Added ReferencField handling with .distinct()

Closes #356

AUTHORS

@@ -84,3 +84,4 @@ that much better:
  * dave mankoff
  * Alexander G. Morano
  * jwilder
+ * Joe Shaw

docs/changelog.rst

@@ -5,6 +5,7 @@ Changelog
 Changes in dev
 ==============
 
+- Added support for DBRefs in distinct()
 - Fixed issue saving False booleans
 - Fixed issue with dynamic documents deltas
 - Added Reverse Delete Rule support to ListFields - MapFields aren't supported

mongoengine/queryset.py

@@ -1073,8 +1073,10 @@ class QuerySet(object):
         :param field: the field to select distinct values from
 
         .. versionadded:: 0.4
+        .. versionchanged:: 0.5 - Fixed handling references
         """
-        return self._cursor.distinct(field)
+        from dereference import dereference
+        return dereference(self._cursor.distinct(field), 1)
 
     def only(self, *fields):
         """Load only a subset of this document's fields. ::

tests/queryset.py

@@ -1958,6 +1958,24 @@ class QuerySetTest(unittest.TestCase):
         self.assertEqual(set(self.Person.objects(age=30).distinct('name')),
                          set(['Mr Orange', 'Mr Pink']))
 
+    def test_distinct_handles_references(self):
+        class Foo(Document):
+            bar = ReferenceField("Bar")
+
+        class Bar(Document):
+            text = StringField()
+
+        Bar.drop_collection()
+        Foo.drop_collection()
+
+        bar = Bar(text="hi")
+        bar.save()
+
+        foo = Foo(bar=bar)
+        foo.save()
+
+        self.assertEquals(Foo.objects.distinct("bar"), [bar])
+
     def test_custom_manager(self):
         """Ensure that custom QuerySetManager instances work as expected.
         """