Support for Django App Plugins

openedx/core/lib/plugins.py

@@ -1,45 +1,46 @@
 """
-Adds support for first class features that can be added to the edX platform.
+Adds support for first class plugins that can be added to the edX platform.
 """
+from collections import OrderedDict
 
 from stevedore.extension import ExtensionManager
+from openedx.core.lib.cache_utils import memoized
 
 
 class PluginError(Exception):
     """
-    Base Exception for when an error was found regarding features.
+    Base Exception for when an error was found regarding plugins.
     """
     pass
 
 
 class PluginManager(object):
     """
-    Base class that manages plugins to the edX platform.
+    Base class that manages plugins for the edX platform.
     """
     @classmethod
-    def get_available_plugins(cls):
+    @memoized
+    def get_available_plugins(cls, namespace=None):
         """
         Returns a dict of all the plugins that have been made available through the platform.
         """
         # Note: we're creating the extension manager lazily to ensure that the Python path
         # has been correctly set up. Trying to create this statically will fail, unfortunately.
-        if not hasattr(cls, "_plugins"):
-            plugins = {}
-            extension_manager = ExtensionManager(namespace=cls.NAMESPACE)  # pylint: disable=no-member
-            for plugin_name in extension_manager.names():
-                plugins[plugin_name] = extension_manager[plugin_name].plugin
-            cls._plugins = plugins
-        return cls._plugins
+        plugins = OrderedDict()
+        extension_manager = ExtensionManager(namespace=namespace or cls.NAMESPACE)  # pylint: disable=no-member
+        for plugin_name in extension_manager.names():
+            plugins[plugin_name] = extension_manager[plugin_name].plugin
+        return plugins
 
     @classmethod
-    def get_plugin(cls, name):
+    def get_plugin(cls, name, namespace=None):
         """
         Returns the plugin with the given name.
         """
-        plugins = cls.get_available_plugins()
+        plugins = cls.get_available_plugins(namespace)
         if name not in plugins:
             raise PluginError("No such plugin {name} for entry point {namespace}".format(
                 name=name,
-                namespace=cls.NAMESPACE  # pylint: disable=no-member
+                namespace=namespace or cls.NAMESPACE,  # pylint: disable=no-member
             ))
         return plugins[name]