Prevent SkinDataCleanup from deleting SKINDATA entries which were created...

Prevent SkinDataCleanup from deleting SKINDATA entries which were created after the one it was targeted at. (See code comment for complete explanation)


git-svn-id: https://svn.erp5.org/repos/public/erp5/trunk@24556 20353a03-c40f-0410-a6d1-a30d3c3de9de

product/ERP5Type/patches/CMFCoreSkinnable.py

@@ -13,7 +13,7 @@
 ##############################################################################
 
 from Products.CMFCore import Skinnable
-from Products.CMFCore.Skinnable import SKINDATA, superGetAttr, SkinDataCleanup, SkinnableObjectManager
+from Products.CMFCore.Skinnable import SKINDATA, superGetAttr, SkinnableObjectManager
 from thread import get_ident
 from zLOG import LOG, WARNING, DEBUG
 from Acquisition import aq_base
@@ -134,7 +134,7 @@ def CMFCoreSkinnableSkinnableObjectManager_changeSkin(self, skinname):
   SKINDATA[tid] = (skinname, {'portal_skins': None}, {})
   REQUEST = getattr(self, 'REQUEST', None)
   if REQUEST is not None:
-    REQUEST._hold(SkinDataCleanup(tid))
+    REQUEST._hold(SkinDataCleanup(tid, SKINDATA[tid]))
 
 def CMFCoreSkinnableSkinnableObjectManager_getSkin(self, name=None):
   """
@@ -154,3 +154,35 @@ Skinnable.SkinnableObjectManager.getSkin = CMFCoreSkinnableSkinnableObjectManage
 from Products.CMFCore.PortalObject import PortalObjectBase
 PortalObjectBase.__getattr__ = CMFCoreSkinnableSkinnableObjectManager___getattr__
 
+# Redefine SkinDataCleanup completely.
+# This class is designed to remove entries from SKINDATA dictionnary, to avoid
+# keeping references to persistent objects besides transaction boundaries.
+# This cleanup is triggered by deletion of SkinDataCleanup instance, which
+# happens after corresponding REQUEST instance is deleted (because of '_hold'
+# mechanism).
+# But because of the lag which exists between REQUEST deletion and
+# SkinDataCleanup deletion (due to garbage collection), it sometimes deletes a
+# new SKINDATA entry, unrelated to the intended one. This leaves a system with
+# no SKINDATA entry for current thread, leading to errors.
+# A case where it's easy to trigger such error is CMFActivity's REQUEST
+# separation mechanism, where one request is created for each single activity.
+
+class SkinDataCleanup:
+  def __init__(self, tid, skindata):
+    self.tid = tid
+    self.skindata_id = self.hashSkinData(skindata)
+
+  def __del__(self):
+    tid = self.tid
+    skindata = SKINDATA.get(tid)
+    if skindata is not None:
+      if self.hashSkinData(skindata) == self.skindata_id:
+        try:
+          # Entry might have already disapeared. Ignore.
+          del SKINDATA[tid]
+        except KeyError:
+          pass
+
+  def hashSkinData(self, skindata):
+    return id(skindata)
+