New submission from Carsten Klein <carsten.kl...@axn-software.de>:
Scenario:
class deco(object):
def __init__(self, optional = False):
self._optional = optional
def __call__(self, decorated):
decorated.optional = self._optional
return decorated
@deco
class y(object):
pass
will fail decorating the class since y is passed in as the first parameter to
deco.__init__, and deco.__call__ will never be called.
@deco(optional = True)
class y(object):
pass
will succeed.
I wonder why there is a distinction between decorator class w/ arguments and
decorator class w/o arguments?
Guessing that one would like to have a decorator class decorating another class
and also acting as a kind of proxy by implementing a __call__ method, this
could also be achieved by further indirection, provided that it will not break
existing code.
A working alternative would be a decorator function like this:
def deco(_decorated = None, optional = False):
def _wrapped(decorated):
decorated.optional = optional
return decorated
if _decorated is not None:
return _wrapped(decorated)
return _wrapped
Is there a chance that the behavior of the decorator class will be fixed in a
future release?
Expected behavior for the decorator class would be:
if formal parameter list has optional parameters and actual parameter list is
empty and there are no formal mandatory parameters:
if decorator class is callable:
deco = decorator class ()
decor.__call__(decorated)
else:
fall back to old behaviour, requiring the decorator class __init__ method
to have one mandatory parameter
else:
deco = decorator class(actual parameters...)
deco.__call__(decorated)
TIA
----------
components: Interpreter Core
messages: 133171
nosy: carsten.klein
priority: normal
severity: normal
status: open
title: Decorator class with optional arguments and a __call__ method gets not
called when there are no arguments
type: behavior
versions: Python 3.2
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Python tracker <rep...@bugs.python.org>
<http://bugs.python.org/issue11788>
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