[Interface-dev] overriding InterfaceClass.__call__ and 3.4.2dev

[Jim Fulton]

On Jan 6, 2008, at 12:46 PM, Jean-Paul Calderone wrote:

> Hey,
>
> I just noticed a change between 3.4.1 and 3.4.2dev

3.4.2dev? Wazzat? Do you mean the trunk? I hope there isn't a 3.4.2dev  
release somewhere.

> relating to the __call__
> method of InterfaceClass.  If you override it in 3.4.1, it will be  
> used.  If
> you override it in 3.4.2dev, it won't be.

On the trunk, I get:

   >>> import zope.interface.interface
   >>> class InterfaceClass(zope.interface.interface.InterfaceClass):
   ...     def __call__(self, *args):
   ...         print 'called', self, args
   ...
   >>> IFoo = InterfaceClass('IFoo', (zope.interface.Interface,))
   >>> IFoo(1)
   called <InterfaceClass __main__.IFoo> (1,)
   >>> class IBar(IFoo): pass
   ...
   >>> IBar()
   called <InterfaceClass __main__.IBar> ()
   >>> class ISpam(zope.interface.Interface): pass
   ...
   >>> ISpam()
   Traceback (most recent call last):
     File "<console>", line 1, in ?
   TypeError: function takes at least 1 argument (0 given)
   >>> ISpam.__class__ = InterfaceClass
   >>> ISpam()
   Traceback (most recent call last):
     File "<console>", line 1, in ?
   TypeError: function takes at least 1 argument (0 given)

So overriding through subclassing works just fine.  Overriding through  
assigning the __class__ seems to be broken, although this seems to me  
to be a kind of odd way to override.

...

> Is this an intentional change?

There was a recent change intended to speed application startup that  
broke this. I'm a bit suspicious of this change because it uses  
__setattr__.

>  It breaks a feature of Twisted (in web2).

...

>
> Was this accidental?


I'm sure it was.

We'll fix this.

Jim

--
Jim Fulton
Zope Corporation