[1.8.x] Fixed #25786 -- Fixed set_FOO_order() crash with order_with_respect_to…

[1.8.x] Fixed #25786 -- Fixed set_FOO_order() crash with order_with_respect_to referencing OneToOneField pk.

Partial backport of 7bec480f from master

django/db/models/base.py

@@ -1674,13 +1674,13 @@ class Model(six.with_metaclass(ModelBase)):
 def method_set_order(ordered_obj, self, id_list, using=None):
     if using is None:
         using = DEFAULT_DB_ALIAS
-    rel_val = getattr(self, ordered_obj._meta.order_with_respect_to.rel.field_name)
-    order_name = ordered_obj._meta.order_with_respect_to.name
+    order_wrt = ordered_obj._meta.order_with_respect_to
+    filter_args = order_wrt.get_forward_related_filter(self)
     # FIXME: It would be nice if there was an "update many" version of update
     # for situations like this.
     with transaction.atomic(using=using, savepoint=False):
         for i, j in enumerate(id_list):
-            ordered_obj.objects.filter(**{'pk': j, order_name: rel_val}).update(_order=i)
+            ordered_obj.objects.filter(pk=j, **filter_args).update(_order=i)
 
 
 def method_get_order(ordered_obj, self):

django/db/models/fields/related.py

@@ -314,6 +314,19 @@ class RelatedField(Field):
         else:
             self.do_related_class(other, cls)
 
+    def get_forward_related_filter(self, obj):
+        """
+        Return the keyword arguments that when supplied to
+        self.model.object.filter(), would select all instances related through
+        this field to the remote obj. This is used to build the querysets
+        returned by related descriptors. obj is an instance of
+        self.related_field.model.
+        """
+        return {
+            '%s__%s' % (self.name, rh_field.name): getattr(obj, rh_field.attname)
+            for _, rh_field in self.related_fields
+        }
+
     @property
     def swappable_setting(self):
         """

docs/releases/1.8.7.txt

@@ -42,3 +42,7 @@ Bugfixes
 
 * Fixed a duplicate query regression in 1.8 on proxied model deletion
   (:ticket:`25685`).
+
+* Fixed ``set_FOO_order()`` crash when the ``ForeignKey`` of a model with
+  ``order_with_respect_to`` references a model with a ``OneToOneField``
+  primary key (:ticket:`25786`).

tests/order_with_respect_to/models.py

@@ -33,3 +33,19 @@ class Post(models.Model):
 
     def __str__(self):
         return self.title
+
+
+# order_with_respect_to points to a model with a OneToOneField primary key.
+class Entity(models.Model):
+    pass
+
+
+class Dimension(models.Model):
+    entity = models.OneToOneField('Entity', primary_key=True)
+
+
+class Component(models.Model):
+    dimension = models.ForeignKey('Dimension')
+
+    class Meta:
+        order_with_respect_to = 'dimension'

tests/order_with_respect_to/tests.py

@@ -5,7 +5,7 @@ from operator import attrgetter
 from django.db import models
 from django.test import TestCase
 
-from .models import Answer, Post, Question
+from .models import Answer, Dimension, Entity, Post, Question
 
 
 class OrderWithRespectToTests(TestCase):
@@ -103,3 +103,13 @@ class OrderWithRespectToTests2(TestCase):
                 count += 1
 
         self.assertEqual(count, 1)
+
+
+class TestOrderWithRespectToOneToOnePK(TestCase):
+    def test_set_order(self):
+        e = Entity.objects.create()
+        d = Dimension.objects.create(entity=e)
+        c1 = d.component_set.create()
+        c2 = d.component_set.create()
+        d.set_component_order([c1.id, c2.id])
+        self.assertQuerysetEqual(d.component_set.all(), [c1.id, c2.id], attrgetter('pk'))