Merge lp:~james-page/charm-helpers/fix_hookenv_misc into lp:charm-helpers

[James Page]

Fixup misc edge cases with relation_ids and related_units

peer and container scoped relations behave a little differently to inter
container relations in that the JSON output can return null which results
in None being returned to the caller of relation_ids and related_units.

This fix works around this by returning an empty array in these instances.

[Adam Gandelman (gandelman-a)]

review: Approve

=== modified file 'charmhelpers/core/hookenv.py'
--- charmhelpers/core/hookenv.py	2013-07-05 18:22:23 +0000
+++ charmhelpers/core/hookenv.py	2013-07-10 12:33:54 +0000
@@ -197,7 +197,7 @@
     relid_cmd_line = ['relation-ids', '--format=json']
     if reltype is not None:
         relid_cmd_line.append(reltype)
-        return json.loads(subprocess.check_output(relid_cmd_line))
+        return json.loads(subprocess.check_output(relid_cmd_line)) or []
     return []
 
 
@@ -208,7 +208,7 @@
     units_cmd_line = ['relation-list', '--format=json']
     if relid is not None:
         units_cmd_line.extend(('-r', relid))
-    return json.loads(subprocess.check_output(units_cmd_line))
+    return json.loads(subprocess.check_output(units_cmd_line)) or []
 
 
 @cached
 
=== modified file 'tests/core/test_hookenv.py'
--- tests/core/test_hookenv.py	2013-07-05 18:43:41 +0000
+++ tests/core/test_hookenv.py	2013-07-10 12:33:54 +0000
@@ -223,6 +223,20 @@
 
     @patch('subprocess.check_output')
     @patch('charmhelpers.core.hookenv.relation_type')
+    def test_gets_relation_ids_empty_array(self, relation_type, check_output):
+        ids = []
+        check_output.return_value = json.dumps(None)
+        reltype = 'foo'
+        relation_type.return_value = reltype
+
+        result = hookenv.relation_ids()
+
+        self.assertEqual(result, ids)
+        check_output.assert_called_with(['relation-ids', '--format=json',
+                                         reltype])
+
+    @patch('subprocess.check_output')
+    @patch('charmhelpers.core.hookenv.relation_type')
     def test_relation_ids_no_relation_type(self, relation_type, check_output):
         ids = [1, 2, 3]
         check_output.return_value = json.dumps(ids)
@@ -262,6 +276,20 @@
 
     @patch('subprocess.check_output')
     @patch('charmhelpers.core.hookenv.relation_id')
+    def test_gets_related_units_empty_array(self, relation_id, check_output):
+        relid = 123
+        units = []
+        relation_id.return_value = relid
+        check_output.return_value = json.dumps(None)
+
+        result = hookenv.related_units()
+
+        self.assertEqual(result, units)
+        check_output.assert_called_with(['relation-list', '--format=json',
+                                         '-r', relid])
+
+    @patch('subprocess.check_output')
+    @patch('charmhelpers.core.hookenv.relation_id')
     def test_related_units_no_relation(self, relation_id, check_output):
         units = ['foo', 'bar']
         relation_id.return_value = None