Don't include base class __slots__ in subclass construction

CHANGES.md

@@ -24,6 +24,9 @@
   when importing cloudpickle.
   ([issue #337](https://github.com/cloudpipe/cloudpickle/pull/337))
 
+- Fix a bug affecting subclasses of slotted classes.
+  ([issue #311](https://github.com/cloudpipe/cloudpickle/issues/311))
+
 1.2.2
 =====
 

cloudpickle/cloudpickle.py

@@ -640,7 +640,7 @@ def save_dynamic_class(self, obj):
         # doc can't participate in a cycle with the original class.
         type_kwargs = {'__doc__': clsdict.pop('__doc__', None)}
 
-        if hasattr(obj, "__slots__"):
+        if "__slots__" in clsdict:
             type_kwargs['__slots__'] = obj.__slots__
             # pickle string length optimization: member descriptors of obj are
             # created automatically from obj's __slots__ attribute, no need to

cloudpickle/cloudpickle_fast.py

@@ -68,7 +68,7 @@ def dumps(obj, protocol=None, buffer_callback=None):
 
 def _class_getnewargs(obj):
     type_kwargs = {}
-    if hasattr(obj, "__slots__"):
+    if "__slots__" in obj.__dict__:
         type_kwargs["__slots__"] = obj.__slots__
 
     __dict__ = obj.__dict__.get('__dict__', None)
@@ -143,7 +143,7 @@ def _class_getstate(obj):
         (registry, _, _, _) = abc._get_dump(obj)
         clsdict["_abc_impl"] = [subclass_weakref()
                                 for subclass_weakref in registry]
-    if hasattr(obj, "__slots__"):
+    if "__slots__" in clsdict:
         # pickle string length optimization: member descriptors of obj are
         # created automatically from obj's __slots__ attribute, no need to
         # save them in obj's state

tests/cloudpickle_test.py

@@ -1842,6 +1842,17 @@ def __init__(self):
                 with pytest.raises(AttributeError):
                     obj.non_registered_attribute = 1
 
+            class SubclassWithSlots(ClassWithSlots):
+                def __init__(self):
+                    self.unregistered_attribute = 1
+
+            obj = SubclassWithSlots()
+            s = cloudpickle.dumps(obj, protocol=self.protocol)
+            del SubclassWithSlots
+            depickled_obj = cloudpickle.loads(s)
+            assert depickled_obj.unregistered_attribute == 1
+
+
     @unittest.skipIf(not hasattr(types, "MappingProxyType"),
                      "Old versions of Python do not have this type.")
     def test_mappingproxy(self):