[Zope3-dev] Interface.Implements module still broken for 2.2 metaclasses

[Phillip J. Eby]

I still feel like we're not really communicating here.  As far as I can 
see, this is a clear and present bug, with an equally clear and present 
fix.  I've presented the basis of both a test case and a patch.  What am I 
missing?


At 10:05 PM 7/7/02 +0100, Steve Alexander wrote:

>Ideally, they should, although that still doesn't deal with rolling your 
>own metaclass that doesn't derive from a standard class type. I don't 
>think there's a particularly elegant way to deal with that, though. yagni.

True, I don't need metaclasses that aren't derived from type.  I *do* need 
metaclasses that *are* derived from type, and that's *not* a YAGNI for me, 
because I've been using them for some time now.

A previous version of the Interface package broke on the same thing, but I 
came up with a clever descriptor-based work-around that fooled the 
Interface package into doing the right thing (after a previous posting 
about the problem on this list failed to produce a response).  But the 
Z3-to-2.6 backport of Interface appears to bypass my work-around.


>>This change would only affect proxies which happened to be around classes 
>>-- and the change would simply make them *work* on such proxies once 
>>isinstance() uses __class__!
>
>Indeed. But in Python2.2.x, isinstance() doesn't use __class__. Right now, 
>Zope3 is being developed using Python 2.2.x.

Right, I get that.  I'm using the Interface package for PEAK, with Python 
2.2.  I assume it benefits the cause of Zope to have the Interface package 
become a Python standard.  I've been working very hard to make TransWarp 
and PEAK work with Interface package versions released with official 
versions of Zope (e.g. 2.6 in this case), in order to keep it simple for 
people to use both my code and the Interface package.  But if it won't work 
with even trivial metaclasses, it doesn't help very much.

At this point, I've decided to go ahead and bundle a copy of the Interface 
package with PEAK so I can guarantee that people can download something 
that works.  :(  In this case, a patched version of Interface that includes 
the metaclass fix.