Fix default template for AWS::CloudWatch::Alarm with Ceilometer

Existing template assumes certain parameters to be delimited
strings rather than lists and uses 'Fn::Split' to convert them
to list. However, delimitedstring representations of parameters
are by default converted to list for CommaDelimitedList types.
Also includes change for CommaDelimitedList to accept empty string.

Change-Id: Ib566f1d098c575a80c4f1a975eaaaac93d70af34
Closes-Bug: #1316842

etc/heat/templates/AWS_CloudWatch_Alarm.yaml

@@ -73,14 +73,14 @@ Resources:
       threshold:
         Ref: Threshold
       alarm_actions:
-        "Fn::Split": [",", {Ref: AlarmActions}]
+        Ref: AlarmActions
       ok_actions:
-        "Fn::Split": [",", {Ref: OKActions}]
+        Ref: OKActions
       insufficient_data_actions:
-        "Fn::Split": [",", {Ref: InsufficientDataActions}]
+        Ref: InsufficientDataActions
       statistic:
         "Fn::FindInMap": [StatisticMap, {Ref: Statistic}, Ceilometer]
       comparison_operator:
         "Fn::FindInMap": [ComparisonOperatorMap, {Ref: ComparisonOperator}, Ceilometer]
       matching_metadata:
-        "Fn::MemberListToMap": [Name, Value, {"Fn::Split": [",", {Ref: Dimensions}]}]
+        "Fn::MemberListToMap": [Name, Value, {Ref: Dimensions}]

heat/engine/parameters.py

@@ -316,9 +316,8 @@ class CommaDelimitedListParam(Parameter, collections.Sequence):
         # only parse when value is not already a list
         if isinstance(value, list):
             return value
-
         try:
-            if value:
+            if value is not None:
                 return value.split(',')
         except (KeyError, AttributeError) as err:
             message = _('Value must be a comma-delimited list string: %s')

heat/tests/test_parameters.py

@@ -224,6 +224,12 @@ class ParameterTest(testtools.TestCase):
                                 self.new_parameter, 'p', schema, '2')
         self.assertIn('wibble', str(err))
 
+    def test_list_value_list_default_empty(self):
+        schema = {'Type': 'CommaDelimitedList'}
+        schema['Default'] = ''
+        p = self.new_parameter('p', schema)
+        self.assertEqual([''], p.value())
+
     def test_list_value_list_good(self):
         schema = {'Type': 'CommaDelimitedList',
                   'AllowedValues': ['foo', 'bar', 'baz']}