Issue #373 : Fix bug with get_real_instances on empty base_result_objects

polymorphic/query.py

@@ -474,7 +474,7 @@ class PolymorphicQuerySet(QuerySet):
         :rtype: PolymorphicQuerySet
         """
         "same as _get_real_instances, but make sure that __repr__ for ShowField... creates correct output"
-        if not base_result_objects:
+        if base_result_objects is None:
             base_result_objects = self
         olist = self._get_real_instances(base_result_objects)
         if not self.model.polymorphic_query_multiline_output:

polymorphic/tests/test_orm.py

@@ -332,6 +332,14 @@ class PolymorphicTests(TransactionTestCase):
             transform=lambda o: o.__class__,
         )
 
+        # from empty list
+        objects = Model2A.objects.get_real_instances([])
+        self.assertQuerysetEqual(
+            objects,
+            [],
+            transform=lambda o: o.__class__,
+        )
+
     def test_translate_polymorphic_q_object(self):
         self.create_model2abcd()