Merge ~knobby/layer-snap:mwilson/is-installed into ~stub/layer-snap:master

[Mike Wilson]

[Stuart Bishop (stub)]

The idea is fine. I need the get_installed_state_name and get_disabled_state_name function names changed to match recommended nomenclature before I can land it (get_installed_flag and get_disabled_flag rather than _state_name)

My use cases just hard code the documented flag names, but I can see that the new methods will be useful when the set of snaps is configurable.

review: Needs Fixing

[Stuart Bishop (stub)]

review: Approve

diff --git a/lib/charms/layer/snap.py b/lib/charms/layer/snap.py
index 54d4cf8..acd6947 100644
--- a/lib/charms/layer/snap.py
+++ b/lib/charms/layer/snap.py
@@ -25,6 +25,14 @@ from time import sleep
 from datetime import datetime, timedelta
 
 
+def get_installed_flag(snapname):
+    return 'snap.installed.{}'.format(snapname)
+
+
+def get_disabled_flag(snapname):
+    return 'snap.disabled.{}'.format(snapname)
+
+
 def install(snapname, **kw):
     '''Install a snap.
 
@@ -36,7 +44,7 @@ def install(snapname, **kw):
     If the snap.installed.{snapname} state is already set then the refresh()
     function is called.
     '''
-    installed_state = 'snap.installed.{}'.format(snapname)
+    installed_state = get_installed_flag(snapname)
     if reactive.is_state(installed_state):
         refresh(snapname, **kw)
     else:
@@ -52,11 +60,15 @@ def install(snapname, **kw):
 
     # Installing any snap will first ensure that 'core' is installed. Set an
     # appropriate flag for consumers that want to get/set core options.
-    core_installed = 'snap.installed.core'
+    core_installed = get_installed_flag('core')
     if not reactive.is_state(core_installed):
         reactive.set_state(core_installed)
 
 
+def is_installed(snapname):
+    return reactive.is_state(get_installed_flag(snapname))
+
+
 def refresh(snapname, **kw):
     '''Update a snap.
 
@@ -86,7 +98,7 @@ def remove(snapname):
     hookenv.log('Removing snap {}'.format(snapname))
     subprocess.check_call(['snap', 'remove', snapname],
                           universal_newlines=True)
-    reactive.remove_state('snap.installed.{}'.format(snapname))
+    reactive.remove_state(get_installed_flag(snapname))
 
 
 def connect(plug, slot):
@@ -121,7 +133,7 @@ def disable(snapname):
     exist
     '''
     hookenv.log('Disabling {} snap'.format(snapname))
-    if not reactive.is_flag_set('snap.installed.{}'.format(snapname)):
+    if not reactive.is_flag_set(get_installed_flag(snapname)):
         hookenv.log(
             'Cannot disable {} snap because it is not installed'.format(
                 snapname), hookenv.WARNING)
@@ -129,7 +141,7 @@ def disable(snapname):
 
     subprocess.check_call(['snap', 'disable', snapname],
                           universal_newlines=True)
-    reactive.set_flag('snap.disabled.{}'.format(snapname))
+    reactive.set_flag(get_disabled_flag(snapname))
 
 
 def enable(snapname):
@@ -141,7 +153,7 @@ def enable(snapname):
     exist
     '''
     hookenv.log('Enabling {} snap'.format(snapname))
-    if not reactive.is_flag_set('snap.installed.{}'.format(snapname)):
+    if not reactive.is_flag_set(get_installed_flag(snapname)):
         hookenv.log(
             'Cannot enable {} snap because it is not installed'.format(
                 snapname), hookenv.WARNING)
@@ -149,7 +161,7 @@ def enable(snapname):
 
     subprocess.check_call(['snap', 'enable', snapname],
                           universal_newlines=True)
-    reactive.clear_flag('snap.disabled.{}'.format(snapname))
+    reactive.clear_flag(get_disabled_flag(snapname))
 
 
 def restart(snapname):
@@ -159,7 +171,7 @@ def restart(snapname):
     exist
     '''
     hookenv.log('Restarting {} snap'.format(snapname))
-    if not reactive.is_flag_set('snap.installed.{}'.format(snapname)):
+    if not reactive.is_flag_set(get_installed_flag(snapname)):
         hookenv.log(
             'Cannot restart {} snap because it is not installed'.format(
                 snapname), hookenv.WARNING)
@@ -175,7 +187,7 @@ def set(snapname, key, value):
     This method will fail if snapname is not an installed snap
     '''
     hookenv.log('Set config {}={} for snap {}'.format(key, value, snapname))
-    if not reactive.is_flag_set('snap.installed.{}'.format(snapname)):
+    if not reactive.is_flag_set(get_installed_flag(snapname)):
         hookenv.log(
             'Cannot set {} snap config because it is not installed'.format(
                 snapname), hookenv.WARNING)
@@ -227,7 +239,7 @@ def get(snapname, key):
     This method will fail if snapname is not an installed snap
     '''
     hookenv.log('Get config {} for snap {}'.format(key, snapname))
-    if not reactive.is_flag_set('snap.installed.{}'.format(snapname)):
+    if not reactive.is_flag_set(get_installed_flag(snapname)):
         hookenv.log(
             'Cannot get {} snap config because it is not installed'.format(
                 snapname), hookenv.WARNING)