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# Copyright (C) 2016 Codethink Limited
# This program is free software; you can redistribute it and/or
# modify it under the terms of the GNU Lesser General Public
# License as published by the Free Software Foundation; either
# version 2 of the License, or (at your option) any later version.
# This library is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# Lesser General Public License for more details.
# You should have received a copy of the GNU Lesser General Public
# License along with this library. If not, see <>.
# Authors:
# Tristan Van Berkom <>
import os
import inspect
from ._exceptions import PluginError
from . import utils
# A Context for loading plugin types
# Args:
# plugin_base (PluginBase): The main PluginBase object to work with
# base_type (type): A base object type for this context
# site_plugin_path (str): Path to where buildstream keeps plugins
# plugin_origins (list): Data used to search for plugins
# Since multiple pipelines can be processed recursively
# within the same interpretor, it's important that we have
# one context associated to the processing of a given pipeline,
# this way sources and element types which are particular to
# a given BuildStream project are isolated to their respective
# Pipelines.
class PluginContext():
def __init__(self, plugin_base, base_type, site_plugin_path, plugin_origins=None, dependencies=None):
# The plugin kinds which were loaded
self.loaded_dependencies = []
# Private members
self._dependencies = dependencies
self._base_type = base_type # The base class plugins derive from
self._types = {} # Plugin type lookup table by kind
self._plugin_origins = plugin_origins or []
# The PluginSource object
self._plugin_base = plugin_base
self._site_source = plugin_base.make_plugin_source(searchpath=site_plugin_path)
self._alternate_sources = {}
# lookup():
# Fetches a type loaded from a plugin in this plugin context
# Args:
# kind (str): The kind of Plugin to create
# Returns: the type associated with the given kind
# Raises: PluginError
def lookup(self, kind):
return self._ensure_plugin(kind)
def _get_local_plugin_source(self, path):
if ('local', path) not in self._alternate_sources:
# key by a tuple to avoid collision
source = self._plugin_base.make_plugin_source(searchpath=[path])
# Ensure that sources never get garbage collected,
# as they'll take the plugins with them.
self._alternate_sources[('local', path)] = source
source = self._alternate_sources[('local', path)]
return source
def _get_pip_plugin_source(self, package_name, kind):
defaults = None
if ('pip', package_name) not in self._alternate_sources:
import pkg_resources
# key by a tuple to avoid collision
package = pkg_resources.get_entry_info(package_name,
except pkg_resources.DistributionNotFound as e:
raise PluginError("Failed to load {} plugin '{}': {}"
.format(self._base_type.__name__, kind, e)) from e
if package is None:
raise PluginError("Pip package {} does not contain a plugin named '{}'"
.format(package_name, kind))
location = package.dist.get_resource_filename(
package.module_name.replace('.', os.sep) + '.py'
# Also load the defaults - required since setuptools
# may need to extract the file.
defaults = package.dist.get_resource_filename(
package.module_name.replace('.', os.sep) + '.yaml'
except KeyError:
# The plugin didn't have an accompanying YAML file
defaults = None
source = self._plugin_base.make_plugin_source(searchpath=[os.path.dirname(location)])
self._alternate_sources[('pip', package_name)] = source
source = self._alternate_sources[('pip', package_name)]
return source, defaults
def _ensure_plugin(self, kind):
if kind not in self._types:
# Check whether the plugin is specified in plugins
source = None
defaults = None
loaded_dependency = False
for origin in self._plugin_origins:
if kind not in origin['plugins']:
if origin['origin'] == 'local':
source = self._get_local_plugin_source(origin['path'])
elif origin['origin'] == 'pip':
source, defaults = self._get_pip_plugin_source(origin['package-name'], kind)
raise PluginError("Failed to load plugin '{}': "
"Unexpected plugin origin '{}'"
.format(kind, origin['origin']))
loaded_dependency = True
# Fall back to getting the source from site
if not source:
if kind not in self._site_source.list_plugins():
raise PluginError("No {} type registered for kind '{}'"
.format(self._base_type.__name__, kind))
source = self._site_source
self._types[kind] = self._load_plugin(source, kind, defaults)
if loaded_dependency:
return self._types[kind]
def _load_plugin(self, source, kind, defaults):
plugin = source.load_plugin(kind)
if not defaults:
plugin_file = inspect.getfile(plugin)
plugin_dir = os.path.dirname(plugin_file)
plugin_conf_name = "{}.yaml".format(kind)
defaults = os.path.join(plugin_dir, plugin_conf_name)
except ImportError as e:
raise PluginError("Failed to load {} plugin '{}': {}"
.format(self._base_type.__name__, kind, e)) from e
plugin_type = plugin.setup()
except AttributeError as e:
raise PluginError("{} plugin '{}' did not provide a setup() function"
.format(self._base_type.__name__, kind)) from e
except TypeError as e:
raise PluginError("setup symbol in {} plugin '{}' is not a function"
.format(self._base_type.__name__, kind)) from e
self._assert_plugin(kind, plugin_type)
self._assert_version(kind, plugin_type)
return (plugin_type, defaults)
def _assert_plugin(self, kind, plugin_type):
if kind in self._types:
raise PluginError("Tried to register {} plugin for existing kind '{}' "
"(already registered {})"
.format(self._base_type.__name__, kind, self._types[kind].__name__))
if not issubclass(plugin_type, self._base_type):
raise PluginError("{} plugin '{}' returned type '{}', which is not a subclass of {}"
.format(self._base_type.__name__, kind,
except TypeError as e:
raise PluginError("{} plugin '{}' returned something that is not a type (expected subclass of {})"
.format(self._base_type.__name__, kind,
self._base_type.__name__)) from e
def _assert_version(self, kind, plugin_type):
# Now assert BuildStream version
bst_major, bst_minor = utils.get_bst_version()
if bst_major < plugin_type.BST_REQUIRED_VERSION_MAJOR or \
(bst_major == plugin_type.BST_REQUIRED_VERSION_MAJOR and
bst_minor < plugin_type.BST_REQUIRED_VERSION_MINOR):
raise PluginError("BuildStream {}.{} is too old for {} plugin '{}' (requires {}.{})"
bst_major, bst_minor,
self._base_type.__name__, kind,