[1.7.x] Fixed #23630 -- Made AlterModelTable rename auto-created M2M tables.

Thanks Naddiseo for the report, Andrew Godwin for guidance,
and Shai Berger for review.

Backport of 41b337efa0 from master

django/db/migrations/operations/models.py

@@ -212,6 +212,14 @@ class AlterModelTable(Operation):
                 old_model._meta.db_table,
                 new_model._meta.db_table,
             )
+            # Rename M2M fields whose name is based on this model's db_table
+            for (old_field, new_field) in zip(old_model._meta.local_many_to_many, new_model._meta.local_many_to_many):
+                if new_field.rel.through._meta.auto_created:
+                    schema_editor.alter_db_table(
+                        new_field.rel.through,
+                        old_field.rel.through._meta.db_table,
+                        new_field.rel.through._meta.db_table,
+                    )
 
     def database_backwards(self, app_label, schema_editor, from_state, to_state):
         return self.database_forwards(app_label, schema_editor, from_state, to_state)

docs/releases/1.7.2.txt

@@ -9,4 +9,5 @@ Django 1.7.2 fixes several bugs in 1.7.1.
 Bugfixes
 ========
 
-* ... (:ticket:`00000`).
+* Fixed migration's renaming of auto-created many-to-many tables when changing
+  :attr:`Meta.db_table <django.db.models.Options.db_table>` (:ticket:`23630`).

tests/migrations/test_operations.py

@@ -46,7 +46,9 @@ class OperationTestBase(MigrationTestBase):
         operation.state_forwards(app_label, new_state)
         return project_state, new_state
 
-    def set_up_test_model(self, app_label, second_model=False, third_model=False, related_model=False, mti_model=False, proxy_model=False, unique_together=False, options=False):
+    def set_up_test_model(self, app_label, second_model=False, third_model=False,
+            related_model=False, mti_model=False, proxy_model=False,
+            unique_together=False, options=False, db_table=None):
         """
         Creates a test model state and database table.
         """
@@ -82,6 +84,8 @@ class OperationTestBase(MigrationTestBase):
         }
         if options:
             model_options["permissions"] = [("can_groom", "Can groom")]
+        if db_table:
+            model_options["db_table"] = db_table
         operations = [migrations.CreateModel(
             "Pony",
             [
@@ -875,6 +879,37 @@ class OperationTests(OperationTestBase):
             operation.database_backwards("test_almota", editor, new_state, project_state)
         self.assertTableExists("test_almota_pony")
 
+    def test_alter_model_table_m2m(self):
+        """
+        AlterModelTable should rename auto-generated M2M tables.
+        """
+        app_label = "test_talflmltlm2m"
+        pony_db_table = 'pony_foo'
+        project_state = self.set_up_test_model(app_label, second_model=True, db_table=pony_db_table)
+        # Add the M2M field
+        first_state = project_state.clone()
+        operation = migrations.AddField("Pony", "stables", models.ManyToManyField("Stable"))
+        operation.state_forwards(app_label, first_state)
+        with connection.schema_editor() as editor:
+            operation.database_forwards(app_label, editor, project_state, first_state)
+        original_m2m_table = "%s_%s" % (pony_db_table, "stables")
+        new_m2m_table = "%s_%s" % (app_label, "pony_stables")
+        self.assertTableExists(original_m2m_table)
+        self.assertTableNotExists(new_m2m_table)
+        # Rename the Pony db_table which should also rename the m2m table.
+        second_state = first_state.clone()
+        operation = migrations.AlterModelTable(name='pony', table=None)
+        operation.state_forwards(app_label, second_state)
+        with connection.schema_editor() as editor:
+            operation.database_forwards(app_label, editor, first_state, second_state)
+        self.assertTableExists(new_m2m_table)
+        self.assertTableNotExists(original_m2m_table)
+        # And test reversal
+        with connection.schema_editor() as editor:
+            operation.database_backwards(app_label, editor, second_state, first_state)
+        self.assertTableExists(original_m2m_table)
+        self.assertTableNotExists(new_m2m_table)
+
     def test_alter_field(self):
         """
         Tests the AlterField operation.