document: fix regressions at storage and node_descriptor

Since the introduction of __len__, the descriptors were broken for the
ftp module. Fix.

bzr revid: p_christ@hol.gr-20101103112605-tu6n6529mbdc18ve

addons/document/document_storage.py

@@ -181,7 +181,8 @@ class nodefd_db(StringIO, nodes.node_descriptor):
             cr = ira_browse._cr # reuse the cursor of the browse object, just now
             cr.execute('SELECT db_datas FROM ir_attachment WHERE id = %s',(ira_browse.id,))
             data = cr.fetchone()[0]
-            self._size = len(data)
+            if data:
+                self._size = len(data)
             StringIO.__init__(self, data)
         elif mode in ('w', 'w+'):
             StringIO.__init__(self, None)
@@ -260,7 +261,8 @@ class nodefd_db64(StringIO, nodes.node_descriptor):
         
         if mode in ('r', 'r+'):
             data = base64.decodestring(ira_browse.db_datas)
-            self._size = len(data)
+            if data:
+                self._size = len(data)
             StringIO.__init__(self, data)
         elif mode in ('w', 'w+'):
             StringIO.__init__(self, None)

addons/document/nodes.py

@@ -181,6 +181,14 @@ class node_descriptor(object):
     def __len__(self):
         return self.size()
 
+    def __nonzero__(self):
+        """ Ensure that a node_descriptor will never equal False
+        
+            Since we do define __len__ and __iter__ for us, we must avoid
+            being regarded as non-true objects.
+        """
+        return True
+
     def next(self, str):
         raise NotImplementedError