Hello Jim, Jim Fulton wrote at 2008-1-7 15:15 -0500:
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I think I understand the behavior -- and I think it is a "zope.interface" bug.
No, it is intended behavior.
Why?
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Under some circumstances "zope.interface" adds a "__provides__" descriptor to a class. The descriptor is implemented in "zope/interface/_zope_interface_coptimizations.c" and called "CPB_descr_get".
While "__implements__" is inherited by derived classes, the inherited "__provides__" refuses to work for a derived class and raises "AttributeError: __provides__" instead, the AttriuteError, I observe....
That is intentional.
If "__implements__" is inherited, why is "__provides__" not inherited?
I will try to make my failure independent of "ManagableIndex" and then file a bug report.
I'm unclear why this caused a problem for you. You never said, afaict, what actually broke for you. What expectation did you have that is unsatisfied?
"inspect" does no longer work reliably. "inspect.getmembers" and "inspect.classify_class_attrs" require that for each "name" in "dir(cls)" "getattr(cls, name)" does not raise an exception. This fails for classes magically stuffed with a "__provides__" descriptor. As a consequence, "pydoc" (which sits on top of inspect) fails -- and therefore "dm.zdoc".
My main gripe with the way this works is that classes get mutated. If I ever redo this someday, I'd use a data structure external to the classes. Modifying the classes was a mistake.
Yes. That, too, would have avoided the bug. -- Dieter