From d902ec66c529bd9579046a2df69bad86fafafe1a Mon Sep 17 00:00:00 2001
From: Marin Purgar <marin.purgar@gmail.com>
Date: Tue, 7 Jan 2020 02:36:52 +0100
Subject: [PATCH] Add CloudWatch Alarm TreatMissingData validator (#1536)

---
 tests/test_cloudwatch.py  | 17 +++++++++++++++++
 troposphere/cloudwatch.py | 14 +++++++++++++-
 2 files changed, 30 insertions(+), 1 deletion(-)

diff --git a/tests/test_cloudwatch.py b/tests/test_cloudwatch.py
index cc281a79d..097100527 100644
--- a/tests/test_cloudwatch.py
+++ b/tests/test_cloudwatch.py
@@ -1,4 +1,5 @@
 import unittest
+import troposphere.cloudwatch as cloudwatch
 from troposphere.cloudwatch import Dashboard
 
 
@@ -36,5 +37,21 @@ def test_dashboard(self):
             )
 
 
+class TestCloudWatchValidators(unittest.TestCase):
+    def test_validate_units(self):
+        for unit in cloudwatch.VALID_UNITS:
+            cloudwatch.validate_unit(unit)
+        for bad_unit in ['Minutes', 'Bytes/Minute', 'Bits/Hour', '']:
+            with self.assertRaisesRegexp(ValueError, "must be one of"):
+                cloudwatch.validate_unit(bad_unit)
+
+    def test_validate_treat_missing_data(self):
+        for value in cloudwatch.VALID_TREAT_MISSING_DATA_TYPES:
+            cloudwatch.validate_treat_missing_data(value)
+        for bad_value in ['exists', 'notMissing', '']:
+            with self.assertRaisesRegexp(ValueError, "must be one of"):
+                cloudwatch.validate_treat_missing_data(bad_value)
+
+
 if __name__ == '__main__':
     unittest.main()
diff --git a/troposphere/cloudwatch.py b/troposphere/cloudwatch.py
index c0d5cafe7..dc168c678 100644
--- a/troposphere/cloudwatch.py
+++ b/troposphere/cloudwatch.py
@@ -16,6 +16,9 @@
                'Kilobits/Second', 'Megabits/Second', 'Gigabits/Second',
                'Terabits/Second', 'Count/Second', 'None')
 
+VALID_TREAT_MISSING_DATA_TYPES = ('breaching', 'notBreaching', 'ignore',
+                                  'missing')
+
 
 def validate_unit(unit):
     """Validate Units"""
@@ -26,6 +29,15 @@ def validate_unit(unit):
     return unit
 
 
+def validate_treat_missing_data(value):
+    """Validate TreatMissingData"""
+
+    if value not in VALID_TREAT_MISSING_DATA_TYPES:
+        raise ValueError("Alarm TreatMissingData must be one of: %s" %
+                         ", ".join(VALID_TREAT_MISSING_DATA_TYPES))
+    return value
+
+
 class MetricDimension(AWSProperty):
     props = {
         'Name': (basestring, True),
@@ -83,7 +95,7 @@ class Alarm(AWSObject):
         'Statistic': (basestring, False),
         'Threshold': (double, False),
         'ThresholdMetricId': (basestring, False),
-        'TreatMissingData': (basestring, False),
+        'TreatMissingData': (validate_treat_missing_data, False),
         'Unit': (basestring, False),
     }