Fixed #22239 -- Add auto detection of renamed models

django/db/migrations/autodetector.py

@@ -61,6 +61,48 @@ def _detect_changes(self):
             for al, mn in self.to_state.models.keys()
             if not new_apps.get_model(al, mn)._meta.proxy
         ]
+
+        def _rel_agnostic_fields_def(fields):
+            """
+            Return a definition of the fields that ignores field names and
+            what related fields actually relate to.
+            """
+            fields_def = []
+            for name, field in fields:
+                deconstruction = field.deconstruct()[1:]
+                if field.rel and field.rel.to:
+                    del deconstruction[2]['to']
+                fields_def.append(deconstruction)
+            return fields_def
+
+        # Find any renamed models.
+        renamed_models = {}
+        renamed_models_rel = {}
+        added_models = set(new_model_keys) - set(old_model_keys)
+        for app_label, model_name in added_models:
+            model_state = self.to_state.models[app_label, model_name]
+            model_fields_def = _rel_agnostic_fields_def(model_state.fields)
+
+            removed_models = set(old_model_keys) - set(new_model_keys)
+            for rem_app_label, rem_model_name in removed_models:
+                if rem_app_label == app_label:
+                    rem_model_state = self.from_state.models[rem_app_label, rem_model_name]
+                    rem_model_fields_def = _rel_agnostic_fields_def(rem_model_state.fields)
+                    if model_fields_def == rem_model_fields_def:
+                        if self.questioner.ask_rename_model(rem_model_state, model_state):
+                            self.add_to_migration(
+                                app_label,
+                                operations.RenameModel(
+                                    old_name=rem_model_name,
+                                    new_name=model_name,
+                                )
+                            )
+                            renamed_models[app_label, model_name] = rem_model_name
+                            renamed_models_rel['%s.%s' % (rem_model_state.app_label, rem_model_state.name)] = '%s.%s' % (model_state.app_label, model_state.name)
+                            old_model_keys.remove((rem_app_label, rem_model_name))
+                            old_model_keys.append((app_label, model_name))
+                            break
+
         # Adding models. Phase 1 is adding models with no outward relationships.
         added_models = set(new_model_keys) - set(old_model_keys)
         pending_add = {}
@@ -180,7 +222,8 @@ def _detect_changes(self):
         new_fields = set()
         unique_together_operations = []
         for app_label, model_name in kept_models:
-            old_model_state = self.from_state.models[app_label, model_name]
+            old_model_name = 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]
             # Collect field changes for later global dealing with (so AddFields
             # always come before AlterFields even on separate models)
@@ -197,16 +240,23 @@ def _detect_changes(self):
                     )
                 ))
         # New fields
+        renamed_fields = {}
         for app_label, model_name, field_name in new_fields - old_fields:
-            old_model_state = self.from_state.models[app_label, model_name]
+            old_model_name = 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]
             field = new_model_state.get_field_by_name(field_name)
             # Scan to see if this is actually a rename!
             field_dec = field.deconstruct()[1:]
             found_rename = False
             for rem_app_label, rem_model_name, rem_field_name in (old_fields - new_fields):
                 if rem_app_label == app_label and rem_model_name == model_name:
-                    if old_model_state.get_field_by_name(rem_field_name).deconstruct()[1:] == field_dec:
+                    old_field_dec = old_model_state.get_field_by_name(rem_field_name).deconstruct()[1:]
+                    if field.rel and field.rel.to:
+                        old_rel_to = old_field_dec[2]['to']
+                        if old_rel_to in renamed_models_rel:
+                            old_field_dec[2]['to'] = renamed_models_rel[old_rel_to]
+                    if old_field_dec == field_dec:
                         if self.questioner.ask_rename(model_name, rem_field_name, field_name, field):
                             self.add_to_migration(
                                 app_label,
@@ -217,7 +267,8 @@ def _detect_changes(self):
                                 )
                             )
                             old_fields.remove((rem_app_label, rem_model_name, rem_field_name))
-                            new_fields.remove((app_label, model_name, field_name))
+                            old_fields.add((app_label, model_name, field_name))
+                            renamed_fields[app_label, model_name, field_name] = rem_field_name
                             found_rename = True
                             break
             if found_rename:
@@ -250,7 +301,8 @@ def _detect_changes(self):
                     self.add_swappable_dependency(app_label, swappable_setting)
         # Old fields
         for app_label, model_name, field_name in old_fields - new_fields:
-            old_model_state = self.from_state.models[app_label, model_name]
+            old_model_name = 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]
             self.add_to_migration(
                 app_label,
@@ -262,10 +314,12 @@ def _detect_changes(self):
         # The same fields
         for app_label, model_name, field_name in old_fields.intersection(new_fields):
             # Did the field change?
-            old_model_state = self.from_state.models[app_label, model_name]
+            old_model_name = 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_dec = old_model_state.get_field_by_name(field_name).deconstruct()
-            new_field_dec = new_model_state.get_field_by_name(field_name).deconstruct()
+            old_field_name = renamed_fields.get((app_label, model_name, field_name), field_name)
+            old_field_dec = old_model_state.get_field_by_name(old_field_name).deconstruct()[1:]
+            new_field_dec = new_model_state.get_field_by_name(field_name).deconstruct()[1:]
             if old_field_dec != new_field_dec:
                 self.add_to_migration(
                     app_label,

django/db/migrations/questioner.py

@@ -56,6 +56,10 @@ def ask_rename(self, model_name, old_name, new_name, field_instance):
         "Was this field really renamed?"
         return self.defaults.get("ask_rename", False)
 
+    def ask_rename_model(self, old_model_state, new_model_state):
+        "Was this model really renamed?"
+        return self.defaults.get("ask_rename_model", False)
+
     def ask_merge(self, app_label):
         "Do you really want to merge these migrations?"
         return self.defaults.get("ask_merge", False)
@@ -123,6 +127,10 @@ def ask_rename(self, model_name, old_name, new_name, field_instance):
         "Was this field really renamed?"
         return self._boolean_input("Did you rename %s.%s to %s.%s (a %s)? [y/N]" % (model_name, old_name, model_name, new_name, field_instance.__class__.__name__), False)
 
+    def ask_rename_model(self, old_model_state, new_model_state):
+        "Was this model really renamed?"
+        return self._boolean_input("Did you rename the %s.%s model to %s? [y/N]" % (old_model_state.app_label, old_model_state.name, new_model_state.name), False)
+
     def ask_merge(self, app_label):
         return self._boolean_input(
             "\nMerging will only work if the operations printed above do not conflict\n" +

tests/migrations/test_autodetector.py

@@ -18,6 +18,7 @@ class AutodetectorTests(TestCase):
     author_name_renamed = ModelState("testapp", "Author", [("id", models.AutoField(primary_key=True)), ("names", models.CharField(max_length=200))])
     author_name_default = ModelState("testapp", "Author", [("id", models.AutoField(primary_key=True)), ("name", models.CharField(max_length=200, default='Ada Lovelace'))])
     author_with_book = ModelState("testapp", "Author", [("id", models.AutoField(primary_key=True)), ("name", models.CharField(max_length=200)), ("book", models.ForeignKey("otherapp.Book"))])
+    author_renamed_with_book = ModelState("testapp", "Writer", [("id", models.AutoField(primary_key=True)), ("name", models.CharField(max_length=200)), ("book", models.ForeignKey("otherapp.Book"))])
     author_with_publisher = ModelState("testapp", "Author", [("id", models.AutoField(primary_key=True)), ("name", models.CharField(max_length=200)), ("publisher", models.ForeignKey("testapp.Publisher"))])
     author_with_custom_user = ModelState("testapp", "Author", [("id", models.AutoField(primary_key=True)), ("name", models.CharField(max_length=200)), ("user", models.ForeignKey("thirdapp.CustomUser"))])
     author_proxy = ModelState("testapp", "AuthorProxy", [], {"proxy": True}, ("testapp.author", ))
@@ -29,6 +30,8 @@ class AutodetectorTests(TestCase):
     other_stable = ModelState("otherapp", "Stable", [("id", models.AutoField(primary_key=True))])
     third_thing = ModelState("thirdapp", "Thing", [("id", models.AutoField(primary_key=True))])
     book = ModelState("otherapp", "Book", [("id", models.AutoField(primary_key=True)), ("author", models.ForeignKey("testapp.Author")), ("title", models.CharField(max_length=200))])
+    book_with_author_renamed = ModelState("otherapp", "Book", [("id", models.AutoField(primary_key=True)), ("author", models.ForeignKey("testapp.Writer")), ("title", models.CharField(max_length=200))])
+    book_with_field_and_author_renamed = ModelState("otherapp", "Book", [("id", models.AutoField(primary_key=True)), ("writer", models.ForeignKey("testapp.Writer")), ("title", models.CharField(max_length=200))])
     book_unique = ModelState("otherapp", "Book", [("id", models.AutoField(primary_key=True)), ("author", models.ForeignKey("testapp.Author")), ("title", models.CharField(max_length=200))], {"unique_together": [("author", "title")]})
     book_unique_2 = ModelState("otherapp", "Book", [("id", models.AutoField(primary_key=True)), ("author", models.ForeignKey("testapp.Author")), ("title", models.CharField(max_length=200))], {"unique_together": [("title", "author")]})
     book_unique_3 = ModelState("otherapp", "Book", [("id", models.AutoField(primary_key=True)), ("newfield", models.IntegerField()), ("author", models.ForeignKey("testapp.Author")), ("title", models.CharField(max_length=200))], {"unique_together": [("title", "newfield")]})
@@ -184,6 +187,73 @@ def test_rename_field(self):
         self.assertEqual(action.old_name, "name")
         self.assertEqual(action.new_name, "names")
 
+    def test_rename_model(self):
+        "Tests autodetection of renamed models"
+        # Make state
+        before = self.make_project_state([self.author_with_book, self.book])
+        after = self.make_project_state([self.author_renamed_with_book, self.book_with_author_renamed])
+        autodetector = MigrationAutodetector(before, after, MigrationQuestioner({"ask_rename_model": True}))
+        changes = autodetector._detect_changes()
+
+        # Right number of migrations for model rename?
+        self.assertEqual(len(changes['testapp']), 1)
+        # Right number of actions?
+        migration = changes['testapp'][0]
+        self.assertEqual(len(migration.operations), 1)
+        # Right action?
+        action = migration.operations[0]
+        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.__name__, "Writer")
+
+    def test_rename_model_with_renamed_rel_field(self):
+        """
+        Tests autodetection of renamed models while simultaneously renaming one
+        of the fields that relate to the renamed model.
+        """
+        # Make state
+        before = self.make_project_state([self.author_with_book, self.book])
+        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)
+        # Right number of actions?
+        migration = changes['testapp'][0]
+        self.assertEqual(len(migration.operations), 1)
+        # Right actions?
+        action = migration.operations[0]
+        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), 2)
+        # 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.__name__, "Writer")
+
     def test_fk_dependency(self):
         "Tests that having a ForeignKey automatically adds a dependency"
         # Make state