fix add_metaclass when there is a __weakref__ or __dict__ slot (closes #88)

3 files changed, 9 insertions, 2 deletions

diff --git a/CHANGES b/CHANGES
index 056b19e..01c78c4 100644
--- a/CHANGES
+++ b/CHANGES
@@ -6,6 +6,9 @@ This file lists the changes in each six version.
 Development version
 -------------------
 
+- Issue #88: Fix add_metaclass when the class has __slots__ containing
+  "__weakref__" or "__dict__".
+
 - Issue #89: Make six use absolute imports.
 
 - Issue #85: Always accept *updated* and *assigned* arguments for wraps().
diff --git a/six.py b/six.py
index 6940d0d..304f618 100644
--- a/six.py
+++ b/six.py
@@ -719,14 +719,14 @@ def add_metaclass(metaclass):
     """Class decorator for creating a class with a metaclass."""
     def wrapper(cls):
         orig_vars = cls.__dict__.copy()
-        orig_vars.pop('__dict__', None)
-        orig_vars.pop('__weakref__', None)
         slots = orig_vars.get('__slots__')
         if slots is not None:
             if isinstance(slots, str):
                 slots = [slots]
             for slots_var in slots:
                 orig_vars.pop(slots_var)
+        orig_vars.pop('__dict__', None)
+        orig_vars.pop('__weakref__', None)
         return metaclass(cls.__name__, cls.__bases__, orig_vars)
     return wrapper
 
diff --git a/test_six.py b/test_six.py
index 1536276..0125d6b 100644
--- a/test_six.py
+++ b/test_six.py
@@ -730,3 +730,7 @@ def test_add_metaclass():
     py.test.raises(AttributeError, setattr, instance, "a", "baz")
     py.test.raises(AttributeError, setattr, instance, "b", "baz")
 
+    class MySlotsWeakref(object):
+        __slots__ = "__weakref__",
+    MySlotsWeakref = six.add_metaclass(Meta)(MySlotsWeakref)
+    assert type(MySlotsWeakref) is Meta