From f5a33e4840d3ad4d1199e99f5a17a9af1d2176f9 Mon Sep 17 00:00:00 2001
From: Raphael Merx <raphaelm@captricity.com>
Date: Wed, 16 Sep 2015 19:49:40 -0700
Subject: [PATCH] Fixed #25296 -- Prevented model related object cache
 pollution when create() fails due to an unsaved object.

---
 django/db/models/base.py  | 3 +++
 tests/one_to_one/tests.py | 5 +++++
 2 files changed, 8 insertions(+)

diff --git a/django/db/models/base.py b/django/db/models/base.py
index 2c4a475cd4..be1cb48df9 100644
--- a/django/db/models/base.py
+++ b/django/db/models/base.py
@@ -643,6 +643,9 @@ class Model(six.with_metaclass(ModelBase)):
                 # constraints aren't supported by the database, there's the
                 # unavoidable risk of data corruption.
                 if obj and obj.pk is None:
+                    # Remove the object from a related instance cache.
+                    if not field.remote_field.multiple:
+                        delattr(obj, field.remote_field.get_cache_name())
                     raise ValueError(
                         "save() prohibited to prevent data loss due to "
                         "unsaved related object '%s'." % field.name
diff --git a/tests/one_to_one/tests.py b/tests/one_to_one/tests.py
index 1319cf0d9b..25d20dc2c9 100644
--- a/tests/one_to_one/tests.py
+++ b/tests/one_to_one/tests.py
@@ -135,9 +135,14 @@ class OneToOneTests(TestCase):
         should raise an exception.
         """
         place = Place(name='User', address='London')
+        with self.assertRaises(Restaurant.DoesNotExist):
+            place.restaurant
         msg = "save() prohibited to prevent data loss due to unsaved related object 'place'."
         with self.assertRaisesMessage(ValueError, msg):
             Restaurant.objects.create(place=place, serves_hot_dogs=True, serves_pizza=False)
+        # place should not cache restaurant
+        with self.assertRaises(Restaurant.DoesNotExist):
+            place.restaurant
 
     def test_reverse_relationship_cache_cascade(self):
         """