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

Thanks to Anssi for the review.

3 files changed, 12 insertions, 5 deletions

diff --git a/django/db/models/fields/related.py b/django/db/models/fields/related.py
index ac6b8221df..24bab96df6 100644
--- a/django/db/models/fields/related.py
+++ b/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.
diff --git a/django/db/models/fields/related_descriptors.py b/django/db/models/fields/related_descriptors.py
index e9caa2680f..486829386f 100644
--- a/django/db/models/fields/related_descriptors.py
+++ b/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,
diff --git a/django/db/models/options.py b/django/db/models/options.py
index 28c2088630..28773bc0b3 100644
--- a/django/db/models/options.py
+++ b/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().