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# 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
# 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.
import logging
from .extension import ExtensionManager
LOG = logging.getLogger(__name__)
class EnabledExtensionManager(ExtensionManager):
"""Loads only plugins that pass a check function.
The check_func argument should return a boolean, with ``True``
indicating that the extension should be loaded and made available
and ``False`` indicating that the extension should be ignored.
:param namespace: The namespace for the entry points.
:type namespace: str
:param check_func: Function to determine which extensions to load.
:type check_func: callable, taking an :class:`Extension`
instance as argument
:param invoke_on_load: Boolean controlling whether to invoke the
object returned by the entry point after the driver is loaded.
:type invoke_on_load: bool
:param invoke_args: Positional arguments to pass when invoking
the object returned by the entry point. Only used if invoke_on_load
is True.
:type invoke_args: tuple
:param invoke_kwds: Named arguments to pass when invoking
the object returned by the entry point. Only used if invoke_on_load
is True.
:type invoke_kwds: dict
:param propagate_map_exceptions: Boolean controlling whether exceptions
are propagated up through the map call or whether they are logged and
then ignored
:type propagate_map_exceptions: bool
:param on_load_failure_callback: Callback function that will be called when
a entrypoint can not be loaded. The arguments that will be provided
when this is called (when an entrypoint fails to load) are
(manager, entrypoint, exception)
:type on_load_failure_callback: function
:param verify_requirements: Use setuptools to enforce the
dependencies of the plugin(s) being loaded. Defaults to False.
:type verify_requirements: bool
def __init__(self, namespace, check_func, invoke_on_load=False,
invoke_args=(), invoke_kwds={},
self.check_func = check_func
super(EnabledExtensionManager, self).__init__(
def _load_one_plugin(self, ep, invoke_on_load, invoke_args, invoke_kwds,
ext = super(EnabledExtensionManager, self)._load_one_plugin(
ep, invoke_on_load, invoke_args, invoke_kwds,
if ext and not self.check_func(ext):
LOG.debug('ignoring extension %r',
return None
return ext