Fixed #18012 -- Propagated reverse foreign keys from proxy to concrete models.

Thanks to Anssi for the review.

django/db/models/fields/related.py

@@ -684,7 +684,7 @@ class ForeignObject(RelatedField):
         # Internal FK's - i.e., those with a related name ending with '+' -
         # and swapped models don't get a related descriptor.
         if not self.remote_field.is_hidden() and not related.related_model._meta.swapped:
-            setattr(cls, related.get_accessor_name(), self.related_accessor_class(related))
+            setattr(cls._meta.concrete_model, related.get_accessor_name(), self.related_accessor_class(related))
             # While 'limit_choices_to' might be a callable, simply pass
             # it along for later - this is too early because it's still
             # model load time.

django/db/models/fields/related_descriptors.py

@@ -198,7 +198,7 @@ class ForwardManyToOneDescriptor(object):
                 'Cannot assign None: "%s.%s" does not allow null values.' %
                 (instance._meta.object_name, self.field.name)
             )
-        elif value is not None and not isinstance(value, self.field.remote_field.model):
+        elif value is not None and not isinstance(value, self.field.remote_field.model._meta.concrete_model):
             raise ValueError(
                 'Cannot assign "%r": "%s.%s" must be a "%s" instance.' % (
                     value,

django/db/models/options.py

@@ -552,15 +552,20 @@ class Options(object):
         is set as a property on every model.
         """
         related_objects_graph = defaultdict(list)
+        # Map of concrete models to all options of models it represents.
+        # Including its options and all its proxy model ones.
+        concrete_model_classes = defaultdict(list)
 
         all_models = self.apps.get_models(include_auto_created=True)
         for model in all_models:
+            opts = model._meta
+            concrete_model_classes[opts.concrete_model].append(opts)
             # Abstract model's fields are copied to child models, hence we will
             # see the fields from the child models.
-            if model._meta.abstract:
+            if opts.abstract:
                 continue
             fields_with_relations = (
-                f for f in model._meta._get_fields(reverse=False, include_parents=False)
+                f for f in opts._get_fields(reverse=False, include_parents=False)
                 if f.is_relation and f.related_model is not None
             )
             for f in fields_with_relations:
@@ -573,7 +578,9 @@ class Options(object):
             # __dict__ takes precedence over a data descriptor (such as
             # @cached_property). This means that the _meta._relation_tree is
             # only called if related_objects is not in __dict__.
-            related_objects = related_objects_graph[model._meta]
+            related_objects = list(chain.from_iterable(
+                related_objects_graph[opts] for opts in concrete_model_classes[model]
+            ))
             model._meta.__dict__['_relation_tree'] = related_objects
         # It seems it is possible that self is not in all_models, so guard
         # against that with default for get().

docs/releases/1.10.txt

@@ -163,7 +163,11 @@ Migrations
 Models
 ^^^^^^
 
-* ...
+* Reverse foreign keys from proxy models are now propagated to their
+  concrete class. The reverse relation attached by a
+  :class:`~django.db.models.ForeignKey` pointing to a proxy model is now
+  accessible as a descriptor on the proxied model class and may be referenced in
+  queryset filtering.
 
 Requests and Responses
 ^^^^^^^^^^^^^^^^^^^^^^

tests/model_meta/models.py

@@ -113,7 +113,7 @@ class Relating(models.Model):
 
     # ForeignKey to ProxyPerson
     proxyperson = models.ForeignKey(ProxyPerson, models.CASCADE, related_name='relating_proxyperson')
-    proxyperson_hidden = models.ForeignKey(ProxyPerson, models.CASCADE, related_name='+')
+    proxyperson_hidden = models.ForeignKey(ProxyPerson, models.CASCADE, related_name='relating_proxyperson_hidden+')
 
     # ManyToManyField to BasePerson
     basepeople = models.ManyToManyField(BasePerson, related_name='relating_basepeople')

tests/model_meta/results.py

@@ -331,6 +331,8 @@ TEST_RESULTS = {
             ('friends_inherited_rel_+', None),
             ('relating_people', None),
             ('relating_person', None),
+            ('relating_proxyperson', None),
+            ('relating_proxyperson_hidden+', None),
         ),
         BasePerson: (
             ('+', None),
@@ -413,6 +415,8 @@ TEST_RESULTS = {
             ('relating_baseperson', BasePerson),
             ('relating_people', None),
             ('relating_person', None),
+            ('relating_proxyperson', None),
+            ('relating_proxyperson_hidden+', None),
         ),
         BasePerson: (
             ('+', None),
@@ -465,6 +469,7 @@ TEST_RESULTS = {
             ('followers_concrete', None),
             ('relating_person', None),
             ('relating_people', None),
+            ('relating_proxyperson', None),
         ),
         BasePerson: (
             ('followers_abstract', None),
@@ -494,6 +499,7 @@ TEST_RESULTS = {
             ('followers_concrete', None),
             ('relating_person', None),
             ('relating_people', None),
+            ('relating_proxyperson', None),
         ),
         BasePerson: (
             ('followers_abstract', None),

tests/proxy_models/models.py

@@ -158,7 +158,7 @@ class ProxyTrackerUser(TrackerUser):
 @python_2_unicode_compatible
 class Issue(models.Model):
     summary = models.CharField(max_length=255)
-    assignee = models.ForeignKey(ProxyTrackerUser, models.CASCADE)
+    assignee = models.ForeignKey(ProxyTrackerUser, models.CASCADE, related_name='issues')
 
     def __str__(self):
         return ':'.join((self.__class__.__name__, self.summary,))

tests/proxy_models/tests.py

@@ -6,7 +6,7 @@ from django.apps import apps
 from django.contrib import admin
 from django.contrib.auth.models import User as AuthUser
 from django.contrib.contenttypes.models import ContentType
-from django.core import checks, exceptions, management
+from django.core import checks, management
 from django.core.urlresolvers import reverse
 from django.db import DEFAULT_DB_ALIAS, models
 from django.db.models import signals
@@ -332,14 +332,19 @@ class ProxyModelTests(TestCase):
         self.assertEqual(resp.name, 'New South Wales')
 
     def test_filter_proxy_relation_reverse(self):
-        tu = TrackerUser.objects.create(
-            name='Contributor', status='contrib')
-        with self.assertRaises(exceptions.FieldError):
-            TrackerUser.objects.filter(issue=None),
+        tu = TrackerUser.objects.create(name='Contributor', status='contrib')
+        ptu = ProxyTrackerUser.objects.get()
+        issue = Issue.objects.create(assignee=tu)
+        self.assertEqual(tu.issues.get(), issue)
+        self.assertEqual(ptu.issues.get(), issue)
         self.assertQuerysetEqual(
-            ProxyTrackerUser.objects.filter(issue=None),
+            TrackerUser.objects.filter(issues=issue),
             [tu], lambda x: x
         )
+        self.assertQuerysetEqual(
+            ProxyTrackerUser.objects.filter(issues=issue),
+            [ptu], lambda x: x
+        )
 
     def test_proxy_bug(self):
         contributor = ProxyTrackerUser.objects.create(name='Contributor',