bazarr/libs/stevedore/driver.py

146 lines
5.9 KiB
Python

# 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.
from .exception import NoMatches, MultipleMatches
from .named import NamedExtensionManager
class DriverManager(NamedExtensionManager):
"""Load a single plugin with a given name from the namespace.
:param namespace: The namespace for the entry points.
:type namespace: str
:param name: The name of the driver to load.
:type name: str
: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 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, name,
invoke_on_load=False, invoke_args=(), invoke_kwds={},
on_load_failure_callback=None,
verify_requirements=False):
on_load_failure_callback = on_load_failure_callback \
or self._default_on_load_failure
super(DriverManager, self).__init__(
namespace=namespace,
names=[name],
invoke_on_load=invoke_on_load,
invoke_args=invoke_args,
invoke_kwds=invoke_kwds,
on_load_failure_callback=on_load_failure_callback,
verify_requirements=verify_requirements,
)
@staticmethod
def _default_on_load_failure(drivermanager, ep, err):
raise
@classmethod
def make_test_instance(cls, extension, namespace='TESTING',
propagate_map_exceptions=False,
on_load_failure_callback=None,
verify_requirements=False):
"""Construct a test DriverManager
Test instances are passed a list of extensions to work from rather
than loading them from entry points.
:param extension: Pre-configured Extension instance
:type extension: :class:`~stevedore.extension.Extension`
:param namespace: The namespace for the manager; used only for
identification since the extensions are passed in.
:type namespace: str
: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
:return: The manager instance, initialized for testing
"""
o = super(DriverManager, cls).make_test_instance(
[extension], namespace=namespace,
propagate_map_exceptions=propagate_map_exceptions,
on_load_failure_callback=on_load_failure_callback,
verify_requirements=verify_requirements)
return o
def _init_plugins(self, extensions):
super(DriverManager, self)._init_plugins(extensions)
if not self.extensions:
name = self._names[0]
raise NoMatches('No %r driver found, looking for %r' %
(self.namespace, name))
if len(self.extensions) > 1:
discovered_drivers = ','.join(e.entry_point_target
for e in self.extensions)
raise MultipleMatches('Multiple %r drivers found: %s' %
(self.namespace, discovered_drivers))
def __call__(self, func, *args, **kwds):
"""Invokes func() for the single loaded extension.
The signature for func() should be::
def func(ext, *args, **kwds):
pass
The first argument to func(), 'ext', is the
:class:`~stevedore.extension.Extension` instance.
Exceptions raised from within func() are logged and ignored.
:param func: Callable to invoke for each extension.
:param args: Variable arguments to pass to func()
:param kwds: Keyword arguments to pass to func()
:returns: List of values returned from func()
"""
results = self.map(func, *args, **kwds)
if results:
return results[0]
@property
def driver(self):
"""Returns the driver being used by this manager.
"""
ext = self.extensions[0]
return ext.obj if ext.obj else ext.plugin