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# GNU MediaGoblin -- federated, autonomous media hosting
# Copyright (C) 2011, 2012 MediaGoblin contributors. See AUTHORS.
#
# This program is free software: you can redistribute it and/or modify
# it under the terms of the GNU Affero General Public License as published by
# the Free Software Foundation, either version 3 of the License, or
# (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
# GNU Affero General Public License for more details.
#
# You should have received a copy of the GNU Affero General Public License
# along with this program. If not, see <http://www.gnu.org/licenses/>.
"""
This module implements the plugin api bits and provides the plugin
base.
Two things about things in this module:
1. they should be excessively well documented because we should pull
from this file for the docs
2. they should be well tested
How do plugins work?
====================
Plugins are structured like any Python project. You create a Python package.
In that package, you define a high-level ``__init__.py`` that either defines
or imports modules that define classes that inherit from the ``Plugin`` class.
Additionally, you want a LICENSE file that specifies the license and a
``setup.py`` that specifies the metadata for packaging your plugin. A rough
file structure could look like this::
myplugin/
|- setup.py # plugin project packaging metadata
|- README # holds plugin project information
|- LICENSE # holds license information
|- myplugin/ # plugin package directory
|- __init__.py # imports myplugin.main
|- main.py # code for plugin
Lifecycle
=========
1. All the modules listed as subsections of the ``plugins`` section in
the config file are imported. This causes any ``Plugin`` subclasses in
those modules to be defined and when the classes are defined they get
automatically registered with the ``PluginCache``.
2. After all plugin modules are imported, registered plugin classes are
instantiated and ``setup_plugin`` is called for each plugin object.
Plugins can do any setup they need to do in their ``setup_plugin``
method.
"""
import logging
from mediagoblin import mg_globals
_log = logging.getLogger(__name__)
class PluginCache(object):
"""Cache of plugin things"""
__state = {
# list of plugin classes
"plugin_classes": [],
# list of plugin objects
"plugin_objects": []
}
def clear(self):
"""This is only useful for testing."""
del self.plugin_classes[:]
del self.plugin_objects[:]
def __init__(self):
self.__dict__ = self.__state
def register_plugin_class(self, plugin_class):
"""Registers a plugin class"""
self.plugin_classes.append(plugin_class)
def register_plugin_object(self, plugin_obj):
"""Registers a plugin object"""
self.plugin_objects.append(plugin_obj)
class MetaPluginClass(type):
"""Metaclass for PluginBase derivatives"""
def __new__(cls, name, bases, attrs):
new_class = super(MetaPluginClass, cls).__new__(cls, name, bases, attrs)
parents = [b for b in bases if isinstance(b, MetaPluginClass)]
if not parents:
return new_class
PluginCache().register_plugin_class(new_class)
return new_class
class Plugin(object):
"""Exttend this class for plugins.
Example::
from mediagoblin.tools.pluginapi import Plugin
class MyPlugin(Plugin):
...
def setup_plugin(self):
....
"""
__metaclass__ = MetaPluginClass
def setup_plugin(self):
pass
def get_config(key):
"""Retrieves the configuration for a specified plugin by key
Example:
>>> get_config('mediagoblin.plugins.sampleplugin')
{'foo': 'bar'}
>>> get_config('myplugin')
{}
>>> get_config('flatpages')
{'directory': '/srv/mediagoblin/pages', 'nesting': 1}}
"""
global_config = mg_globals.global_config
plugin_section = global_config.get('plugins', {})
return plugin_section.get(key, {})
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