[Zope3-checkins] CVS: Zope3/src/zodb/code - class_.py:1.9

[Jeremy Hylton]

Update of /cvs-repository/Zope3/src/zodb/code
In directory cvs.zope.org:/tmp/cvs-serv19372

Modified Files:
	class_.py 
Log Message:
Fix extend_attr() so that it doesn't provide default values for
attributes that don't exist on the instances.


=== Zope3/src/zodb/code/class_.py 1.8 => 1.9 ===
--- Zope3/src/zodb/code/class_.py:1.8	Fri Jan 24 18:20:56 2003
+++ Zope3/src/zodb/code/class_.py	Tue Jan 28 17:03:43 2003
@@ -30,16 +30,22 @@
 
 class SimpleDescriptor(object):
 
+    missing = object()
+    
     def __init__(self, value):
         self._value = value
 
     def __get__(self, obj, cls):
+        if self._value is self.missing:
+            raise AttributeError
         return self._value
 
     def __set__(self, obj, value):
         self._value = value
 
     def __delete__(self, obj):
+        if self._value is self.missing:
+            raise AttributeError
         del self._value
 
 class ExtClassDescr:
@@ -237,11 +243,11 @@
 
         # helper functions
         def extend_attr(attr, v):
-            prev = findattr(cls, attr, None)
+            prev = findattr(cls, attr, SimpleDescriptor.missing)
             setattr(cls, attr, ExtClassDataDescr(attr, prev, v))
 
         def extend_meth(attr, m):
-            prev = findattr(cls, attr, None)
+            prev = findattr(cls, attr, SimpleDescriptor.missing)
             setattr(cls, attr, ExtClassMethodDescr(attr, prev, m))
 
         extend_attr("_p_oid", None)