Added default implementation for new interfaces for getting user IDs

and asking for a user from a user database given an ID.  The default
implementations, in BasicUser and BasicUserFolder assume that user
names are used as IDs.

Refactored the user classes so that super and nobody aren't persistent
and don't have IDs. There is now a SimpleUser that is the same as
User, sans persistence.  There is a SpecialUser that subclasses
SimpleUser.  The special user nobody is a SpecialUser. The class Super
not subclasses SpecialUser.

lib/python/AccessControl/User.py

@@ -84,7 +84,7 @@
 ##############################################################################
 """Access control package"""
 
-__version__='$Revision: 1.101 $'[11:-2]
+__version__='$Revision: 1.102 $'[11:-2]
 
 import Globals, App.Undo, socket, regex
 from Globals import HTMLFile, MessageDialog, Persistent, PersistentMapping
@@ -102,7 +102,7 @@ from AuthEncoding import pw_validate
 ListType=type([])
 NotImplemented='NotImplemented'
 
-
+_marker=[]
 
 class BasicUser(Implicit):
     """Base class for all User objects"""
@@ -118,6 +118,14 @@ class BasicUser(Implicit):
         """Return the username of a user"""
         raise NotImplemented
 
+    def getId(self):
+        
+        """Get the ID of the user. The ID can be used, at least from
+        Python, to get the user from the user's
+        UserDatabase"""
+
+        return self.getUserName()        
+
     def _getPassword(self):
         """Return the password of the user."""
         raise NotImplemented
@@ -250,10 +258,10 @@ class BasicUser(Implicit):
     __repr__=__str__
 
 
+class SimpleUser(BasicUser):
+    """A very simple user implementation
 
-
-class User(BasicUser, Persistent):
-    """Standard User object"""
+    that doesn't make a database commitment"""
 
     def __init__(self,name,password,roles,domains):
         self.name   =name
@@ -277,8 +285,14 @@ class User(BasicUser, Persistent):
         """Return the list of domain restrictions for a user"""
         return self.domains
 
+class SpecialUser(SimpleUser):
+    """Class for special users, like super and nobody"""
+    def getId(self): pass
+
+class User(SimpleUser, Persistent):
+    """Standard User object"""
 
-class Super(User):
+class Super(SpecialUser):
     """Super user
     """
     def allowed(self,parent,roles=None):
@@ -309,7 +323,7 @@ except:
     raise 'InstallError', 'Invalid format for access file - see INSTALL.txt'
 
 
-nobody=User('Anonymous User','',('Anonymous',), [])
+nobody=SpecialUser('Anonymous User','',('Anonymous',), [])
 
 
 class BasicUserFolder(Implicit, Persistent, Navigation, Tabs, RoleManager,
@@ -356,6 +370,14 @@ class BasicUserFolder(Implicit, Persistent, Navigation, Tabs, RoleManager,
         """Return the named user object or None"""
         raise NotImplemented
 
+    def getUserById(self, id, default=_marker):
+        """Return the user corresponding to the given id.
+        """
+        try: return self.getUser(id)
+        except:
+           if default is _marker: raise
+           return default
+
     def _doAddUser(self, name, password, roles, domains):
         """Create a new user"""
         raise NotImplemented