full_name = models.CharField(max_length=150)

            class Meta:
                abstract = True

        class Descendant(AbstractBase):
            middle_name = None

            def full_name(self):
                return self.first_name + self.last_name

        msg = "Descendant has no field named %r"
        with self.assertRaisesMessage(FieldDoesNotExist, msg % "middle_name"):
            Descendant._meta.get_field("middle_name")

        with self.assertRaisesMessage(FieldDoesNotExist, msg % "full_name"):
            Descendant._meta.get_field("full_name")

    def test_overriding_field_removed_by_concrete_model(self):
        class AbstractModel(models.Model):
            foo = models.CharField(max_length=30)

            class Meta:
                abstract = True

        class RemovedAbstractModelField(AbstractModel):
            foo = None

        class OverrideRemovedFieldByConcreteModel(RemovedAbstractModelField):
            foo = models.CharField(max_length=50)

        self.assertEqual(
            OverrideRemovedFieldByConcreteModel._meta.get_field("foo").max_length, 50
        )

    def test_shadowed_fkey_id(self):
        class Foo(models.Model):
            pass

        class AbstractBase(models.Model):
            foo = models.ForeignKey(Foo, models.CASCADE)

            class Meta:
                abstract = True

        class Descendant(AbstractBase):
            foo_id = models.IntegerField()

        self.assertEqual(
            Descendant.check(),
            [
                Error(
                    "The field 'foo_id' clashes with the field 'foo' "
                    "from model 'model_inheritance.descendant'.",
                    obj=Descendant._meta.get_field("foo_id"),
                    id="models.E006",
                )
            ],
        )

    def test_shadow_related_name_when_set_to_none(self):
        class AbstractBase(models.Model):
            bar = models.IntegerField()

            class Meta:
                abstract = True

        class Foo(AbstractBase):
            bar = None
            foo = models.IntegerField()

        class Bar(models.Model):
            bar = models.ForeignKey(Foo, models.CASCADE, related_name="bar")

        self.assertEqual(Bar.check(), [])

    def test_reverse_foreign_key(self):
        class AbstractBase(models.Model):
            foo = models.CharField(max_length=100)

            class Meta:
                abstract = True

        class Descendant(AbstractBase):
            pass

        class Foo(models.Model):
            foo = models.ForeignKey(Descendant, models.CASCADE, related_name="foo")

        self.assertEqual(
            Foo._meta.get_field("foo").check(),
            [
                Error(
                    "Reverse accessor 'Descendant.foo' for "
                    "'model_inheritance.Foo.foo' clashes with field name "
                    "'model_inheritance.Descendant.foo'.",
                    hint=(
                        "Rename field 'model_inheritance.Descendant.foo', or "
                        "add/change a related_name argument to the definition "
                        "for field 'model_inheritance.Foo.foo'."
                    ),
                    obj=Foo._meta.get_field("foo"),
                    id="fields.E302",
                ),
                Error(
                    "Reverse query name for 'model_inheritance.Foo.foo' "
                    "clashes with field name "
                    "'model_inheritance.Descendant.foo'.",
                    hint=(
                        "Rename field 'model_inheritance.Descendant.foo', or "
                        "add/change a related_name argument to the definition "
                        "for field 'model_inheritance.Foo.foo'."
                    ),
                    obj=Foo._meta.get_field("foo"),
                    id="fields.E303",
                ),
            ],
        )

    def test_multi_inheritance_field_clashes(self):
        class AbstractBase(models.Model):
            name = models.CharField(max_length=30)

            class Meta:
                abstract = True

        class ConcreteBase(AbstractBase):
            pass

        class AbstractDescendant(ConcreteBase):
            class Meta:
                abstract = True

        class ConcreteDescendant(AbstractDescendant):
            name = models.CharField(max_length=100)

        self.assertEqual(
            ConcreteDescendant.check(),
            [
                Error(
                    "The field 'name' clashes with the field 'name' from "
                    "model 'model_inheritance.concretebase'.",
                    obj=ConcreteDescendant._meta.get_field("name"),
                    id="models.E006",
                )
            ],
        )

    def test_override_one2one_relation_auto_field_clashes(self):
        class ConcreteParent(models.Model):
            name = models.CharField(max_length=255)

        class AbstractParent(models.Model):
            name = models.IntegerField()

            class Meta:
                abstract = True

        msg = (
            "Auto-generated field 'concreteparent_ptr' in class 'Descendant' "
            "for parent_link to base class 'ConcreteParent' clashes with "
            "declared field of the same name."
        )
        with self.assertRaisesMessage(FieldError, msg):

            class Descendant(ConcreteParent, AbstractParent):
                concreteparent_ptr = models.CharField(max_length=30)

    def test_abstract_model_with_regular_python_mixin_mro(self):
        class AbstractModel(models.Model):
            name = models.CharField(max_length=255)
            age = models.IntegerField()

            class Meta:
                abstract = True

        class Mixin:
            age = None

        class Mixin2:
            age = 2

        class DescendantMixin(Mixin):
            pass

        class ConcreteModel(models.Model):
            foo = models.IntegerField()

        class ConcreteModel2(ConcreteModel):
            age = models.SmallIntegerField()

        def fields(model):
            if not hasattr(model, "_meta"):
                return []
            return [(f.name, f.__class__) for f in model._meta.get_fields()]

        model_dict = {"__module__": "model_inheritance"}
        model1 = type("Model1", (AbstractModel, Mixin), model_dict.copy())
        model2 = type("Model2", (Mixin2, AbstractModel), model_dict.copy())
        model3 = type("Model3", (DescendantMixin, AbstractModel), model_dict.copy())
        model4 = type("Model4", (Mixin2, Mixin, AbstractModel), model_dict.copy())
        model5 = type(
            "Model5", (Mixin2, ConcreteModel2, Mixin, AbstractModel), model_dict.copy()
        )

        self.assertEqual(
            fields(model1),
            [
                ("id", models.AutoField),
                ("name", models.CharField),
                ("age", models.IntegerField),
            ],
        )

        self.assertEqual(
            fields(model2), [("id", models.AutoField), ("name", models.CharField)]
        )
        self.assertEqual(getattr(model2, "age"), 2)

        self.assertEqual(
            fields(model3), [("id", models.AutoField), ("name", models.CharField)]
        )

        self.assertEqual(
            fields(model4), [("id", models.AutoField), ("name", models.CharField)]
        )
        self.assertEqual(getattr(model4, "age"), 2)

        self.assertEqual(
            fields(model5),
            [
                ("id", models.AutoField),
                ("foo", models.IntegerField),
                ("concretemodel_ptr", models.OneToOneField),
                ("age", models.SmallIntegerField),
                ("concretemodel2_ptr", models.OneToOneField),
                ("name", models.CharField),
            ],
        )