Let z.s.checker.Global objects be pickled when security-proxied under…

… PyPy with zope.proxy 4.1.5

CHANGES.rst

@@ -4,7 +4,7 @@ Changes
 4.0.2 (unreleased)
 ------------------
 
-- TBD
+- Compatibility with ``zope.proxy`` 4.1.5 under PyPy.
 
 4.0.1 (2014-03-19)
 ------------------

src/zope/security/proxy.py

@@ -84,11 +84,34 @@ def __getattribute__(self, name):
         checker = super(PyProxyBase, self).__getattribute__('_checker')
         if name == '_checker':
             return checker
-        if name not in ['__cmp__', '__hash__', '__bool__', '__nonzero__',
+        if name not in ('__cmp__', '__hash__', '__bool__', '__nonzero__',
                         '__lt__', '__le__', '__eq__', '__ne__', '__ge__',
-                        '__gt__']:
+                        '__gt__'):
             checker.check_getattr(wrapped, name)
-        return checker.proxy(super(ProxyPy, self).__getattribute__(name))
+        if name in ('__reduce__', '__reduce_ex__'):
+            # The superclass specifically denies access to __reduce__
+            # and __reduce__ex__, not letting proxies be pickled. But
+            # for backwards compatibility, we need to be able to
+            # pickle proxies. See checker:Global for an example.
+            val = getattr(wrapped, name)
+        elif name == '__module__':
+            # The superclass deals with descriptors found in the type
+            # of this object just like the Python language spec states, letting
+            # them have precedence over things found in the instance. This
+            # normally makes us a better proxy implementation. However, the
+            # C version of this code in _proxy doesn't take that same care and instead
+            # uses the generic object attribute access methods directly on
+            # the wrapped object. This is a behaviour difference; so far, it's
+            # only been noticed for the __module__ attribute, which checker:Global
+            # wants to override but couldn't because this object's type's __module__ would
+            # get in the way. That broke pickling, and checker:Global can't return
+            # anything more sophisticated than a str (a tuple) because it gets proxied
+            # and breaks pickling again. Our solution is to match the C version for this
+            # one attribute.
+            val = getattr(wrapped, name)
+        else:
+            val = super(ProxyPy, self).__getattribute__(name)
+        return checker.proxy(val)
 
     def __getattr__(self, name):
         wrapped = super(PyProxyBase, self).__getattribute__('_wrapped')