Fixed #22833: Autodetector not doing through mapping correctly

django/db/migrations/autodetector.py

@@ -127,7 +127,11 @@ class MigrationAutodetector(object):
             new_model_state = self.to_state.models[app_label, model_name]
             self.old_field_keys.update((app_label, model_name, x) for x, y in old_model_state.fields)
             self.new_field_keys.update((app_label, model_name, x) for x, y in new_model_state.fields)
-            # Through model stuff
+
+        # Through model map generation
+        for app_label, model_name in sorted(self.old_model_keys):
+            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]
             for field_name, field in old_model_state.fields:
                 old_field = self.old_apps.get_model(app_label, old_model_name)._meta.get_field_by_name(field_name)[0]
                 if hasattr(old_field, "rel") and hasattr(old_field.rel, "through") and not old_field.rel.through._meta.auto_created:

tests/migrations/test_autodetector.py

@@ -750,6 +750,21 @@ class AutodetectorTests(TestCase):
         self.assertEqual(action.__class__.__name__, "DeleteModel")
         self.assertEqual(action.name, "Attribution")
 
+    def test_many_to_many_removed_before_through_model_2(self):
+        """
+        Removing a model that contains a ManyToManyField and the
+        "through" model in the same change must remove
+        the field before the model to maintain consistency.
+        """
+        before = self.make_project_state([self.book_with_multiple_authors_through_attribution, self.author_name, self.attribution])
+        after = self.make_project_state([self.author_name])  # removes both the through model and ManyToMany
+        autodetector = MigrationAutodetector(before, after)
+        changes = autodetector._detect_changes()
+        # Right number of migrations?
+        self.assertNumberMigrations(changes, 'otherapp', 1)
+        # Right number of actions?
+        self.assertOperationTypes(changes, 'otherapp', 0, ["RemoveField", "RemoveField", "RemoveField", "DeleteModel", "DeleteModel"])
+
     def test_m2m_w_through_multistep_remove(self):
         """
         A model with a m2m field that specifies a "through" model cannot be removed in the same