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# Copyright (C) 2009-2011 by the Free Software Foundation, Inc.
#
# This file is part of GNU Mailman.
#
# GNU Mailman 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.
#
# GNU Mailman 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
# GNU Mailman. If not, see <http://www.gnu.org/licenses/>.
"""Find various kinds of object in package space."""
from __future__ import absolute_import, unicode_literals
__metaclass__ = type
__all__ = [
'find_components',
]
import os
import sys
from pkg_resources import resource_listdir
def find_components(package, interface):
"""Find components which conform to a given interface.
Search all the modules in a given package, returning an iterator over all
objects found that conform to the given interface.
:param package: The package path to search.
:type package: string
:param interface: The interface that returned objects must conform to.
:type interface: `Interface`
:return: The sequence of matching components.
:rtype: objects implementing `interface`
"""
for filename in resource_listdir(package, ''):
basename, extension = os.path.splitext(filename)
if extension != '.py':
continue
module_name = '{0}.{1}'.format(package, basename)
__import__(module_name, fromlist='*')
module = sys.modules[module_name]
if not hasattr(module, '__all__'):
continue
for name in module.__all__:
missing = object()
component = getattr(module, name, missing)
assert component is not missing, (
'%s has bad __all__: %s' % (module, name))
if interface.implementedBy(component):
yield component
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