[PEAK] PyProtocols: TypeError: Ambiguous adapter choice

[luper rouch]

2009/7/10 Sergey Schetinin <maluke at gmail.com>:
> 2009/7/10 luper rouch <luper.rouch at gmail.com>:
>> 2009/7/10 Sergey Schetinin <maluke at gmail.com>:
>>> 2009/7/10 luper rouch <luper.rouch at gmail.com>:
>>>> The following code produces an error:
>>>>
>>>> TypeError: ('Ambiguous adapter choice', <class
>>>> '__main__.FooOneAsFoo'>, <class '__main__.FooTwoAsFoo'>, 2, 2)
>>>>
>>>> --- code begins ---
>>>>
>>>> from protocols import Interface, advise
>>>>
>>>> class IFoo(Interface):
>>>>    pass
>>>>
>>>> class IFooOne(Interface):
>>>>    pass
>>>>
>>>> class IFooTwo(Interface):
>>>>    pass
>>>>
>>>> class FooOneAsFoo(object):
>>>>    advise(
>>>>            instancesProvide=[IFoo],
>>>>            asAdapterForProtocols=[IFooOne]
>>>>        )
>>>>
>>>> class FooTwoAsFoo(object):
>>>>    advise(
>>>>            instancesProvide=[IFoo],
>>>>            asAdapterForProtocols=[IFooTwo]
>>>>        )
>>>>
>>>> class ComposedFoo(object):
>>>>    advise(
>>>>            instancesProvide=[IFooOne, IFooTwo]
>>>>        )
>>>>
>>>> --- code ends ---
>>>>
>>>> Why is it ambiguous to write for example:
>>>>
>>>> foo = FooOneAsFoo(ComposedFoo())
>>>>
>>>> foo has an IFoo interface, adapted from the IFooOne interface of ComposedFoo.
>>>>
>>>
>>> Are you sure it's the "foo = FooOneAsFoo(ComposedFoo())" producing the
>>> error? Could it actually be IFoo(ComposedFoo()) ?
>>>
>>
>> Actually it's the ComposedFoo definition that triggers the error.
>>
>
> I guess I'm wrong, but I remember adapter graph being checked for
> ambiguity when used, not on declarations. PEAK-Rules rebuilds indexes
> when first used, so maybe that's what I'm confusing it with.
>
> Anyway, the adaptation graph is ambiguous, because there are two
> adapters from ComposedFoo type to IFoo protocol with the same weight.
> I'm still not sure why you get the error if not trying to do that
> adaptation.
>

Here is the full traceback:

Traceback (most recent call last):
  File "beuh.py", line 43, in <module>
    class ComposedFoo(object):
  File "/var/lib/python-support/python2.6/peak/util/decorators.py",
line 435, in advise
    return decorator(newClass)
  File "/var/lib/python-support/python2.6/protocols/api.py", line 225,
in callback
    instancesDoNotProvide=instancesDoNotProvide
  File "/var/lib/python-support/python2.6/protocols/api.py", line 149,
in declareImplementation
    declareAdapterForType(proto, NO_ADAPTER_NEEDED, typ)
  File "/var/lib/python-support/python2.6/protocols/api.py", line 95,
in declareAdapterForType
    typ, adapter, depth
  File "/var/lib/python-support/python2.6/protocols/interfaces.py",
line 144, in registerImplementation
    proto, composeAdapters(adapter,self,extender), klass, depth+d
  File "/var/lib/python-support/python2.6/protocols/api.py", line 95,
in declareAdapterForType
    typ, adapter, depth
  File "/var/lib/python-support/python2.6/protocols/interfaces.py",
line 129, in registerImplementation
    self.__adapters,klass,adapter,depth
  File "/var/lib/python-support/python2.6/protocols/adapters.py", line
215, in updateWithSimplestAdapter
    new = minimumAdapter(old,adapter,oldDepth,depth)
  File "/var/lib/python-support/python2.6/protocols/adapters.py", line
122, in minimumAdapter
    raise TypeError("Ambiguous adapter choice", a1, a2, d1, d2)
TypeError: ('Ambiguous adapter choice', <class
'__main__.FooOneAsFoo'>, <class '__main__.FooTwoAsFoo'>, 2, 2)

-- 
Lup