1 files changed, 65 insertions, 0 deletions
diff --git a/mailman/app/plugins.py b/mailman/app/plugins.py
new file mode 100644
index 000000000..471ea49a7
--- /dev/null
+++ b/mailman/app/plugins.py
@@ -0,0 +1,65 @@
+# Copyright (C) 2007-2008 by the Free Software Foundation, Inc.
+#
+# This program is free software; you can redistribute it and/or
+# modify it under the terms of the GNU General Public License
+# as published by the Free Software Foundation; either version 2
+# 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 General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program; if not, write to the Free Software
+# Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301,
+# USA.
+
+"""Get a requested plugin."""
+
+import pkg_resources
+
+
+
+def get_plugin(group):
+    """Get the named plugin.
+
+    In general, this returns exactly one plugin.  If no plugins have been
+    added to the named group, the 'stock' plugin will be used.  If more than
+    one plugin -- other than the stock one -- exists, an exception will be
+    raised.
+
+    :param group: The plugin group name.
+    :return: The loaded plugin.
+    :raises RuntimeError: If more than one plugin overrides the stock plugin
+        for the named group.
+    """
+    entry_points = list(pkg_resources.iter_entry_points(group))
+    if len(entry_points) == 0:
+        raise RuntimeError('No entry points found for group: %s' % group)
+    elif len(entry_points) == 1:
+        # Okay, this is the one to use.
+        return entry_points[0].load()
+    elif len(entry_points) == 2:
+        # Find the one /not/ named 'stock'.
+        entry_points = [ep for ep in entry_points if ep.name <> 'stock']
+        if len(entry_points) == 0:
+            raise RuntimeError('No stock plugin found for group: %s' % group)
+        elif len(entry_points) == 2:
+            raise RuntimeError('Too many stock plugins defined')
+        else:
+            raise AssertionError('Insanity')
+        return entry_points[0].load()
+    else:
+        raise RuntimeError('Too many plugins for group: %s' % group)
+
+
+
+def get_plugins(group):
+    """Get and return all plugins in the named group.
+
+    :param group: Plugin group name.
+    :return: The loaded plugin.
+    """
+    for entry_point in pkg_resources.iter_entry_points(group):
+        yield entry_point.load()