1 files changed, 65 insertions, 0 deletions
diff --git a/mailman/core/plugins.py b/mailman/core/plugins.py
new file mode 100644
index 000000000..cf22ad377
--- /dev/null
+++ b/mailman/core/plugins.py
@@ -0,0 +1,65 @@
+# Copyright (C) 2007-2008 by the Free Software Foundation, Inc.
+#
+# This file is part of GNU Mailman.
+#
+# GNU Mailman 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 3 of the License, or (at your option)
+# any later version.
+#
+# GNU Mailman 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
+# GNU Mailman.  If not, see <http://www.gnu.org/licenses/>.
+
+"""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()