[1.5.x] Fixed #14694 -- Made ``defer()`` work with reverse relations

Reverse o2o fields are now usable with defer.

Backpatch of [6ebf115206289bce8f3d86318871faac13d6e835]

2 files changed, 34 insertions, 1 deletions

diff --git a/tests/regressiontests/defer_regress/models.py b/tests/regressiontests/defer_regress/models.py
index 444649ac92..7528e3b2c9 100644
--- a/tests/regressiontests/defer_regress/models.py
+++ b/tests/regressiontests/defer_regress/models.py
@@ -55,6 +55,10 @@ class Feature(models.Model):
 class SpecialFeature(models.Model):
     feature = models.ForeignKey(Feature)
 
+class OneToOneItem(models.Model):
+    item = models.OneToOneField(Item, related_name="one_to_one_item")
+    name = models.CharField(max_length=15)
+
 class ItemAndSimpleItem(models.Model):
     item = models.ForeignKey(Item)
     simple = models.ForeignKey(SimpleItem)
diff --git a/tests/regressiontests/defer_regress/tests.py b/tests/regressiontests/defer_regress/tests.py
index c77ca32135..964e4dc7c7 100644
--- a/tests/regressiontests/defer_regress/tests.py
+++ b/tests/regressiontests/defer_regress/tests.py
@@ -9,7 +9,7 @@ from django.db.models.loading import cache
 from django.test import TestCase
 
 from .models import (ResolveThis, Item, RelatedItem, Child, Leaf, Proxy,
-    SimpleItem, Feature, ItemAndSimpleItem, SpecialFeature)
+    SimpleItem, Feature, ItemAndSimpleItem, OneToOneItem, SpecialFeature)
 
 
 class DeferRegressionTest(TestCase):
@@ -111,6 +111,7 @@ class DeferRegressionTest(TestCase):
                 Item,
                 ItemAndSimpleItem,
                 Leaf,
+                OneToOneItem,
                 Proxy,
                 RelatedItem,
                 ResolveThis,
@@ -147,6 +148,7 @@ class DeferRegressionTest(TestCase):
                 "Leaf_Deferred_name_value",
                 "Leaf_Deferred_second_child_id_value",
                 "Leaf_Deferred_value",
+                "OneToOneItem",
                 "Proxy",
                 "RelatedItem",
                 "RelatedItem_Deferred_",
@@ -182,6 +184,33 @@ class DeferRegressionTest(TestCase):
         self.assertEqual(1, qs.count())
         self.assertEqual('Foobar', qs[0].name)
 
+    def test_reverse_one_to_one_relations(self):
+        # Refs #14694. Test reverse relations which are known unique (reverse
+        # side has o2ofield or unique FK) - the o2o case
+        item = Item.objects.create(name="first", value=42)
+        o2o = OneToOneItem.objects.create(item=item, name="second")
+        self.assertEqual(len(Item.objects.defer('one_to_one_item__name')), 1)
+        self.assertEqual(len(Item.objects.select_related('one_to_one_item')), 1)
+        self.assertEqual(len(Item.objects.select_related(
+            'one_to_one_item').defer('one_to_one_item__name')), 1)
+        self.assertEqual(len(Item.objects.select_related('one_to_one_item').defer('value')), 1)
+        # Make sure that `only()` doesn't break when we pass in a unique relation,
+        # rather than a field on the relation.
+        self.assertEqual(len(Item.objects.only('one_to_one_item')), 1)
+        with self.assertNumQueries(1):
+            i = Item.objects.select_related('one_to_one_item')[0]
+            self.assertEquals(i.one_to_one_item.pk, o2o.pk)
+            self.assertEquals(i.one_to_one_item.name, "second")
+        with self.assertNumQueries(1):
+            i = Item.objects.select_related('one_to_one_item').defer(
+                'value', 'one_to_one_item__name')[0]
+            self.assertEquals(i.one_to_one_item.pk, o2o.pk)
+            self.assertEquals(i.name, "first")
+        with self.assertNumQueries(1):
+            self.assertEquals(i.one_to_one_item.name, "second")
+        with self.assertNumQueries(1):
+            self.assertEquals(i.value, 42)
+
     def test_defer_with_select_related(self):
         item1 = Item.objects.create(name="first", value=47)
         item2 = Item.objects.create(name="second", value=42)