109 lines
3.3 KiB
Python
109 lines
3.3 KiB
Python
# vim: tabstop=4 shiftwidth=4 softtabstop=4
|
|
|
|
# Copyright 2012 OpenStack Foundation
|
|
#
|
|
# Licensed under the Apache License, Version 2.0 (the "License"); you may
|
|
# not use this file except in compliance with the License. You may obtain
|
|
# a copy of the License at
|
|
#
|
|
# http://www.apache.org/licenses/LICENSE-2.0
|
|
#
|
|
# Unless required by applicable law or agreed to in writing, software
|
|
# distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
|
|
# WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
|
|
# License for the specific language governing permissions and limitations
|
|
# under the License.
|
|
|
|
REGISTRY = {}
|
|
|
|
_future_dependencies = {}
|
|
|
|
|
|
class UnresolvableDependencyException(Exception):
|
|
def __init__(self, name):
|
|
msg = 'Unregistered dependency: %s' % name
|
|
super(UnresolvableDependencyException, self).__init__(msg)
|
|
|
|
|
|
def provider(name):
|
|
"""Register the wrapped dependency provider under the specified name."""
|
|
def wrapper(cls):
|
|
def wrapped(init):
|
|
def __wrapped_init__(self, *args, **kwargs):
|
|
"""Initialize the wrapped object and add it to the registry."""
|
|
init(self, *args, **kwargs)
|
|
REGISTRY[name] = self
|
|
|
|
resolve_future_dependencies(name)
|
|
|
|
return __wrapped_init__
|
|
|
|
cls.__init__ = wrapped(cls.__init__)
|
|
return cls
|
|
|
|
return wrapper
|
|
|
|
|
|
def requires(*dependencies):
|
|
"""Inject specified dependencies from the registry into the instance."""
|
|
def wrapper(self, *args, **kwargs):
|
|
"""Inject each dependency from the registry."""
|
|
self.__wrapped_init__(*args, **kwargs)
|
|
|
|
for dependency in self._dependencies:
|
|
if dependency not in REGISTRY:
|
|
if dependency in _future_dependencies:
|
|
_future_dependencies[dependency] += [self]
|
|
else:
|
|
_future_dependencies[dependency] = [self]
|
|
|
|
continue
|
|
|
|
setattr(self, dependency, REGISTRY[dependency])
|
|
|
|
def wrapped(cls):
|
|
"""Note the required dependencies on the object for later injection.
|
|
|
|
The dependencies of the parent class are combined with that of the
|
|
child class to create a new set of dependencies.
|
|
"""
|
|
existing_dependencies = getattr(cls, '_dependencies', set())
|
|
cls._dependencies = existing_dependencies.union(dependencies)
|
|
if not hasattr(cls, '__wrapped_init__'):
|
|
cls.__wrapped_init__ = cls.__init__
|
|
cls.__init__ = wrapper
|
|
return cls
|
|
|
|
return wrapped
|
|
|
|
|
|
def resolve_future_dependencies(provider_name=None):
|
|
if provider_name:
|
|
targets = _future_dependencies.pop(provider_name, [])
|
|
|
|
for target in targets:
|
|
setattr(target, provider_name, REGISTRY[provider_name])
|
|
|
|
return
|
|
|
|
try:
|
|
for dependency, targets in _future_dependencies.iteritems():
|
|
if dependency not in REGISTRY:
|
|
raise UnresolvableDependencyException(dependency)
|
|
|
|
for target in targets:
|
|
setattr(target, dependency, REGISTRY[dependency])
|
|
finally:
|
|
_future_dependencies.clear()
|
|
|
|
|
|
def reset():
|
|
"""Reset the registry of providers.
|
|
|
|
This is useful for unit testing to ensure that tests don't use providers
|
|
from previous tests.
|
|
"""
|
|
|
|
REGISTRY.clear()
|
|
_future_dependencies.clear()
|