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#
# This file is part of Checkbox.
#
# Copyright 2008 Canonical Ltd.
#
# Checkbox is free software: you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation, either version 3 of the License, or
# (at your option) any later version.
#
# Checkbox is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with Checkbox. If not, see <http://www.gnu.org/licenses/>.
#
from inspect import getargspec
from checkbox.lib.decorator import merge_function_metadata
class ArgumentReplacer(object):
"""A decorator helper that filters arguments to be passed to a function.
Create one with the original function and a function to replace
the arguments, and then call replace_arguments for each call to
the function.
"""
def __init__(self, original_function, argument_replacer):
"""
@param original_function: The function which will be called
soon. The function must *not* define any * or ** parameters.
@param argument_replacer: A function which will be called for
every argument. It will be passed a parameter name and the
associated argument. It should return the new value.
"""
self.original_function = original_function
self.argument_replacer = argument_replacer
spec = getargspec(original_function)
self.all_arguments = spec[0]
if getattr(original_function, 'im_self', None) is not None:
# If it's bound, ignore the bound arguments.
self.all_arguments = self.all_arguments[1:]
def replace_arguments(self, args, kwargs):
"""Filter some arguments destined to be passed to a function.
@param args: Original positional arguments.
@param kwargs: Original keyword arguments.
@return: new arguments and kwarguments.
"""
args = list(args)
kwargs = kwargs.copy()
for name_index, name in enumerate(self.all_arguments):
# Ok, we've got the name of the argument. Let's find the value
# of the argument in our original arguments and replace it
# whether it's a positional or a keyword argument.
if name_index < len(args):
# Must be a positional argument
value = args[name_index]
args[name_index] = self.argument_replacer(name, value)
else:
# Must be a keyword argument
if name not in kwargs:
# Oh, but it wasn't passed in. Ignore it.
continue
value = kwargs[name]
kwargs[name] = self.argument_replacer(name, value)
return args, kwargs
def coerce_arguments(**schemas):
"""
A decorator factory which returns a decorator which coerces arguments.
"""
def replacer(name, value):
if name in schemas:
return schemas[name].coerce(value)
return value
def decorator(original):
argument_replacer = ArgumentReplacer(original, replacer)
def replacement(*args, **kwargs):
new_args, new_kwargs = argument_replacer.replace_arguments(args,
kwargs)
return original(*new_args, **new_kwargs)
merge_function_metadata(original, replacement)
return replacement
return decorator
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