[5.1.x] Fixed #35950 -- Restored refreshing of relations when fields deferred.

Thank you to Simon Charette and Sarah Boyce for the review.

Regression in 73df8b54a2.

Backport of 2f6b096b83 from main.

tests/contenttypes_tests/test_fields.py

@@ -57,6 +57,15 @@ class GenericForeignKeyTests(TestCase):
         self.assertIsNot(answer.question, old_question_obj)
         self.assertEqual(answer.question, old_question_obj)
 
+    def test_clear_cached_generic_relation_when_deferred(self):
+        question = Question.objects.create(text="question")
+        Answer.objects.create(text="answer", question=question)
+        answer = Answer.objects.defer("text").get()
+        old_question_obj = answer.question
+        # The reverse relation is refreshed even when the text field is deferred.
+        answer.refresh_from_db()
+        self.assertIsNot(answer.question, old_question_obj)
+
 
 class GenericRelationTests(TestCase):
     def test_value_to_string(self):

tests/defer/tests.py

@@ -290,6 +290,14 @@ class TestDefer2(AssertionMixin, TestCase):
             self.assertEqual(rf2.name, "new foo")
             self.assertEqual(rf2.value, "new bar")
 
+    def test_refresh_when_one_field_deferred(self):
+        s = Secondary.objects.create()
+        PrimaryOneToOne.objects.create(name="foo", value="bar", related=s)
+        s = Secondary.objects.defer("first").get()
+        p_before = s.primary_o2o
+        s.refresh_from_db()
+        self.assertIsNot(s.primary_o2o, p_before)
+
 
 class InvalidDeferTests(SimpleTestCase):
     def test_invalid_defer(self):