[Zope-CMF] Re: Delete trouble

[Philipp von Weitershausen]

Martin Aspeli wrote:
> Traceback (innermost last):
>   Module ZPublisher.Publish, line 119, in publish
>   Module ZPublisher.mapply, line 88, in mapply
>   Module ZPublisher.Publish, line 42, in call_object
>   Module OFS.ObjectManager, line 524, in manage_delObjects
>   Module OFS.ObjectManager, line 379, in _delObject
>   Module zope.event, line 23, in notify
>   Module zope.component.event, line 26, in dispatch
>   Module zope.component._api, line 130, in subscribers
>   Module zope.component.registry, line 290, in subscribers
>   Module zope.interface.adapter, line 535, in subscribers
>   Module zope.component.event, line 33, in objectEventNotify
>   Module zope.component._api, line 130, in subscribers
>   Module zope.component.registry, line 290, in subscribers
>   Module zope.interface.adapter, line 535, in subscribers
>   Module OFS.subscribers, line 108, in dispatchObjectWillBeMovedEvent
>   Module zope.app.container.contained, line 182, in dispatchToSublocations
>   Module zope.component._api, line 130, in subscribers
>   Module zope.component.registry, line 290, in subscribers
>   Module zope.interface.adapter, line 535, in subscribers
>   Module OFS.subscribers, line 108, in dispatchObjectWillBeMovedEvent
>   Module zope.app.container.contained, line 182, in dispatchToSublocations
>   Module zope.component._api, line 130, in subscribers
>   Module zope.component.registry, line 290, in subscribers
>   Module zope.interface.adapter, line 535, in subscribers
>   Module Products.CMFCore.CMFCatalogAware, line 285, in 
> dispatchToOpaqueItems
>   Module zope.component._api, line 130, in subscribers
>   Module zope.component.registry, line 290, in subscribers
>   Module zope.interface.adapter, line 535, in subscribers
>   Module Products.CMFCore.CMFCatalogAware, line 306, in 
> handleOpaqueItemEvent
>   Module Products.CMFUid.UniqueIdAnnotationTool, line 87, in 
> manage_beforeDelete
>   Module zope.component._api, line 207, in getUtility
> ComponentLookupError: (<InterfaceClass 
> Products.CMFUid.interfaces.IUniqueIdAnnotationManagement>, '')

The UniqueIDAnnotationTool should probably do a *query*Utility (which 
will return None in case the utility can't be found) and simply not do 
anything in such a case. The canonical way of expressing such fail-safe 
routines is therefore:

   component = query{Utility|Adapter|MultiAdapter}(...)
   if component is not None:
       ...


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