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##############################################################################
#
# Copyright (c) 2012 Zope Foundation and Contributors.
# All Rights Reserved.
#
# This software is subject to the provisions of the Zope Public License,
# Version 2.1 (ZPL). A copy of the ZPL should accompany this distribution.
# THIS SOFTWARE IS PROVIDED "AS IS" AND ANY AND ALL EXPRESS OR IMPLIED
# WARRANTIES ARE DISCLAIMED, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
# WARRANTIES OF TITLE, MERCHANTABILITY, AGAINST INFRINGEMENT, AND FITNESS
# FOR A PARTICULAR PURPOSE.
#
##############################################################################
class implementer_if_needed:
# Helper to make sure we don't redundantly implement
# interfaces already inherited. Doing so tends to produce
# problems with the C3 order. In this package, we could easily
# statically determine to elide the relevant interfaces, but
# this is a defense against changes in parent classes and lessens
# the testing burden.
def __init__(self, *ifaces):
self._ifaces = ifaces
def __call__(self, cls):
from zope.interface import implementedBy
from zope.interface import implementer
ifaces_needed = []
implemented = implementedBy(cls)
ifaces_needed = [
iface
for iface in self._ifaces
if not implemented.isOrExtends(iface)
]
return implementer(*ifaces_needed)(cls)
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