Merge lp:~hloeung/charm-helpers/principal-unit-charm into lp:charm-helpers

[Haw Loeung]

Add ability to return the name of the charm of the principal unit. For example from an nrpe subordinate related to the nagios charm, it would return 'nagios' (see https://code.launchpad.net/~hloeung/nrpe-charm/+git/nrpe-charm/+merge/330474).

Unmerged revisions

790. By Haw Loeung on 2017-09-09

Fixed principal vs. unit.

789. By Haw Loeung on 2017-09-09

Add ability to return the name of the charm of the principal unit.

=== modified file 'charmhelpers/core/hookenv.py'
--- charmhelpers/core/hookenv.py	2017-08-28 08:18:34 +0000
+++ charmhelpers/core/hookenv.py	2017-09-09 11:45:03 +0000
@@ -226,6 +226,15 @@
     return None
 
 
+def principal_unit_charm():
+    """Returns the name of the charm of the principal unit, otherwise None"""
+    unit = principal_unit()
+    if not unit:
+        return None
+    md = _metadata_unit(unit)
+    return md.pop('name', None)
+
+
 @cached
 def remote_service_name(relid=None):
     """The remote service name for a given relation-id (or the current relation)"""