Index: acct_mgr/api.py
===================================================================
--- acct_mgr/api.py	(revision 107)
+++ acct_mgr/api.py	(working copy)
@@ -9,10 +9,6 @@
 #
 # Author: Matthew Good <trac@matt-good.net>
 
-from __future__ import generators
-
-import inspect
-
 from trac.core import *
 
 class IPasswordStore(Interface):
@@ -37,12 +33,30 @@
     def set_password(self, user, password):
         """Sets the password for the user.  This should create the user account
         if it doesn't already exist.
+        Returns True if a new account was created, False if an existing account
+        was updated.
         """
 
     def delete_user(self, user):
         """Deletes the user account.
         """
 
+class IAccountChangeListener(Interface):
+    """An interface for receiving account change events.
+    """
+
+    def user_added(self, user, password):
+        """New user
+        """
+
+    def user_password_changed(self, user, password):
+        """Password change
+        """
+
+    def user_deleted(self, user):
+        """User delete requested.
+        """
+
 class AccountManager(Component):
     """The AccountManager component handles all user account management methods
     provided by the IPasswordStore interface.
@@ -53,32 +67,33 @@
     """
 
     stores = ExtensionPoint(IPasswordStore)
+    change_listeners = ExtensionPoint(IAccountChangeListener)
 
-    def _dispatch(self, func):
-        return getattr(self._get_store(), func)
+    def get_users(self):
+        return self.password_store.get_users()
 
-    def _get_store(self):
+    def has_user(self, user):
+        return self.password_store.has_user(user)
+
+    def set_password(self, user, password):
+        if self.password_store.set_password(user, password):
+            for l in self.change_listeners:
+                l.user_created(user, password)
+        else:
+            for l in self.change_listeners:
+                l.user_password_changed(user, password)
+
+    def delete_user(self, user):
+        self.password_store.delete_user(user)
+        for l in self.change_listeners:
+            l.user_deleted(user, password)
+
+    def password_store(self):
         fmt = self.config.get('account-manager', 'password_format')
         for store in self.stores:
             if store.config_key() == fmt:
                 return store
         raise TracError('No password store found.  Please configure '
                         '"account-manager.password_format" in trac.ini.')
+    password_store = property(password_store)
 
-
-class DispatchProperty(object):
-    def __init__(self, name, fget):
-        self.name = name
-        self.fget = fget
-
-    def __get__(self, obj, objtype=None):
-        if obj is None:
-            return self
-        return self.fget(obj, self.name)
-
-# Add the IPasswordStore methods to the AccountManager to dispatch to the
-# active implementation
-for func, v in inspect.getmembers(IPasswordStore, inspect.ismethod):
-    setattr(AccountManager, func, DispatchProperty(func, AccountManager._dispatch))
-
-
Index: acct_mgr/htfile.py
===================================================================
--- acct_mgr/htfile.py	(revision 107)
+++ acct_mgr/htfile.py	(working copy)
@@ -46,7 +46,8 @@
         return self._get_users(self._get_filename())
 
     def set_password(self, user, password):
-        self._update_file(self.prefix(user), self.userline(user, password))
+        return self._update_file(self.prefix(user),
+                                 self.userline(user, password))
 
     def delete_user(self, user):
         self._update_file(self.prefix(user), None)
@@ -55,19 +56,23 @@
         return self.config.get('account-manager', 'password_file')
 
     def _update_file(self, prefix, userline):
+        if not userline:
+            raise Exception
         filename = self._get_filename()
         written = False
         if os.path.exists(filename):
             for line in fileinput.input(filename, inplace=True):
                 if not line.startswith(prefix):
                     print line,
-                elif not written and userline:
+                elif not written:
                     print userline
                     written = True
-        if not written and userline:
-            f = open(filename, 'a')
-            print >>f, userline
-            f.close()
+        if written:
+            return False # we updated an existing account
+        f = open(filename, 'a')
+        print >>f, userline
+        f.close()
+        return True # we appended a new user account
 
 
 def salt():