Refs #27666 -- Ensured relationship consistency on delayed reloads.

Delayed reloads of state models broke identity based relationships
between direct and non-direct ancestors.

Basing models.Options related objects map of model labels instead of
their identity ensured relationship consistency is maintained.

Refs #30966.

Co-authored-by: Hasan Ramezani <hasan.r67@gmail.com>

2 files changed, 27 insertions, 2 deletions

diff --git a/django/db/models/options.py b/django/db/models/options.py
index f027a74976..0e28b6812a 100644
--- a/django/db/models/options.py
+++ b/django/db/models/options.py
@@ -698,7 +698,8 @@ class Options:
             )
             for f in fields_with_relations:
                 if not isinstance(f.remote_field.model, str):
-                    related_objects_graph[f.remote_field.model._meta.concrete_model._meta].append(f)
+                    remote_label = f.remote_field.model._meta.concrete_model._meta.label
+                    related_objects_graph[remote_label].append(f)
 
         for model in all_models:
             # Set the relation_tree using the internal __dict__. In this way
@@ -706,7 +707,7 @@ class Options:
             # __dict__ takes precedence over a data descriptor (such as
             # @cached_property). This means that the _meta._relation_tree is
             # only called if related_objects is not in __dict__.
-            related_objects = related_objects_graph[model._meta.concrete_model._meta]
+            related_objects = related_objects_graph[model._meta.concrete_model._meta.label]
             model._meta.__dict__['_relation_tree'] = related_objects
         # It seems it is possible that self is not in all_models, so guard
         # against that with default for get().
diff --git a/tests/migrations/test_state.py b/tests/migrations/test_state.py
index ef198eb0b6..44d4cdf268 100644
--- a/tests/migrations/test_state.py
+++ b/tests/migrations/test_state.py
@@ -532,6 +532,30 @@ class StateTests(SimpleTestCase):
         project_state.add_model(ModelState.from_model(B))
         self.assertEqual(len(project_state.apps.get_models()), 2)
 
+    def test_reload_model_relationship_consistency(self):
+        project_state = ProjectState()
+        project_state.add_model(ModelState('migrations', 'A', []))
+        project_state.add_model(ModelState('migrations', 'B', [
+            ('a', models.ForeignKey('A', models.CASCADE)),
+        ]))
+        project_state.add_model(ModelState('migrations', 'C', [
+            ('b', models.ForeignKey('B', models.CASCADE)),
+        ]))
+        A = project_state.apps.get_model('migrations.A')
+        B = project_state.apps.get_model('migrations.B')
+        C = project_state.apps.get_model('migrations.C')
+        self.assertEqual([r.related_model for r in A._meta.related_objects], [B])
+        self.assertEqual([r.related_model for r in B._meta.related_objects], [C])
+        self.assertEqual([r.related_model for r in C._meta.related_objects], [])
+
+        project_state.reload_model('migrations', 'a', delay=True)
+        A = project_state.apps.get_model('migrations.A')
+        B = project_state.apps.get_model('migrations.B')
+        C = project_state.apps.get_model('migrations.C')
+        self.assertEqual([r.related_model for r in A._meta.related_objects], [B])
+        self.assertEqual([r.related_model for r in B._meta.related_objects], [C])
+        self.assertEqual([r.related_model for r in C._meta.related_objects], [])
+
     def test_add_relations(self):
         """
         #24573 - Adding relations to existing models should reload the