[Zope3-dev] ComponentLookupError while traversing

[Marius Gedminas]

Hi,

I've noticed the following message produced by a stripped-down Zope 3
instance:

.../Zope3/src/zope/app/traversing/adapters.py:188:
DeprecationWarning: A DefaultTraversable instance raised a NotFoundError
in traverse.  Raising NotFoundError in this method is deprecated and
will no-longer be supported starting in ZopeX3 3.3.  TraversalError
should be raised instead.

It was caused by a page template looking for an undefined menu.
traversePathElement from zope/app/traversing/adapters.py adapts a
MenuAccessView (from zope/app/publisher/browser/menu.py) to ITraversable
and gets a DefaultTraversable instace.  DefaultTraversable.traverse
calls MenuAccessView.__getitem__ which calls zapi.getUtility, which in turn
raises ComponentLookupError.  ComponentLookupError is a subclass of
NotFoundError, and it triggers a DeprecationWarning in traversePathElement.

I'd rather not see that warning, but I'm not sure what the correct solution is.

1. Should MenuAccessView.__getitem__ trap ComponentLookupError and raise
   a KeyError instead?

or

2. Should traversePathElement consider ComponentLookupError to be a
   special case and reraise it without showing a DeprecationWarning?


On a slightly related note, if I call

   foo = traverseName(obj, name, default)

and obj[name] raises a KeyError, should traverseName return 'default',
or should it let the KeyError propagate?


Marius Gedminas
-- 
Gates' Law: Every 18 months, the speed of software halves.
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