Update changelog for 0.4.0

[osm/N2VC.git] / juju / tag.py

diff --git a/juju/tag.py b/juju/tag.py
index f10c5ef..2514229 100644 (file)
--- a/juju/tag.py
+++ b/juju/tag.py
@@ -1,11 +1,11 @@
 def _prefix(prefix, s):
-    if not s.startswith(prefix):
+    if s and not s.startswith(prefix):
         return '{}{}'.format(prefix, s)
     return s
 
 
 def untag(prefix, s):
-    if s.startswith(prefix):
+    if s and s.startswith(prefix):
         return s[len(prefix):]
     return s
 
@@ -21,3 +21,11 @@ def credential(cloud, user, credential_name):
 
 def model(cloud_name):
     return _prefix('model-', cloud_name)
+
+
+def user(username):
+    return _prefix('user-', username)
+
+
+def application(app_name):
+    return _prefix('application-', app_name)