Fixed #22750, #22248: Model renaming now also alters field FKs

django/db/migrations/autodetector.py

@@ -580,11 +580,21 @@ def generate_altered_fields(self):
         for app_label, model_name, field_name in sorted(self.old_field_keys.intersection(self.new_field_keys)):
             # Did the field change?
             old_model_name = self.renamed_models.get((app_label, model_name), model_name)
-            old_model_state = self.from_state.models[app_label, old_model_name]
             new_model_state = self.to_state.models[app_label, model_name]
             old_field_name = self.renamed_fields.get((app_label, model_name, field_name), field_name)
-            old_field_dec = self.deep_deconstruct(old_model_state.get_field_by_name(old_field_name))
-            new_field_dec = self.deep_deconstruct(new_model_state.get_field_by_name(field_name))
+            old_field = self.old_apps.get_model(app_label, old_model_name)._meta.get_field_by_name(old_field_name)[0]
+            new_field = self.new_apps.get_model(app_label, model_name)._meta.get_field_by_name(field_name)[0]
+            # Implement any model renames on relations; these are handled by RenameModel
+            # so we need to exclude them from the comparison
+            if hasattr(new_field, "rel") and getattr(new_field.rel, "to", None):
+                rename_key = (
+                    new_field.rel.to._meta.app_label,
+                    new_field.rel.to._meta.object_name.lower(),
+                )
+                if rename_key in self.renamed_models:
+                    new_field.rel.to = old_field.rel.to
+            old_field_dec = self.deep_deconstruct(old_field)
+            new_field_dec = self.deep_deconstruct(new_field)
             if old_field_dec != new_field_dec:
                 self.add_operation(
                     app_label,

django/db/migrations/operations/models.py

@@ -113,33 +113,59 @@ def __init__(self, old_name, new_name):
         self.new_name = new_name
 
     def state_forwards(self, app_label, state):
+        # Get all of the related objects we need to repoint
+        apps = state.render(skip_cache=True)
+        model = apps.get_model(app_label, self.old_name)
+        related_objects = model._meta.get_all_related_objects()
+        related_m2m_objects = model._meta.get_all_related_many_to_many_objects()
+        # Rename the model
         state.models[app_label, self.new_name.lower()] = state.models[app_label, self.old_name.lower()]
         state.models[app_label, self.new_name.lower()].name = self.new_name
         del state.models[app_label, self.old_name.lower()]
+        # Repoint the FKs and M2Ms pointing to us
+        for related_object in (related_objects + related_m2m_objects):
+            related_key = (
+                related_object.model._meta.app_label,
+                related_object.model._meta.object_name.lower(),
+            )
+            new_fields = []
+            for name, field in state.models[related_key].fields:
+                if name == related_object.field.name:
+                    field = field.clone()
+                    field.rel.to = "%s.%s" % (app_label, self.new_name)
+                new_fields.append((name, field))
+            state.models[related_key].fields = new_fields
 
     def database_forwards(self, app_label, schema_editor, from_state, to_state):
         old_apps = from_state.render()
         new_apps = to_state.render()
         old_model = old_apps.get_model(app_label, self.old_name)
         new_model = new_apps.get_model(app_label, self.new_name)
         if router.allow_migrate(schema_editor.connection.alias, new_model):
+            # Move the main table
             schema_editor.alter_db_table(
                 new_model,
                 old_model._meta.db_table,
                 new_model._meta.db_table,
             )
+            # Alter the fields pointing to us
+            related_objects = old_model._meta.get_all_related_objects()
+            related_m2m_objects = old_model._meta.get_all_related_many_to_many_objects()
+            for related_object in (related_objects + related_m2m_objects):
+                to_field = new_apps.get_model(
+                    related_object.model._meta.app_label,
+                    related_object.model._meta.object_name.lower(),
+                )._meta.get_field_by_name(related_object.field.name)[0]
+                schema_editor.alter_field(
+                    related_object.model,
+                    related_object.field,
+                    to_field,
+                )
 
     def database_backwards(self, app_label, schema_editor, from_state, to_state):
-        old_apps = from_state.render()
-        new_apps = to_state.render()
-        old_model = old_apps.get_model(app_label, self.new_name)
-        new_model = new_apps.get_model(app_label, self.old_name)
-        if router.allow_migrate(schema_editor.connection.alias, new_model):
-            schema_editor.alter_db_table(
-                new_model,
-                old_model._meta.db_table,
-                new_model._meta.db_table,
-            )
+        self.new_name, self.old_name = self.old_name, self.new_name
+        self.database_forwards(app_label, schema_editor, from_state, to_state)
+        self.new_name, self.old_name = self.old_name, self.new_name
 
     def references_model(self, name, app_label=None):
         return (

django/db/migrations/state.py

@@ -38,9 +38,9 @@ def clone(self):
             real_apps=self.real_apps,
         )
 
-    def render(self, include_real=None, ignore_swappable=False):
+    def render(self, include_real=None, ignore_swappable=False, skip_cache=False):
         "Turns the project state into actual models in a new Apps"
-        if self.apps is None:
+        if self.apps is None or skip_cache:
             # Any apps in self.real_apps should have all their models included
             # in the render. We don't use the original model instances as there
             # are some variables that refer to the Apps object.
@@ -87,7 +87,11 @@ def render(self, include_real=None, ignore_swappable=False):
                         ))
                     else:
                         do_pending_lookups(model)
-        return self.apps
+        try:
+            return self.apps
+        finally:
+            if skip_cache:
+                self.apps = None
 
     @classmethod
     def from_apps(cls, apps):

tests/migrations/test_autodetector.py

@@ -77,9 +77,7 @@ def repr_changes(self, changes):
         return output
 
     def assertNumberMigrations(self, changes, app_label, number):
-        if not changes.get(app_label, None):
-            self.fail("No migrations found for %s\n%s" % (app_label, self.repr_changes(changes)))
-        if len(changes[app_label]) != number:
+        if len(changes.get(app_label, [])) != number:
             self.fail("Incorrect number of migrations (%s) for %s (expected %s)\n%s" % (
                 len(changes[app_label]),
                 app_label,
@@ -285,7 +283,7 @@ def test_rename_model(self):
         changes = autodetector._detect_changes()
 
         # Right number of migrations for model rename?
-        self.assertEqual(len(changes['testapp']), 1)
+        self.assertNumberMigrations(changes, 'testapp', 1)
         # Right number of actions?
         migration = changes['testapp'][0]
         self.assertEqual(len(migration.operations), 1)
@@ -294,17 +292,9 @@ def test_rename_model(self):
         self.assertEqual(action.__class__.__name__, "RenameModel")
         self.assertEqual(action.old_name, "Author")
         self.assertEqual(action.new_name, "Writer")
-
-        # Right number of migrations for related field rename?
-        self.assertEqual(len(changes['otherapp']), 1)
-        # Right number of actions?
-        migration = changes['otherapp'][0]
-        self.assertEqual(len(migration.operations), 1)
-        # Right action?
-        action = migration.operations[0]
-        self.assertEqual(action.__class__.__name__, "AlterField")
-        self.assertEqual(action.name, "author")
-        self.assertEqual(action.field.rel.to, "testapp.Writer")
+        # Now that RenameModel handles related fields too, there should be
+        # no AlterField for the related field.
+        self.assertNumberMigrations(changes, 'otherapp', 0)
 
     def test_rename_model_with_renamed_rel_field(self):
         """
@@ -316,9 +306,8 @@ def test_rename_model_with_renamed_rel_field(self):
         after = self.make_project_state([self.author_renamed_with_book, self.book_with_field_and_author_renamed])
         autodetector = MigrationAutodetector(before, after, MigrationQuestioner({"ask_rename_model": True, "ask_rename": True}))
         changes = autodetector._detect_changes()
-
         # Right number of migrations for model rename?
-        self.assertEqual(len(changes['testapp']), 1)
+        self.assertNumberMigrations(changes, 'testapp', 1)
         # Right number of actions?
         migration = changes['testapp'][0]
         self.assertEqual(len(migration.operations), 1)
@@ -327,21 +316,17 @@ def test_rename_model_with_renamed_rel_field(self):
         self.assertEqual(action.__class__.__name__, "RenameModel")
         self.assertEqual(action.old_name, "Author")
         self.assertEqual(action.new_name, "Writer")
-
         # Right number of migrations for related field rename?
-        self.assertEqual(len(changes['otherapp']), 1)
+        # Alter is already taken care of.
+        self.assertNumberMigrations(changes, 'otherapp', 1)
         # Right number of actions?
         migration = changes['otherapp'][0]
-        self.assertEqual(len(migration.operations), 2)
+        self.assertEqual(len(migration.operations), 1)
         # Right actions?
         action = migration.operations[0]
         self.assertEqual(action.__class__.__name__, "RenameField")
         self.assertEqual(action.old_name, "author")
         self.assertEqual(action.new_name, "writer")
-        action = migration.operations[1]
-        self.assertEqual(action.__class__.__name__, "AlterField")
-        self.assertEqual(action.name, "writer")
-        self.assertEqual(action.field.rel.to, "testapp.Writer")
 
     def test_fk_dependency(self):
         "Tests that having a ForeignKey automatically adds a dependency"

tests/migrations/test_base.py

@@ -46,3 +46,17 @@ def assertIndexExists(self, table, columns, value=True):
 
     def assertIndexNotExists(self, table, columns):
         return self.assertIndexExists(table, columns, False)
+
+    def assertFKExists(self, table, columns, to, value=True):
+        with connection.cursor() as cursor:
+            self.assertEqual(
+                value,
+                any(
+                    c["foreign_key"] == to
+                    for c in connection.introspection.get_constraints(cursor, table).values()
+                    if c['columns'] == list(columns)
+                ),
+            )
+
+    def assertFKNotExists(self, table, columns, to, value=True):
+        return self.assertFKExists(table, columns, to, False)

tests/migrations/test_operations.py

@@ -245,68 +245,36 @@ def test_rename_model(self):
         """
         Tests the RenameModel operation.
         """
-        project_state = self.set_up_test_model("test_rnmo")
+        project_state = self.set_up_test_model("test_rnmo", related_model=True)
         # Test the state alteration
         operation = migrations.RenameModel("Pony", "Horse")
         new_state = project_state.clone()
         operation.state_forwards("test_rnmo", new_state)
         self.assertNotIn(("test_rnmo", "pony"), new_state.models)
         self.assertIn(("test_rnmo", "horse"), new_state.models)
+        # Remember, RenameModel also repoints all incoming FKs and M2Ms
+        self.assertEqual("test_rnmo.Horse", new_state.models["test_rnmo", "rider"].fields[1][1].rel.to)
         # Test the database alteration
         self.assertTableExists("test_rnmo_pony")
         self.assertTableNotExists("test_rnmo_horse")
+        if connection.features.supports_foreign_keys:
+            self.assertFKExists("test_rnmo_rider", ["pony_id"], ("test_rnmo_pony", "id"))
+            self.assertFKNotExists("test_rnmo_rider", ["pony_id"], ("test_rnmo_horse", "id"))
         with connection.schema_editor() as editor:
             operation.database_forwards("test_rnmo", editor, project_state, new_state)
         self.assertTableNotExists("test_rnmo_pony")
         self.assertTableExists("test_rnmo_horse")
+        if connection.features.supports_foreign_keys:
+            self.assertFKNotExists("test_rnmo_rider", ["pony_id"], ("test_rnmo_pony", "id"))
+            self.assertFKExists("test_rnmo_rider", ["pony_id"], ("test_rnmo_horse", "id"))
         # And test reversal
         with connection.schema_editor() as editor:
             operation.database_backwards("test_rnmo", editor, new_state, project_state)
-        self.assertTableExists("test_dlmo_pony")
+        self.assertTableExists("test_rnmo_pony")
         self.assertTableNotExists("test_rnmo_horse")
-
-    # See #22248 - this will fail until that's fixed.
-    #
-    # def test_rename_model_with_related(self):
-    #     """
-    #     Tests the real-world combo of a RenameModel operation with AlterField
-    #     for a related field.
-    #     """
-    #     project_state = self.set_up_test_model(
-    #         "test_rnmowr", related_model=True)
-    #     # Test the state alterations
-    #     model_operation = migrations.RenameModel("Pony", "Horse")
-    #     new_state = project_state.clone()
-    #     model_operation.state_forwards("test_rnmowr", new_state)
-    #     self.assertNotIn(("test_rnmowr", "pony"), new_state.models)
-    #     self.assertIn(("test_rnmowr", "horse"), new_state.models)
-
-    #     self.assertEqual(
-    #         "Pony",
-    #         project_state.render().get_model("test_rnmowr", "rider")
-    #         ._meta.get_field_by_name("pony")[0].rel.to._meta.object_name)
-    #     field_operation = migrations.AlterField(
-    #         "Rider", "pony", models.ForeignKey("Horse"))
-    #     field_operation.state_forwards("test_rnmowr", new_state)
-    #     self.assertEqual(
-    #         "Horse",
-    #         new_state.render().get_model("test_rnmowr", "rider")
-    #         ._meta.get_field_by_name("pony")[0].rel.to._meta.object_name)
-
-    #     # Test the database alterations
-    #     self.assertTableExists("test_rnmowr_pony")
-    #     self.assertTableNotExists("test_rnmowr_horse")
-    #     with connection.schema_editor() as editor:
-    #         model_operation.database_forwards("test_rnmowr", editor, project_state, new_state)
-    #         field_operation.database_forwards("test_rnmowr", editor, project_state, new_state)
-    #     self.assertTableNotExists("test_rnmowr_pony")
-    #     self.assertTableExists("test_rnmowr_horse")
-    #     # And test reversal
-    #     with connection.schema_editor() as editor:
-    #         field_operation.database_backwards("test_rnmowr", editor, new_state, project_state)
-    #         model_operation.database_backwards("test_rnmowr", editor, new_state, project_state)
-    #     self.assertTableExists("test_rnmowr_pony")
-    #     self.assertTableNotExists("test_rnmowr_horse")
+        if connection.features.supports_foreign_keys:
+            self.assertFKExists("test_rnmo_rider", ["pony_id"], ("test_rnmo_pony", "id"))
+            self.assertFKNotExists("test_rnmo_rider", ["pony_id"], ("test_rnmo_horse", "id"))
 
     def test_add_field(self):
         """