Fixed #36701 -- Fixed memory leak in ModelState.

2 files changed, 30 insertions, 0 deletions

diff --git a/tests/model_regress/models.py b/tests/model_regress/models.py
index 350850393a..2af882f20f 100644
--- a/tests/model_regress/models.py
+++ b/tests/model_regress/models.py
@@ -45,6 +45,10 @@ class Worker(models.Model):
         return self.name
 
 
+class WorkerProfile(models.Model):
+    worker = models.OneToOneField(Worker, on_delete=models.CASCADE)
+
+
 class NonAutoPK(models.Model):
     name = models.CharField(max_length=10, primary_key=True)
 
diff --git a/tests/model_regress/test_state.py b/tests/model_regress/test_state.py
index 8b0f087829..8abcc58382 100644
--- a/tests/model_regress/test_state.py
+++ b/tests/model_regress/test_state.py
@@ -1,7 +1,33 @@
+import gc
+
 from django.db.models.base import ModelState, ModelStateFieldsCacheDescriptor
 from django.test import SimpleTestCase
+from django.test.utils import garbage_collect
+
+from .models import Worker, WorkerProfile
 
 
 class ModelStateTests(SimpleTestCase):
     def test_fields_cache_descriptor(self):
         self.assertIsInstance(ModelState.fields_cache, ModelStateFieldsCacheDescriptor)
+
+    def test_one_to_one_field_cycle_collection(self):
+        self.addCleanup(gc.set_debug, gc.get_debug())
+        gc.set_debug(gc.DEBUG_SAVEALL)
+
+        def clear_garbage():
+            del gc.garbage[:]
+
+        self.addCleanup(clear_garbage)
+
+        worker = Worker()
+        profile = WorkerProfile(worker=worker)
+        worker_id = id(worker)
+
+        del worker
+        del profile
+
+        garbage_collect()
+
+        leaked = [obj for obj in gc.garbage if id(obj) == worker_id]
+        self.assertEqual(leaked, [])