Fixed #10811 -- Made assigning unsaved objects to FK, O2O, and GFK raise ValueError.

This prevents silent data loss.

Thanks Aymeric Augustin for the initial patch and Loic Bistuer for the review.

2 files changed, 22 insertions, 1 deletions

diff --git a/tests/one_to_one/models.py b/tests/one_to_one/models.py
index b54cabbaa3..f9c0a40ee0 100644
--- a/tests/one_to_one/models.py
+++ b/tests/one_to_one/models.py
@@ -30,6 +30,10 @@ class Restaurant(models.Model):
         return "%s the restaurant" % self.place.name
 
 
+class Bar(models.Model):
+    place = models.OneToOneField(Place, null=True)
+
+
 @python_2_unicode_compatible
 class Waiter(models.Model):
     restaurant = models.ForeignKey(Restaurant)
diff --git a/tests/one_to_one/tests.py b/tests/one_to_one/tests.py
index d5d955b08e..f0a7a175a7 100644
--- a/tests/one_to_one/tests.py
+++ b/tests/one_to_one/tests.py
@@ -3,7 +3,7 @@ from __future__ import unicode_literals
 from django.db import transaction, IntegrityError
 from django.test import TestCase
 
-from .models import (Place, Restaurant, Waiter, ManualPrimaryKey, RelatedModel,
+from .models import (Place, Restaurant, Bar, Waiter, ManualPrimaryKey, RelatedModel,
     MultiModel)
 
 
@@ -128,3 +128,20 @@ class OneToOneTests(TestCase):
         with self.assertRaises(IntegrityError):
             with transaction.atomic():
                 mm.save()
+
+    def test_unsaved_object(self):
+        """
+        #10811 -- Assigning an unsaved object to a OneToOneField
+        should raise an exception.
+        """
+        place = Place(name='User', address='London')
+        with self.assertRaisesMessage(ValueError,
+                            'Cannot assign "%r": "%s" instance isn\'t saved in the database.'
+                            % (place, Restaurant.place.field.rel.to._meta.object_name)):
+            Restaurant.objects.create(place=place, serves_hot_dogs=True, serves_pizza=False)
+        bar = Bar()
+        p = Place(name='User', address='London')
+        with self.assertRaisesMessage(ValueError,
+                            'Cannot assign "%r": "%s" instance isn\'t saved in the database.'
+                            % (bar, p._meta.object_name)):
+            p.bar = bar