160 lines
7.1 KiB
Python
160 lines
7.1 KiB
Python
# Licensed under the Apache License, Version 2.0 (the "License"); you may
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# not use this file except in compliance with the License. You may obtain
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# a copy of the License at
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#
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# http://www.apache.org/licenses/LICENSE-2.0
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#
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# Unless required by applicable law or agreed to in writing, software
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# distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
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# WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
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# License for the specific language governing permissions and limitations
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# under the License.
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import logging
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from .extension import ExtensionManager
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LOG = logging.getLogger(__name__)
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class NamedExtensionManager(ExtensionManager):
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"""Loads only the named extensions.
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This is useful for explicitly enabling extensions in a
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configuration file, for example.
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:param namespace: The namespace for the entry points.
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:type namespace: str
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:param names: The names of the extensions to load.
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:type names: list(str)
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:param invoke_on_load: Boolean controlling whether to invoke the
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object returned by the entry point after the driver is loaded.
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:type invoke_on_load: bool
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:param invoke_args: Positional arguments to pass when invoking
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the object returned by the entry point. Only used if invoke_on_load
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is True.
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:type invoke_args: tuple
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:param invoke_kwds: Named arguments to pass when invoking
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the object returned by the entry point. Only used if invoke_on_load
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is True.
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:type invoke_kwds: dict
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:param name_order: If true, sort the loaded extensions to match the
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order used in ``names``.
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:type name_order: bool
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:param propagate_map_exceptions: Boolean controlling whether exceptions
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are propagated up through the map call or whether they are logged and
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then ignored
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:type propagate_map_exceptions: bool
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:param on_load_failure_callback: Callback function that will be called when
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an entrypoint can not be loaded. The arguments that will be provided
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when this is called (when an entrypoint fails to load) are
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(manager, entrypoint, exception)
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:type on_load_failure_callback: function
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:param on_missing_entrypoints_callback: Callback function that will be
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called when one or more names cannot be found. The provided argument
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will be a subset of the 'names' parameter.
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:type on_missing_entrypoints_callback: function
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:param verify_requirements: Use setuptools to enforce the
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dependencies of the plugin(s) being loaded. Defaults to False.
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:type verify_requirements: bool
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:param warn_on_missing_entrypoint: Flag to control whether failing
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to load a plugin is reported via a log mess. Only applies if
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on_missing_entrypoints_callback is None.
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:type warn_on_missing_entrypoint: bool
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"""
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def __init__(self, namespace, names,
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invoke_on_load=False, invoke_args=(), invoke_kwds={},
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name_order=False, propagate_map_exceptions=False,
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on_load_failure_callback=None,
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on_missing_entrypoints_callback=None,
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verify_requirements=False,
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warn_on_missing_entrypoint=True):
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self._init_attributes(
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namespace, names, name_order=name_order,
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propagate_map_exceptions=propagate_map_exceptions,
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on_load_failure_callback=on_load_failure_callback)
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extensions = self._load_plugins(invoke_on_load,
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invoke_args,
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invoke_kwds,
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verify_requirements)
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self._missing_names = set(names) - set([e.name for e in extensions])
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if self._missing_names:
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if on_missing_entrypoints_callback:
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on_missing_entrypoints_callback(self._missing_names)
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elif warn_on_missing_entrypoint:
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LOG.warning('Could not load %s' %
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', '.join(self._missing_names))
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self._init_plugins(extensions)
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@classmethod
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def make_test_instance(cls, extensions, namespace='TESTING',
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propagate_map_exceptions=False,
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on_load_failure_callback=None,
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verify_requirements=False):
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"""Construct a test NamedExtensionManager
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Test instances are passed a list of extensions to use rather than
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loading them from entry points.
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:param extensions: Pre-configured Extension instances
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:type extensions: list of :class:`~stevedore.extension.Extension`
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:param namespace: The namespace for the manager; used only for
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identification since the extensions are passed in.
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:type namespace: str
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:param propagate_map_exceptions: Boolean controlling whether exceptions
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are propagated up through the map call or whether they are logged
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and then ignored
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:type propagate_map_exceptions: bool
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:param on_load_failure_callback: Callback function that will
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be called when an entrypoint can not be loaded. The
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arguments that will be provided when this is called (when
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an entrypoint fails to load) are (manager, entrypoint,
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exception)
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:type on_load_failure_callback: function
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:param verify_requirements: Use setuptools to enforce the
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dependencies of the plugin(s) being loaded. Defaults to False.
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:type verify_requirements: bool
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:return: The manager instance, initialized for testing
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"""
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o = cls.__new__(cls)
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names = [e.name for e in extensions]
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o._init_attributes(namespace, names,
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propagate_map_exceptions=propagate_map_exceptions,
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on_load_failure_callback=on_load_failure_callback)
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o._init_plugins(extensions)
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return o
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def _init_attributes(self, namespace, names, name_order=False,
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propagate_map_exceptions=False,
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on_load_failure_callback=None):
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super(NamedExtensionManager, self)._init_attributes(
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namespace, propagate_map_exceptions=propagate_map_exceptions,
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on_load_failure_callback=on_load_failure_callback)
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self._names = names
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self._missing_names = set()
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self._name_order = name_order
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def _init_plugins(self, extensions):
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super(NamedExtensionManager, self)._init_plugins(extensions)
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if self._name_order:
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self.extensions = [self[n] for n in self._names
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if n not in self._missing_names]
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def _load_one_plugin(self, ep, invoke_on_load, invoke_args, invoke_kwds,
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verify_requirements):
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# Check the name before going any further to prevent
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# undesirable code from being loaded at all if we are not
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# going to use it.
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if ep.name not in self._names:
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return None
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return super(NamedExtensionManager, self)._load_one_plugin(
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ep, invoke_on_load, invoke_args, invoke_kwds,
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verify_requirements,
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)
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