Fixed #21010 -- Changed ModelState to only copy _meta.local_fields.

django/db/migrations/state.py

@@ -70,7 +70,7 @@ class ModelState(object):
         """
         # Deconstruct the fields
         fields = []
-        for field in model._meta.fields:
+        for field in model._meta.local_fields:
             name, path, args, kwargs = field.deconstruct()
             field_class = import_by_path(path)
             fields.append((name, field_class(*args, **kwargs)))

tests/migrations/test_state.py

@@ -75,3 +75,22 @@ class StateTests(TestCase):
         new_app_cache = project_state.render()
         self.assertEqual(new_app_cache.get_model("migrations", "Tag")._meta.get_field_by_name("name")[0].max_length, 100)
         self.assertEqual(new_app_cache.get_model("migrations", "Tag")._meta.get_field_by_name("hidden")[0].null, False)
+
+    def test_render_multiple_inheritance(self):
+        # Use a custom app cache to avoid polluting the global one.
+        new_app_cache = BaseAppCache()
+
+        class Book(models.Model):
+            title = models.CharField(max_length=1000)
+
+            class Meta:
+                app_label = "migrations"
+                app_cache = new_app_cache
+
+        class Novel(Book):
+            class Meta:
+                app_label = "migrations"
+                app_cache = new_app_cache
+
+        yet_another_app_cache = BaseAppCache()
+        ModelState.from_model(Novel).render(yet_another_app_cache)