Merged Thomas Habets 2009-01-07 XML output for "be show".

I rewrote a few of his routines, e.g. generalizing
Comment.string_thread to run a caller-specified method avoided the
need for some duplicate code in Comment.xml_thread.  There was also a
reasonable reorganization of libbe.settings_object.versioned_property
because the <in_reply_to> field of the Comment.xml output was giving
me `-1' (= old settings_object.EMPTY) instead of None, even after I
had set comm.in_reply_to to None.  The rewritten versioned_property
avoids the ambiguity of UNPRIMED vs EMPTY, and avoids the stupididy of
my using EMPTY=-1 ;).

1 files changed, 6 insertions, 4 deletions

diff --git a/libbe/properties.py b/libbe/properties.py
index 176e898..a8e89fb 100644
--- a/libbe/properties.py
+++ b/libbe/properties.py
@@ -28,6 +28,7 @@ for more information on decorators.
 
 import unittest
 
+
 class ValueCheckError (ValueError):
     def __init__(self, name, value, allowed):
         msg = "%s not in %s for %s" % (value, allowed, name)
@@ -65,10 +66,11 @@ def doc_property(doc=None):
         return funcs
     return decorator
 
-def local_property(name):
+def local_property(name, null=None):
     """
     Define get/set access to per-parent-instance local storage.  Uses
     ._<name>_value to store the value for a particular owner instance.
+    If the ._<name>_value attribute does not exist, returns null.
     """
     def decorator(funcs):
         if hasattr(funcs, "__call__"):
@@ -78,7 +80,7 @@ def local_property(name):
         def _fget(self):
             if fget is not None:
                 fget(self)
-            value = getattr(self, "_%s_value" % name, None)
+            value = getattr(self, "_%s_value" % name, null)
             return value
         def _fset(self, value):
             setattr(self, "_%s_value" % name, value)
@@ -90,7 +92,7 @@ def local_property(name):
         return funcs
     return decorator
 
-def settings_property(name):
+def settings_property(name, null=None):
     """
     Similar to local_property, except where local_property stores the
     value in instance._<name>_value, settings_property stores the
@@ -104,7 +106,7 @@ def settings_property(name):
         def _fget(self):
             if fget is not None:
                 fget(self)
-            value = self.settings.get(name, None)
+            value = self.settings.get(name, null)
             return value
         def _fset(self, value):
             self.settings[name] = value