Add pluggable components.

 - Adds the notion of a 'plugin'.
   - A plugin has a package path and a flag specifying whether
     it's enabled or not.

 - Adds a find_pluggable_components function similar to the
   find_components one. This one dynamically searches not only
   the mailman package but all of plugins.
   - e.g. find_pluggable_components('rules', IRule) finds
     all IRule components in mailman.rules but also in
     example_plugin.rules for plugin names example_plugin.

 - Uses the find_pluggable_components function in place of
   find_components when searching for Rules, Handlers, Chains,
   EmailCommands, and Styles.

1 files changed, 2 insertions, 8 deletions

diff --git a/src/mailman/styles/manager.py b/src/mailman/styles/manager.py
index 1ec83b2a9..1969d4484 100644
--- a/src/mailman/styles/manager.py
+++ b/src/mailman/styles/manager.py
@@ -20,7 +20,7 @@
 from mailman.interfaces.configuration import ConfigurationUpdatedEvent
 from mailman.interfaces.styles import (
     DuplicateStyleError, IStyle, IStyleManager)
-from mailman.utilities.modules import add_components
+from mailman.utilities.plugins import add_pluggable_components
 from public import public
 from zope.component import getUtility
 from zope.interface import implementer
@@ -38,13 +38,7 @@ class StyleManager:
 
     def populate(self):
         self._styles.clear()
-        # Avoid circular imports.
-        from mailman.config import config
-        # Calculate the Python import paths to search.
-        paths = filter(None, (path.strip()
-                              for path in config.styles.paths.splitlines()))
-        for path in paths:
-            add_components(path, IStyle, self._styles)
+        add_pluggable_components('styles', IStyle, self._styles)
 
     def get(self, name):
         """See `IStyleManager`."""