text: import unittest
  
  from django.conf import settings
  from django.core.checks import Error, Warning
  from django.core.checks.model_checks import _check_lazy_references
  from django.core.exceptions import ImproperlyConfigured
  from django.db import connection, connections, models
  from django.db.models.signals import post_init
  from django.test import SimpleTestCase
  from django.test.utils import isolate_apps, override_settings
  
  
  def get_max_column_name_length():
      allowed_len = None
      db_alias = None
  
      for db in settings.DATABASES:
          connection = connections[db]
          max_name_length = connection.ops.max_name_length()
          if max_name_length is not None and not connection.features.truncates_names:
              if allowed_len is None or max_name_length < allowed_len:
                  allowed_len = max_name_length
                  db_alias = db
  
      return (allowed_len, db_alias)
  
  
  @isolate_apps('invalid_models_tests')
  class IndexTogetherTests(SimpleTestCase):
  
      def test_non_iterable(self):
          class Model(models.Model):
              class Meta:
                  index_together = 42
  
          self.assertEqual(Model.check(), [
              Error(
                  "'index_together' must be a list or tuple.",
                  obj=Model,
                  id='models.E008',
              ),
          ])
  
      def test_non_list(self):
          class Model(models.Model):
              class Meta:
                  index_together = 'not-a-list'
  
          self.assertEqual(Model.check(), [
              Error(
                  "'index_together' must be a list or tuple.",
                  obj=Model,
                  id='models.E008',
              ),
          ])
  
      def test_list_containing_non_iterable(self):
          class Model(models.Model):
              class Meta:
                  index_together = [('a', 'b'), 42]
  
          self.assertEqual(Model.check(), [
              Error(
                  "All 'index_together' elements must be lists or tuples.",
                  obj=Model,
                  id='models.E009',
              ),
          ])
  
      def test_pointing_to_missing_field(self):
          class Model(models.Model):
              class Meta:
                  index_together = [['missing_field']]
  
          self.assertEqual(Model.check(), [
              Error(
                  "'index_together' refers to the nonexistent field 'missing_field'.",
                  obj=Model,
                  id='models.E012',
              ),
          ])
  
      def test_pointing_to_non_local_field(self):
          class Foo(models.Model):
              field1 = models.IntegerField()
  
          class Bar(Foo):
              field2 = models.IntegerField()
  
              class Meta:
                  index_together = [['field2', 'field1']]
  
          self.assertEqual(Bar.check(), [
              Error(
                  "'index_together' refers to field 'field1' which is not "
                  "local to model 'Bar'.",
                  hint='This issue may be caused by multi-table inheritance.',
                  obj=Bar,
                  id='models.E016',
              ),
          ])
  
      def test_pointing_to_m2m_field(self):
          class Model(models.Model):
              m2m = models.ManyToManyField('self')
  
              class Meta:
                  index_together = [['m2m']]
  
          self.assertEqual(Model.check(), [
              Error(
                  "'index_together' refers to a ManyToManyField 'm2m', but "
                  "ManyToManyFields are not permitted in 'index_together'.",
                  obj=Model,
                  id='models.E013',
              ),
          ])
  
  
  # unique_together tests are very similar to index_together tests.
  @isolate_apps('invalid_models_tests')
  class UniqueTogetherTests(SimpleTestCase):
  
      def test_non_iterable(self):
          class Model(models.Model):
              class Meta:
                  unique_together = 42
  
          self.assertEqual(Model.check(), [
              Error(
                  "'unique_together' must be a list or tuple.",
                  obj=Model,
                  id='models.E010',
              ),
          ])
  
      def test_list_containing_non_iterable(self):
          class Model(models.Model):
              one = models.IntegerField()
              two = models.IntegerField()
  
              class Meta:
                  unique_together = [('a', 'b'), 42]
  
          self.assertEqual(Model.check(), [
              Error(
                  "All 'unique_together' elements must be lists or tuples.",
                  obj=Model,
                  id='models.E011',
              ),
          ])
  
      def test_non_list(self):
          class Model(models.Model):
              class Meta:
                  unique_together = 'not-a-list'
  
          self.assertEqual(Model.check(), [
              Error(
                  "'unique_together' must be a list or tuple.",
                  obj=Model,
                  id='models.E010',
              ),
          ])
  
      def test_valid_model(self):
          class Model(models.Model):
              one = models.IntegerField()
              two = models.IntegerField()
  
              class Meta:
                  # unique_together can be a simple tuple
                  unique_together = ('one', 'two')
  
          self.assertEqual(Model.check(), [])
  
      def test_pointing_to_missing_field(self):
          class Model(models.Model):
              class Meta:
                  unique_together = [['missing_field']]
  
          self.assertEqual(Model.check(), [
              Error(
                  "'unique_together' refers to the nonexistent field 'missing_field'.",
                  obj=Model,
                  id='models.E012',
              ),
          ])
  
      def test_pointing_to_m2m(self):
          class Model(models.Model):
              m2m = models.ManyToManyField('self')
  
              class Meta:
                  unique_together = [['m2m']]
  
          self.assertEqual(Model.check(), [
              Error(
                  "'unique_together' refers to a ManyToManyField 'm2m', but "
                  "ManyToManyFields are not permitted in 'unique_together'.",
                  obj=Model,
                  id='models.E013',
              ),
          ])
  
  
  @isolate_apps('invalid_models_tests')
  class IndexesTests(SimpleTestCase):
  
      def test_pointing_to_missing_field(self):
          class Model(models.Model):
              class Meta:
                  indexes = [models.Index(fields=['missing_field'], name='name')]
  
          self.assertEqual(Model.check(), [
              Error(
                  "'indexes' refers to the nonexistent field 'missing_field'.",
                  obj=Model,
                  id='models.E012',
              ),
          ])
  
      def test_pointing_to_m2m_field(self):
          class Model(models.Model):
              m2m = models.ManyToManyField('self')
  
              class Meta:
                  indexes = [models.Index(fields=['m2m'], name='name')]
  
          self.assertEqual(Model.check(), [
              Error(
                  "'indexes' refers to a ManyToManyField 'm2m', but "
                  "ManyToManyFields are not permitted in 'indexes'.",
                  obj=Model,
                  id='models.E013',
              ),
          ])
  
      def test_pointing_to_non_local_field(self):
          class Foo(models.Model):
              field1 = models.IntegerField()
  
          class Bar(Foo):
              field2 = models.IntegerField()
  
              class Meta:
                  indexes = [models.Index(fields=['field2', 'field1'], name='name')]
  
          self.assertEqual(Bar.check(), [
              Error(
                  "'indexes' refers to field 'field1' which is not local to "
                  "model 'Bar'.",
                  hint='This issue may be caused by multi-table inheritance.',
                  obj=Bar,
                  id='models.E016',
              ),
          ])
  
  
  @isolate_apps('invalid_models_tests')
  class FieldNamesTests(SimpleTestCase):
  
      def test_ending_with_underscore(self):
          class Model(models.Model):
              field_ = models.CharField(max_length=10)
              m2m_ = models.ManyToManyField('self')
  
          self.assertEqual(Model.check(), [
              Error(
                  'Field names must not end with an underscore.',
                  obj=Model._meta.get_field('field_'),
                  id='fields.E001',
              ),
              Error(
                  'Field names must not end with an underscore.',
                  obj=Model._meta.get_field('m2m_'),
                  id='fields.E001',
              ),
          ])
  
      max_column_name_length, column_limit_db_alias = get_max_column_name_length()
  
      @unittest.skipIf(max_column_name_length is None, "The database doesn't have a column name length limit.")
      def test_M2M_long_column_name(self):
          """
          #13711 -- Model check for long M2M column names when database has
          column name length limits.
          """
          allowed_len, db_alias = get_max_column_name_length()
  
          # A model with very long name which will be used to set relations to.
          class VeryLongModelNamezzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzz(models.Model):
              title = models.CharField(max_length=11)
  
          # Main model for which checks will be performed.
          class ModelWithLongField(models.Model):
              m2m_field = models.ManyToManyField(
                  VeryLongModelNamezzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzz,
                  related_name='rn1',
              )
              m2m_field2 = models.ManyToManyField(
                  VeryLongModelNamezzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzz,
                  related_name='rn2', through='m2msimple',
              )
              m2m_field3 = models.ManyToManyField(
                  VeryLongModelNamezzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzz,
                  related_name='rn3',
                  through='m2mcomplex',
              )
              fk = models.ForeignKey(
                  VeryLongModelNamezzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzz,
                  models.CASCADE,
                  related_name='rn4',
              )
  
          # Models used for setting `through` in M2M field.
          class m2msimple(models.Model):
              id2 = models.ForeignKey(ModelWithLongField, models.CASCADE)
  
          class m2mcomplex(models.Model):
              id2 = models.ForeignKey(ModelWithLongField, models.CASCADE)
  
          long_field_name = 'a' * (self.max_column_name_length + 1)
          models.ForeignKey(
              VeryLongModelNamezzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzz,
              models.CASCADE,
          ).contribute_to_class(m2msimple, long_field_name)
  
          models.ForeignKey(
              VeryLongModelNamezzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzz,
              models.CASCADE,
              db_column=long_field_name
          ).contribute_to_class(m2mcomplex, long_field_name)
  
          errors = ModelWithLongField.check()
  
          # First error because of M2M field set on the model with long name.
          m2m_long_name = "verylongmodelnamezzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzz_id"
          if self.max_column_name_length > len(m2m_long_name):
              # Some databases support names longer than the test name.
              expected = []
          else:
              expected = [
                  Error(
                      'Autogenerated column name too long for M2M field "%s". '
                      'Maximum length is "%s" for database "%s".'
                      % (m2m_long_name, self.max_column_name_length, self.column_limit_db_alias),
                      hint="Use 'through' to create a separate model for "
                           "M2M and then set column_name using 'db_column'.",
                      obj=ModelWithLongField,
                      id='models.E019',
                  )
              ]
  
          # Second error because the FK specified in the `through` model
          # `m2msimple` has auto-generated name longer than allowed.
          # There will be no check errors in the other M2M because it
          # specifies db_column for the FK in `through` model even if the actual
          # name is longer than the limits of the database.
          expected.append(
              Error(
                  'Autogenerated column name too long for M2M field "%s_id". '
                  'Maximum length is "%s" for database "%s".'
                  % (long_field_name, self.max_column_name_length, self.column_limit_db_alias),
                  hint="Use 'through' to create a separate model for "
                       "M2M and then set column_name using 'db_column'.",
                  obj=ModelWithLongField,
                  id='models.E019',
              )
          )
  
          self.assertEqual(errors, expected)
  
      @unittest.skipIf(max_column_name_length is None, "The database doesn't have a column name length limit.")
      def test_local_field_long_column_name(self):
          """
          #13711 -- Model check for long column names
          when database does not support long names.
          """
          allowed_len, db_alias = get_max_column_name_length()
  
          class ModelWithLongField(models.Model):
              title = models.CharField(max_length=11)
  
          long_field_name = 'a' * (self.max_column_name_length + 1)
          long_field_name2 = 'b' * (self.max_column_name_length + 1)
          models.CharField(max_length=11).contribute_to_class(ModelWithLongField, long_field_name)
          models.CharField(max_length=11, db_column='vlmn').contribute_to_class(ModelWithLongField, long_field_name2)
          self.assertEqual(ModelWithLongField.check(), [
              Error(
                  'Autogenerated column name too long for field "%s". '
                  'Maximum length is "%s" for database "%s".'
                  % (long_field_name, self.max_column_name_length, self.column_limit_db_alias),
                  hint="Set the column name manually using 'db_column'.",
                  obj=ModelWithLongField,
                  id='models.E018',
              )
          ])
  
      def test_including_separator(self):
          class Model(models.Model):
              some__field = models.IntegerField()
  
          self.assertEqual(Model.check(), [
              Error(
                  'Field names must not contain "__".',
                  obj=Model._meta.get_field('some__field'),
                  id='fields.E002',
              )
          ])
  
      def test_pk(self):
          class Model(models.Model):
              pk = models.IntegerField()
  
          self.assertEqual(Model.check(), [
              Error(
                  "'pk' is a reserved word that cannot be used as a field name.",
                  obj=Model._meta.get_field('pk'),
                  id='fields.E003',
              )
          ])
  
  
  @isolate_apps('invalid_models_tests')
  class ShadowingFieldsTests(SimpleTestCase):
  
      def test_field_name_clash_with_child_accessor(self):
          class Parent(models.Model):
              pass
  
          class Child(Parent):
              child = models.CharField(max_length=100)
  
          self.assertEqual(Child.check(), [
              Error(
                  "The field 'child' clashes with the field "
                  "'child' from model 'invalid_models_tests.parent'.",
                  obj=Child._meta.get_field('child'),
                  id='models.E006',
              )
          ])
  
      def test_multiinheritance_clash(self):
          class Mother(models.Model):
              clash = models.IntegerField()
  
          class Father(models.Model):
              clash = models.IntegerField()
  
          class Child(Mother, Father):
              # Here we have two clashed: id (automatic field) and clash, because
              # both parents define these fields.
              pass
  
          self.assertEqual(Child.check(), [
              Error(
                  "The field 'id' from parent model "
                  "'invalid_models_tests.mother' clashes with the field 'id' "
                  "from parent model 'invalid_models_tests.father'.",
                  obj=Child,
                  id='models.E005',
              ),
              Error(
                  "The field 'clash' from parent model "
                  "'invalid_models_tests.mother' clashes with the field 'clash' "
                  "from parent model 'invalid_models_tests.father'.",
                  obj=Child,
                  id='models.E005',
              )
          ])
  
      def test_inheritance_clash(self):
          class Parent(models.Model):
              f_id = models.IntegerField()
  
          class Target(models.Model):
              # This field doesn't result in a clash.
              f_id = models.IntegerField()
  
          class Child(Parent):
              # This field clashes with parent "f_id" field.
              f = models.ForeignKey(Target, models.CASCADE)
  
          self.assertEqual(Child.check(), [
              Error(
                  "The field 'f' clashes with the field 'f_id' "
                  "from model 'invalid_models_tests.parent'.",
                  obj=Child._meta.get_field('f'),
                  id='models.E006',
              )
          ])
  
      def test_multigeneration_inheritance(self):
          class GrandParent(models.Model):
              clash = models.IntegerField()
  
          class Parent(GrandParent):
              pass
  
          class Child(Parent):
              pass
  
          class GrandChild(Child):
              clash = models.IntegerField()
  
          self.assertEqual(GrandChild.check(), [
              Error(
                  "The field 'clash' clashes with the field 'clash' "
                  "from model 'invalid_models_tests.grandparent'.",
                  obj=GrandChild._meta.get_field('clash'),
                  id='models.E006',
              )
          ])
  
      def test_id_clash(self):
          class Target(models.Model):
              pass
  
          class Model(models.Model):
              fk = models.ForeignKey(Target, models.CASCADE)
              fk_id = models.IntegerField()
  
          self.assertEqual(Model.check(), [
              Error(
                  "The field 'fk_id' clashes with the field 'fk' from model "
                  "'invalid_models_tests.model'.",
                  obj=Model._meta.get_field('fk_id'),
                  id='models.E006',
              )
          ])
  
  
  @isolate_apps('invalid_models_tests')
  class OtherModelTests(SimpleTestCase):
  
      def test_unique_primary_key(self):
          invalid_id = models.IntegerField(primary_key=False)
  
          class Model(models.Model):
              id = invalid_id
  
          self.assertEqual(Model.check(), [
              Error(
                  "'id' can only be used as a field name if the field also sets "
                  "'primary_key=True'.",
                  obj=Model,
                  id='models.E004',
              ),
          ])
  
      def test_ordering_non_iterable(self):
          class Model(models.Model):
              class Meta:
                  ordering = 'missing_field'
  
          self.assertEqual(Model.check(), [
              Error(
                  "'ordering' must be a tuple or list "
                  "(even if you want to order by only one field).",
                  obj=Model,
                  id='models.E014',
              ),
          ])
  
      def test_just_ordering_no_errors(self):
          class Model(models.Model):
              order = models.PositiveIntegerField()
  
              class Meta:
                  ordering = ['order']
  
          self.assertEqual(Model.check(), [])
  
      def test_just_order_with_respect_to_no_errors(self):
          class Question(models.Model):
              pass
  
          class Answer(models.Model):
              question = models.ForeignKey(Question, models.CASCADE)
  
              class Meta:
                  order_with_respect_to = 'question'
  
          self.assertEqual(Answer.check(), [])
  
      def test_ordering_with_order_with_respect_to(self):
          class Question(models.Model):
              pass
  
          class Answer(models.Model):
              question = models.ForeignKey(Question, models.CASCADE)
              order = models.IntegerField()
  
              class Meta:
                  order_with_respect_to = 'question'
                  ordering = ['order']
  
          self.assertEqual(Answer.check(), [
              Error(
                  "'ordering' and 'order_with_respect_to' cannot be used together.",
                  obj=Answer,
                  id='models.E021',
              ),
          ])
  
      def test_non_valid(self):
          class RelationModel(models.Model):
              pass
  
          class Model(models.Model):
              relation = models.ManyToManyField(RelationModel)
  
              class Meta:
                  ordering = ['relation']
  
          self.assertEqual(Model.check(), [
              Error(
                  "'ordering' refers to the nonexistent field 'relation'.",
                  obj=Model,
                  id='models.E015',
              ),
          ])
  
      def test_ordering_pointing_to_missing_field(self):
          class Model(models.Model):
              class Meta:
                  ordering = ('missing_field',)
  
          self.assertEqual(Model.check(), [
              Error(
                  "'ordering' refers to the nonexistent field 'missing_field'.",
                  obj=Model,
                  id='models.E015',
              )
          ])
  
      def test_ordering_pointing_to_missing_foreignkey_field(self):
          class Model(models.Model):
              missing_fk_field = models.IntegerField()
  
              class Meta:
                  ordering = ('missing_fk_field_id',)
  
          self.assertEqual(Model.check(), [
              Error(
                  "'ordering' refers to the nonexistent field 'missing_fk_field_id'.",
                  obj=Model,
                  id='models.E015',
              )
          ])
  
      def test_ordering_pointing_to_foreignkey_field(self):
          class Parent(models.Model):
              pass
  
          class Child(models.Model):
              parent = models.ForeignKey(Parent, models.CASCADE)
  
              class Meta:
                  ordering = ('parent_id',)
  
          self.assertFalse(Child.check())
  
      def test_name_beginning_with_underscore(self):
          class _Model(models.Model):
              pass
  
          self.assertEqual(_Model.check(), [
              Error(
                  "The model name '_Model' cannot start or end with an underscore "
                  "as it collides with the query lookup syntax.",
                  obj=_Model,
                  id='models.E023',
              )
          ])
  
      def test_name_ending_with_underscore(self):
          class Model_(models.Model):
              pass
  
          self.assertEqual(Model_.check(), [
              Error(
                  "The model name 'Model_' cannot start or end with an underscore "
                  "as it collides with the query lookup syntax.",
                  obj=Model_,
                  id='models.E023',
              )
          ])
  
      def test_name_contains_double_underscores(self):
          class Test__Model(models.Model):
              pass
  
          self.assertEqual(Test__Model.check(), [
              Error(
                  "The model name 'Test__Model' cannot contain double underscores "
                  "as it collides with the query lookup syntax.",
                  obj=Test__Model,
                  id='models.E024',
              )
          ])
  
      def test_property_and_related_field_accessor_clash(self):
          class Model(models.Model):
              fk = models.ForeignKey('self', models.CASCADE)
  
              @property
              def fk_id(self):
                  pass
  
          self.assertEqual(Model.check(), [
              Error(
                  "The property 'fk_id' clashes with a related field accessor.",
                  obj=Model,
                  id='models.E025',
              )
          ])
  
      def test_single_primary_key(self):
          class Model(models.Model):
              foo = models.IntegerField(primary_key=True)
              bar = models.IntegerField(primary_key=True)
  
          self.assertEqual(Model.check(), [
              Error(
                  "The model cannot have more than one field with 'primary_key=True'.",
                  obj=Model,
                  id='models.E026',
              )
          ])
  
      @override_settings(TEST_SWAPPED_MODEL_BAD_VALUE='not-a-model')
      def test_swappable_missing_app_name(self):
          class Model(models.Model):
              class Meta:
                  swappable = 'TEST_SWAPPED_MODEL_BAD_VALUE'
  
          self.assertEqual(Model.check(), [
              Error(
                  "'TEST_SWAPPED_MODEL_BAD_VALUE' is not of the form 'app_label.app_name'.",
                  id='models.E001',
              ),
          ])
  
      @override_settings(TEST_SWAPPED_MODEL_BAD_MODEL='not_an_app.Target')
      def test_swappable_missing_app(self):
          class Model(models.Model):
              class Meta:
                  swappable = 'TEST_SWAPPED_MODEL_BAD_MODEL'
  
          self.assertEqual(Model.check(), [
              Error(
                  "'TEST_SWAPPED_MODEL_BAD_MODEL' references 'not_an_app.Target', "
                  'which has not been installed, or is abstract.',
                  id='models.E002',
              ),
          ])
  
      def test_two_m2m_through_same_relationship(self):
          class Person(models.Model):
              pass
  
          class Group(models.Model):
              primary = models.ManyToManyField(Person, through='Membership', related_name='primary')
              secondary = models.ManyToManyField(Person, through='Membership', related_name='secondary')
  
          class Membership(models.Model):
              person = models.ForeignKey(Person, models.CASCADE)
              group = models.ForeignKey(Group, models.CASCADE)
  
          self.assertEqual(Group.check(), [
              Error(
                  "The model has two identical many-to-many relations through "
                  "the intermediate model 'invalid_models_tests.Membership'.",
                  obj=Group,
                  id='models.E003',
              )
          ])
  
      def test_two_m2m_through_same_model_with_different_through_fields(self):
          class Country(models.Model):
              pass
  
          class ShippingMethod(models.Model):
              to_countries = models.ManyToManyField(
                  Country, through='ShippingMethodPrice',
                  through_fields=('method', 'to_country'),
              )
              from_countries = models.ManyToManyField(
                  Country, through='ShippingMethodPrice',
                  through_fields=('method', 'from_country'),
                  related_name='+',
              )
  
          class ShippingMethodPrice(models.Model):
              method = models.ForeignKey(ShippingMethod, models.CASCADE)
              to_country = models.ForeignKey(Country, models.CASCADE)
              from_country = models.ForeignKey(Country, models.CASCADE)
  
          self.assertEqual(ShippingMethod.check(), [])
  
      def test_missing_parent_link(self):
          msg = 'Add parent_link=True to invalid_models_tests.ParkingLot.parent.'
          with self.assertRaisesMessage(ImproperlyConfigured, msg):
              class Place(models.Model):
                  pass
  
              class ParkingLot(Place):
                  parent = models.OneToOneField(Place, models.CASCADE)
  
      def test_m2m_table_name_clash(self):
          class Foo(models.Model):
              bar = models.ManyToManyField('Bar', db_table='myapp_bar')
  
              class Meta:
                  db_table = 'myapp_foo'
  
          class Bar(models.Model):
              class Meta:
                  db_table = 'myapp_bar'
  
          self.assertEqual(Foo.check(), [
              Error(
                  "The field's intermediary table 'myapp_bar' clashes with the "
                  "table name of 'invalid_models_tests.Bar'.",
                  obj=Foo._meta.get_field('bar'),
                  id='fields.E340',
              )
          ])
  
      def test_m2m_field_table_name_clash(self):
          class Foo(models.Model):
              pass
  
          class Bar(models.Model):
              foos = models.ManyToManyField(Foo, db_table='clash')
  
          class Baz(models.Model):
              foos = models.ManyToManyField(Foo, db_table='clash')
  
          self.assertEqual(Bar.check() + Baz.check(), [
              Error(
                  "The field's intermediary table 'clash' clashes with the "
                  "table name of 'invalid_models_tests.Baz.foos'.",
                  obj=Bar._meta.get_field('foos'),
                  id='fields.E340',
              ),
              Error(
                  "The field's intermediary table 'clash' clashes with the "
                  "table name of 'invalid_models_tests.Bar.foos'.",
                  obj=Baz._meta.get_field('foos'),
                  id='fields.E340',
              )
          ])
  
      def test_m2m_autogenerated_table_name_clash(self):
          class Foo(models.Model):
              class Meta:
                  db_table = 'bar_foos'
  
          class Bar(models.Model):
              # The autogenerated `db_table` will be bar_foos.
              foos = models.ManyToManyField(Foo)
  
              class Meta:
                  db_table = 'bar'
  
          self.assertEqual(Bar.check(), [
              Error(
                  "The field's intermediary table 'bar_foos' clashes with the "
                  "table name of 'invalid_models_tests.Foo'.",
                  obj=Bar._meta.get_field('foos'),
                  id='fields.E340',
              )
          ])
  
      def test_m2m_unmanaged_shadow_models_not_checked(self):
          class A1(models.Model):
              pass
  
          class C1(models.Model):
              mm_a = models.ManyToManyField(A1, db_table='d1')
  
          # Unmanaged models that shadow the above models. Reused table names
          # shouldn't be flagged by any checks.
          class A2(models.Model):
              class Meta:
                  managed = False
  
          class C2(models.Model):
              mm_a = models.ManyToManyField(A2, through='Intermediate')
  
              class Meta:
                  managed = False
  
          class Intermediate(models.Model):
              a2 = models.ForeignKey(A2, models.CASCADE, db_column='a1_id')
              c2 = models.ForeignKey(C2, models.CASCADE, db_column='c1_id')
  
              class Meta:
                  db_table = 'd1'
                  managed = False
  
          self.assertEqual(C1.check(), [])
          self.assertEqual(C2.check(), [])
  
      def test_m2m_to_concrete_and_proxy_allowed(self):
          class A(models.Model):
              pass
  
          class Through(models.Model):
              a = models.ForeignKey('A', models.CASCADE)
              c = models.ForeignKey('C', models.CASCADE)
  
          class ThroughProxy(Through):
              class Meta:
                  proxy = True
  
          class C(models.Model):
              mm_a = models.ManyToManyField(A, through=Through)
              mm_aproxy = models.ManyToManyField(A, through=ThroughProxy, related_name='proxied_m2m')
  
          self.assertEqual(C.check(), [])
  
      @isolate_apps('django.contrib.auth', kwarg_name='apps')
      def test_lazy_reference_checks(self, apps):
          class DummyModel(models.Model):
              author = models.ForeignKey('Author', models.CASCADE)
  
              class Meta:
                  app_label = 'invalid_models_tests'
  
          class DummyClass:
              def __call__(self, **kwargs):
                  pass
  
              def dummy_method(self):
                  pass
  
          def dummy_function(*args, **kwargs):
              pass
  
          apps.lazy_model_operation(dummy_function, ('auth', 'imaginarymodel'))
          apps.lazy_model_operation(dummy_function, ('fanciful_app', 'imaginarymodel'))
  
          post_init.connect(dummy_function, sender='missing-app.Model', apps=apps)
          post_init.connect(DummyClass(), sender='missing-app.Model', apps=apps)
          post_init.connect(DummyClass().dummy_method, sender='missing-app.Model', apps=apps)
  
          self.assertEqual(_check_lazy_references(apps), [
              Error(
                  "%r contains a lazy reference to auth.imaginarymodel, "
                  "but app 'auth' doesn't provide model 'imaginarymodel'." % dummy_function,
                  obj=dummy_function,
                  id='models.E022',
              ),
              Error(
                  "%r contains a lazy reference to fanciful_app.imaginarymodel, "
                  "but app 'fanciful_app' isn't installed." % dummy_function,
                  obj=dummy_function,
                  id='models.E022',
              ),
              Error(
                  "An instance of class 'DummyClass' was connected to "
                  "the 'post_init' signal with a lazy reference to the sender "
                  "'missing-app.model', but app 'missing-app' isn't installed.",
                  hint=None,
                  obj='invalid_models_tests.test_models',
                  id='signals.E001',
              ),
              Error(
                  "Bound method 'DummyClass.dummy_method' was connected to the "
                  "'post_init' signal with a lazy reference to the sender "
                  "'missing-app.model', but app 'missing-app' isn't installed.",
                  hint=None,
                  obj='invalid_models_tests.test_models',
                  id='signals.E001',
              ),
              Error(
                  "The field invalid_models_tests.DummyModel.author was declared "
                  "with a lazy reference to 'invalid_models_tests.author', but app "
                  "'invalid_models_tests' isn't installed.",
                  hint=None,
                  obj=DummyModel.author.field,
                  id='fields.E307',
              ),
              Error(
                  "The function 'dummy_function' was connected to the 'post_init' "
                  "signal with a lazy reference to the sender "
                  "'missing-app.model', but app 'missing-app' isn't installed.",
                  hint=None,
                  obj='invalid_models_tests.test_models',
                  id='signals.E001',
              ),
          ])
  
  
  @isolate_apps('invalid_models_tests')
  class ConstraintsTests(SimpleTestCase):
      def test_check_constraints(self):
          class Model(models.Model):
              age = models.IntegerField()
  
              class Meta:
                  constraints = [models.CheckConstraint(check=models.Q(age__gte=18), name='is_adult')]
  
          errors = Model.check()
          warn = Warning(
              '%s does not support check constraints.' % connection.display_name,
              hint=(
                  "A constraint won't be created. Silence this warning if you "
                  "don't care about it."
              ),
              obj=Model,
              id='models.W027',
          )
          expected = [] if connection.features.supports_table_check_constraints else [warn, warn]
          self.assertCountEqual(errors, expected)
  