105 lines
3.6 KiB
Python
105 lines
3.6 KiB
Python
#
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# 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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"""Utilities to dynamically load plugin modules.
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Modules imported this way remain accessible to static imports, regardless of
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the order in which they are imported. For modules that are not part of an
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existing package tree, use create_subpackage() to dynamically create a package
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for them before loading them.
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"""
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import pkgutil
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import sys
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import types
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from oslo_log import log as logging
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import six
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LOG = logging.getLogger(__name__)
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def _module_name(*components):
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"""Assemble a fully-qualified module name from its components."""
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return '.'.join(components)
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def create_subpackage(path, parent_package_name, subpackage_name="plugins"):
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"""Dynamically create a package into which to load plugins.
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This allows us to not include an __init__.py in the plugins directory. We
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must still create a package for plugins to go in, otherwise we get warning
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messages during import. This also provides a convenient place to store the
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path(s) to the plugins directory.
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"""
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package_name = _module_name(parent_package_name, subpackage_name)
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package = types.ModuleType(package_name)
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package.__path__ = ([path] if isinstance(path, six.string_types)
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else list(path))
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sys.modules[package_name] = package
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return package
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def _import_module(importer, module_name, package):
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"""Import a module dynamically into a package.
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:param importer: PEP302 Importer object (which knows the path to look in).
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:param module_name: the name of the module to import.
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:param package: the package to import the module into.
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"""
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# Duplicate copies of modules are bad, so check if this has already been
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# imported statically
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if module_name in sys.modules:
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return sys.modules[module_name]
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loader = importer.find_module(module_name)
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if loader is None:
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return None
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module = loader.load_module(module_name)
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# Make this accessible through the parent package for static imports
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local_name = module_name.partition(package.__name__ + '.')[2]
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module_components = local_name.split('.')
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parent = six.moves.reduce(getattr, module_components[:-1], package)
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setattr(parent, module_components[-1], module)
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return module
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def load_modules(package, ignore_error=False):
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"""Dynamically load all modules from a given package."""
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path = package.__path__
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pkg_prefix = package.__name__ + '.'
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for importer, module_name, is_package in pkgutil.walk_packages(path,
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pkg_prefix):
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# Skips tests or setup packages so as not to load tests in general
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# or setup.py during doc generation.
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if '.tests.' in module_name or module_name.endswith('.setup'):
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continue
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try:
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module = _import_module(importer, module_name, package)
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except ImportError:
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LOG.error('Failed to import module %s', module_name)
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if not ignore_error:
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raise
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else:
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if module is not None:
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yield module
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