Add setuptools plug-in entry point for defining different database backends.

Now someone could distribute a setuptools package that provided say, a MySQL
database implementation and very easily override the stock database.  How
awesome is setuptools?

Removed MANAGERS_INIT_FUNCTION since setuptools gives us a much more standard
way of defining this plug-in entry point.  Remove other old crud from
Defaults.py.

Restructure our own 'stock' database backend to be a plugin so it's totally on
par with any other package.  The only special case is that if more than one
such entry point is defined, we filter out the 'stock' one (i.e. ours) under
the assumption that the user is overriding it.  If we still have more than one
plug-in, it's an error.

Restructure the initialization subsystem to use the plug-in, doing all the
proper assertions and what not.  The IDatabase interface defines what the
database back-end plugin must provide.  I've no doubt this will eventually
need a bit more fleshing out, but it gives all this stuff a principled hook
point instead of something ad-hoc.

1 files changed, 48 insertions, 0 deletions

diff --git a/Mailman/interfaces/database.py b/Mailman/interfaces/database.py
new file mode 100644
index 000000000..8c57ae6b3
--- /dev/null
+++ b/Mailman/interfaces/database.py
@@ -0,0 +1,48 @@
+# Copyright (C) 2007 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.
+
+"""Interfaces for database interaction.
+
+By providing an object with this interface and declaring it in a package
+setup.py file as an entry point in the 'mailman.database' group with the name
+'initializer', you can distribute entirely different database layers for
+Mailman's back end.
+"""
+
+from zope.interface import Interface, Attribute
+
+
+
+class IDatabase(Interface):
+    """Database layer interface."""
+
+    def initialize():
+        """Initialize the database layer, using whatever means necessary."""
+
+    def flush():
+        """Flush current database changes."""
+
+    # XXX Eventually we probably need to support a transaction manager
+    # interface, e.g. begin(), commit(), abort().  We will probably also need
+    # to support a shutdown() method for cleanly disconnecting from the
+    # database.sy
+
+    list_manager = Attribute(
+        """The IListManager instance provided by the database layer.""")
+
+    user_manager = Attribute(
+        """The IUserManager instance provided by the database layer.""")