92 lines
3.0 KiB
Python
92 lines
3.0 KiB
Python
# vim: tabstop=4 shiftwidth=4 softtabstop=4
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#
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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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'''
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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 heat.openstack.common import log as logging
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logger = 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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'''
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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, basestring) 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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'''
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Import a module dynamically into the specified package, given its name and
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PEP302 Importer object (which knows the path to look in).
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'''
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fullname = _module_name(package.__name__, module_name)
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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 fullname in sys.modules:
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return sys.modules[fullname]
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loader = importer.find_module(fullname)
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if loader is None:
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return None
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module = loader.load_module(fullname)
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# Make this accessible through the parent package for static imports
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setattr(package, module_name, 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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for importer, module_name, is_package in pkgutil.walk_packages(path):
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try:
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module = _import_module(importer, module_name, package)
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except ImportError as ex:
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logger.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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