[Zope3-dev] TALES PathExpr doesn't call old style classes

[Philipp von Weitershausen]

Dmitry Vasiliev wrote:
> Philipp von Weitershausen wrote:
>> Hi there,
>>
>> I've filed an issue in the collector outlining a problem with old style
>> classes and TALES traversal: http://www.zope.org/Collectors/Zope3-dev/635
>>
>> In particular, I'm looking for comments on problem #2.
> 
> PEP-3100 suggest "just call the object and catch the exception" instead
> of use "callable()". So maybe we can write:
> 
> try:
>     ob()
> except:
>     pass
> return ob
> 
> Unfortunately exceptions still will be masked.

Yes. I honestly have no clue what the authors of this part of PEP3000
were thinking. Even if you only catch AttributeError, you'll never be
sure the AttributeError is from the missing __call__ or from inside it.

callable() isn't even deprecated yet, so if it solves our problem, we
can use it IMO. Note that Zope 3 deliberately doesn't use it because of
the proxy problem. Zope 2 works around that by stripping
proxies/wrappers first (ob.aq_base). Perhaps Zope3 should do that as
well. Would callable(removeAllProxies(obj)) be harmful in any way if you
end up calling the proxied obj() anyway?

Philipp