Fixed #22207 -- Added support for GenericRelation reverse lookups

GenericRelation now supports an optional related_query_name argument.
Setting related_query_name adds a relation from the related object back to
the content type for filtering, ordering and other query operations.

Thanks to Loic Bistuer for spotting a couple of important issues in
his review.

2 files changed, 28 insertions, 0 deletions

diff --git a/docs/ref/contrib/contenttypes.txt b/docs/ref/contrib/contenttypes.txt
index d01fc6baa5..bc8f538857 100644
--- a/docs/ref/contrib/contenttypes.txt
+++ b/docs/ref/contrib/contenttypes.txt
@@ -373,6 +373,15 @@ Reverse generic relations
 
         This class used to be defined in ``django.contrib.contenttypes.generic``.
 
+    .. attribute:: related_query_name
+
+        .. versionadded:: 1.7
+
+        The relation on the related object back to this object doesn't exist by
+        default. Setting ``related_query_name`` creates a relation from the
+        related object back to this one. This allows querying and filtering
+        from the related object.
+
 If you know which models you'll be using most often, you can also add
 a "reverse" generic relationship to enable an additional API. For example::
 
@@ -392,6 +401,20 @@ be used to retrieve their associated ``TaggedItems``::
     >>> b.tags.all()
     [<TaggedItem: django>, <TaggedItem: python>]
 
+.. versionadded:: 1.7
+
+Defining :class:`~django.contrib.contenttypes.fields.GenericRelation` with
+``related_query_name`` set allows querying from the related object::
+
+    tags = GenericRelation(TaggedItem, related_query_name='bookmarks')
+
+This enables filtering, ordering, and other query operations on ``Bookmark``
+from ``TaggedItem``::
+
+    >>> # Get all tags belonging to books containing `django` in the url
+    >>> TaggedItem.objects.filter(bookmarks__url__contains='django')
+    [<TaggedItem: django>, <TaggedItem: python>]
+
 Just as :class:`~django.contrib.contenttypes.fields.GenericForeignKey`
 accepts the names of the content-type and object-ID fields as
 arguments, so too does
diff --git a/docs/releases/1.7.txt b/docs/releases/1.7.txt
index 4c0457e7c5..6c1ab36c90 100644
--- a/docs/releases/1.7.txt
+++ b/docs/releases/1.7.txt
@@ -1165,6 +1165,11 @@ Miscellaneous
 * The ``shortcut`` view in ``django.contrib.contenttypes.views`` now supports
   protocol-relative URLs (e.g. ``//example.com``).
 
+* :class:`~django.contrib.contenttypes.fields.GenericRelation` now supports an
+  optional ``related_query_name`` argument. Setting ``related_query_name`` adds
+  a relation from the related object back to the content type for filtering,
+  ordering and other query operations.
+
 .. _deprecated-features-1.7:
 
 Features deprecated in 1.7