Allow short-circuit traversal for non-proxied dict subclasses

This change is based on
https://code.launchpad.net/~wallyworld/zope.pagetemplate/fix-isinstance/+merge/38499
by Ian Booth.

The original approach in that branch broke tests, because they rely on
subclassing dict with an implementer of ITraversable.  Rather than changing
this, it seems safer to only extend the dict special-case to non-proxied
subclasses.

1 files changed, 22 insertions, 0 deletions

diff --git a/src/zope/pagetemplate/engine.py b/src/zope/pagetemplate/engine.py
index 99634fa..df307e7 100644
--- a/src/zope/pagetemplate/engine.py
+++ b/src/zope/pagetemplate/engine.py
@@ -22,6 +22,7 @@ import sys
 from zope import component
 from zope.interface import implementer
 from zope.component.interfaces import ComponentLookupError
+from zope.proxy import isProxy
 from zope.traversing.interfaces import IPathAdapter, ITraversable
 from zope.traversing.interfaces import TraversalError
 from zope.traversing.adapters import traversePathElement
@@ -66,6 +67,8 @@ class ZopeTraverser(object):
             # special-case dicts for performance reasons
             if getattr(object, '__class__', None) == dict:
                 object = object[name]
+            elif isinstance(object, dict) and not isProxy(object):
+                object = object[name]
             else:
                 object = traversePathElement(object, name, path_items,
                                              request=request)
@@ -386,6 +389,25 @@ class ZopeEngine(ZopeBaseEngine):
         ...
       KeyError: 'keys'
 
+    This special-casing also applies to non-proxied dict subclasses:
+
+      >>> class TraverserDict(dict):
+      ...     def __init__(self):
+      ...         self.item_requested = None
+      ...     def __getitem__(self, item):
+      ...         self.item_requested = item
+      ...         return dict.__getitem__(self, item)
+
+      >>> d = engine.getBaseNames()
+      >>> foo = TraverserDict()
+      >>> d['foo'] = foo
+      >>> foo['bar'] = 'baz'
+      >>> context = engine.getContext(d)
+      >>> context.evaluate('foo/bar')
+      'baz'
+      >>> foo.item_requested
+      'bar'
+
       >>> tearDown()
 
     """