Restore Folder pickle forward/backward compatibility with 3.12.0

CHANGES.txt

@@ -5,7 +5,8 @@ CHANGES
 4.0.0a3 (unreleased)
 --------------------
 
-- Nothing changed yet.
+- Restore ``Folder`` pickle forward/backward compatibility with
+  version 3.12.0 after making it inherit from ``BTreeContainer.``
 
 
 4.0.0a2 (2013-02-21)
@@ -108,7 +109,7 @@ CHANGES
 
 - Previous releases should be versioned 3.9.0 as they are not pure bugfix
   releases and worth a "feature" release, increasing feature version.
-  
+
   Packages that depend on any changes introduced in version 3.8.2 or 3.8.3
   should depend on version 3.9 or greater.
 
@@ -168,7 +169,7 @@ CHANGES
 3.7.2 (2009-03-12)
 ------------------
 
-- Fix: added missing ComponentLookupError, missing since revision 95429 and 
+- Fix: added missing ComponentLookupError, missing since revision 95429 and
   missing in last release.
 
 - Adapt to the move of IDefaultViewName from zope.component.interfaces

src/zope/container/folder.py

@@ -21,8 +21,8 @@ from zope.container import btree, interfaces
 class Folder(btree.BTreeContainer):
     """The standard Zope Folder implementation."""
 
-    # BBB: The data attribute used to be exposed. This should make it also
-    # compatible with old pickles.
+    # BBB: The data attribute used to be exposed.
+    # For compatibility with existing pickles, we read and write that name
     @property
     def data(self):
         return self._SampleContainer__data
@@ -30,3 +30,15 @@ class Folder(btree.BTreeContainer):
     @data.setter
     def data(self, value):
         self._SampleContainer__data = value
+
+
+    def __getstate__( self ):
+        state = super(Folder,self).__getstate__()
+        data = state.pop( '_SampleContainer__data' )
+        state['data'] = data
+        return state
+
+    def __setstate__( self, state ):
+        if 'data' in state and '_SampleContainer__data' not in state:
+            state['_SampleContainer__data'] = state.pop( 'data' )
+        super(Folder,self).__setstate__( state )

src/zope/container/tests/test_folder.py

@@ -3,6 +3,7 @@ from unittest import TestCase, makeSuite
 from zope.container.folder import Folder
 from zope.container.tests.test_icontainer import TestSampleContainer
 
+import pickle
 
 class Test(TestSampleContainer, TestCase):
 
@@ -15,6 +16,14 @@ class Test(TestSampleContainer, TestCase):
         folder.data = 'foo'
         self.assertEqual(folder.data, 'foo')
 
+    def testPickleCompatibility(self):
+        folder = self.makeTestObject()
+        folder['a'] = 1
+        self.assertEqual( folder.__getstate__()['data'], folder._SampleContainer__data )
+
+        folder_clone = pickle.loads( pickle.dumps( folder ) )
+        self.assertEqual( folder_clone['a'], folder['a'] )
+
+
 def test_suite():
     return makeSuite(Test)
-