Fix nasty acquisition related bug that would trigger if an aq-wrapped…

… object had a proper __parent__ pointer and one of its parents did not, leading to infinite recursion

CHANGES.txt

@@ -4,6 +4,14 @@ Changelog
 1.1 - unreleased
 ----------------
 
+* Don't prefer using __parent__ over using aq_parent() to find the parent when
+  looking for a registry. This causes nasty acquisition infinite recursion
+  because doing getattr(obj, '__parent__') when obj supports implicit
+  acquisition gives you back the parent acquisition-wrapped in the child.
+  It's not a problem until some parent *doesn't* have a __parent__ pointer,
+  at which point we end up trying to use aq_parent() and get into a loop.
+  [optilude]
+
 * Made zope.component 3.5 support official and adjusted tests.
 
 1.0 - 2008-11-18

src/five/localsitemanager/utils.py

@@ -1,7 +1,7 @@
 from zope.traversing.interfaces import IContainmentRoot
 
 from Acquisition import aq_parent, aq_inner
-
+from Acquisition.interfaces import IAcquirer
 
 def get_parent(obj):
     """Returns the container the object was traversed via.  This
@@ -16,12 +16,13 @@ def get_parent(obj):
     if IContainmentRoot.providedBy(obj):
         return None
 
+    if IAcquirer.providedBy(obj):
+        parent = aq_parent(aq_inner(obj))
+        if parent is not None:
+            return parent
+
     parent = getattr(obj, '__parent__', None)
     if parent is not None:
         return parent
 
-    parent = aq_parent(aq_inner(obj))
-    if parent is not None:
-        return parent
-
     raise TypeError("Not enough context information to get parent", obj)