add a plugin system

A sample plugin can be found in samples/

authentic2/plugins.py

@@ -0,0 +1,77 @@
+"""
+    Use setuptools entrypoints to find plugins
+
+    Propose helper methods to load urls from plugins or modify INSTALLED_APPS
+"""
+import pkg_resources
+import logging
+
+
+from django.conf.urls import patterns, include, url
+
+
+logger = logging.getLogger(__name__)
+
+
+__ALL__ = ['get_plugins']
+
+PLUGIN_CACHE = {}
+
+class PluginError(Exception):
+    pass
+
+def get_plugins(group_name, use_cache=True, *args, **kwargs):
+    '''Traverse all entry points for group_name and instantiate them using args
+       and kwargs.
+    '''
+    global PLUGIN_CACHE
+    if group_name in PLUGIN_CACHE and use_cache:
+        return PLUGIN_CACHE[group_name]
+    plugins = []
+    for entrypoint in pkg_resources.iter_entry_points(group_name):
+        try:
+            plugin_callable = entrypoint.load()
+        except Exception, e:
+            logger.exception('unable to load entrypoint %s', entrypoint)
+            raise PluginError('unable to load entrypoint %s' % entrypoint, e)
+        plugins.append(plugin_callable(*args, **kwargs))
+    PLUGIN_CACHE[group_name] = plugins
+    return plugins
+
+def register_plugins_urls(group_name, urlpatterns):
+    '''Call get_before_urls and get_after_urls on all plugins providing them
+       and add those urls to the given urlpatterns.
+
+       URLs returned by get_before_urls() are added to the head of urlpatterns
+       and those returned by get_after_urls() are added to the tail of
+       urlpatterns.
+    '''
+    plugins = get_plugins(group_name)
+    before_urls = []
+    after_urls = []
+    for plugin in plugins:
+        if hasattr(plugin, 'get_before_urls'):
+            urls = plugin.get_before_urls()
+            before_urls.append(url('^', include(urls)))
+        if hasattr(plugin, 'get_after_urls'):
+            urls = plugin.get_after_urls()
+            after_urls.append(url('^', include(urls)))
+    before_patterns = patterns('', *before_urls)
+    after_patterns = patterns('', *after_urls)
+    return before_patterns + urlpatterns + after_patterns
+
+def register_plugins_installed_apps(group_name, installed_apps):
+    '''Call get_apps() on all plugins of group_name and add the returned
+       applications path to the installed_apps sequence. 
+
+       Applications already present are ignored.
+    '''
+    installed_apps = list(installed_apps)
+    for plugin in get_plugins(group_name):
+        if hasattr(plugin, 'get_apps'):
+            apps = plugin.get_apps()
+            for app in apps:
+                if app not in installed_apps:
+                    installed_apps.append(app)
+    return installed_apps
+

authentic2/settings.py

@@ -1,8 +1,11 @@
 # Django settings for authentic project.
 import os
-from django.core.exceptions import ImproperlyConfigured
 import json
 
+from django.core.exceptions import ImproperlyConfigured
+
+from . import plugins
+
 gettext_noop = lambda s: s
 
 def to_boolean(name, default=True):
@@ -149,6 +152,9 @@ INSTALLED_APPS = (
     'south',
 )
 
+INSTALLED_APPS = plugins.register_plugins_installed_apps('authentic2.plugin',
+        INSTALLED_APPS)
+
 MESSAGE_STORAGE = 'django.contrib.messages.storage.session.SessionStorage'
 
 

authentic2/urls.py

@@ -7,7 +7,7 @@ from authentic2.idp.decorators import prevent_access_to_transient_users
 import authentic2.idp.views
 
 from .admin import admin
-from . import app_settings
+from . import app_settings, plugins
 
 admin.autodiscover()
 handler500 = 'authentic2.views.server_error'
@@ -56,3 +56,5 @@ try:
         )
 except:
     pass
+
+urlpatterns = plugins.register_plugins_urls('authentic2.plugin', urlpatterns)

samples/a2_test_plugin/a2_test_plugin/__init__.py

@@ -0,0 +1,7 @@
+class Plugin(object):
+    def get_before_urls(self):
+        from . import urls
+        return urls.urlpatterns
+
+    def get_apps(self):
+        return [__name__]

samples/a2_test_plugin/a2_test_plugin/models.py

@@ -0,0 +1,4 @@
+from django.db import models
+
+class MyModel(models.Model):
+    a = models.TextField()

samples/a2_test_plugin/a2_test_plugin/urls.py

@@ -0,0 +1,4 @@
+from django.conf.urls import patterns, url
+
+urlpatterns = patterns('a2_test_plugin.views',
+        url('^test/', 'test'))

samples/a2_test_plugin/a2_test_plugin/views.py

@@ -0,0 +1,4 @@
+from django.http import HttpResponse
+
+def test(request):
+    return HttpResponse('coucou')

samples/a2_test_plugin/setup.py

@@ -0,0 +1,17 @@
+#!/usr/bin/python
+from setuptools import setup, find_packages
+import os
+
+setup(name='authentic2-test-plugin',
+        version='1.0',
+        license='AGPLv3',
+        description='Authentic2 Test Plugin',
+        author="Entr'ouvert",
+        author_email="info@entrouvert.com",
+        packages=find_packages(os.path.dirname(__file__) or '.'),
+        entry_points={
+            'authentic2.plugin': [
+                'test-plugin = a2_test_plugin:Plugin',
+            ],
+        },
+)