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On 08/10/2011 07:09 AM, Alan Elkner wrote:
Hey Justas, I'm getting a strange error when I enter the url of localhost:7080/gradebook/templates which should try to rneder the index.html view of the IGradebookTemplates providing object. The object is arrived at via two traversal adapters found in the gradebook's configure.html. The registrations use the adapterTraverserPlugin directive which does the adapter traversal correctly as evidenced by the error message. However, adapterTraverserPlugin probably doesn't set __parent__ on the adapted context (please check this for me), so the exception occurs when, for some reason, a viewlet is looking for the parent of the templates (see backtrace).
An interesting case indeed. The fault was within getGradebookTemplates adapter.
It was calling zope.container.contained.contained during traversal to locate gradebook templates within GradebookRoot. localhost:7080/gradebook/templates/index.html was faulty (not implemented) and raised and exception, that consequentially reverted the transaction and led to the error page; the error page could not be rendered correctly, because templates.__parent__ was reset by reverted transaction.
This is a good example why modifying essential objects while traversing is not the best idea.
Also - zope.container.contained.contained is a helper method for tests and does not fire containment events - please use it with caution, or better - avoid it (I think I started using it first as a hack :/ ).
Anyway - fix committed, along with evolution script. Cheers, Justas
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