Fixed Doc.objects(read_preference=X) not setting read preference (#352)

docs/changelog.rst

@@ -5,6 +5,7 @@ Changelog
 
 Changes in 0.8.2
 ================
+- Fixed Doc.objects(read_preference=X) not setting read preference (#352)
 - Django session ttl index expiry fixed (#329)
 - Fixed pickle.loads (#342)
 - Documentation fixes

mongoengine/queryset/queryset.py

@@ -104,13 +104,17 @@ class QuerySet(object):
                 raise InvalidQueryError(msg)
             query &= q_obj
 
+        if read_preference is None:
             queryset = self.clone()
+        else:
+            # Use the clone provided when setting read_preference
+            queryset = self.read_preference(read_preference)
+
         queryset._query_obj &= query
         queryset._mongo_query = None
         queryset._cursor_obj = None
-        if read_preference is not None:
-            queryset.read_preference(read_preference)
         queryset._class_check = class_check
+
         return queryset
 
     def __len__(self):

tests/queryset/queryset.py

@@ -3100,6 +3100,9 @@ class QuerySetTest(unittest.TestCase):
         self.assertRaises(ConfigurationError, Bar.objects,
                           read_preference='Primary')
 
+        bars = Bar.objects(read_preference=ReadPreference.SECONDARY_PREFERRED)
+        self.assertEqual(bars._read_preference, ReadPreference.SECONDARY_PREFERRED)
+
     def test_json_simple(self):
 
         class Embedded(EmbeddedDocument):