Add ISO 8601 date constraint

Add a constraint to validate that dates are expressed in the format
described by ISO 8601.

Implements: blueprint iso8601-constraint
Change-Id: I1a7e5b75eab94dc78399347517217221c6ad475c

heat/engine/resources/iso_8601.py

@@ -0,0 +1,29 @@
+#
+#    Licensed under the Apache License, Version 2.0 (the "License"); you may
+#    not use this file except in compliance with the License. You may obtain
+#    a copy of the License at
+#
+#         http://www.apache.org/licenses/LICENSE-2.0
+#
+#    Unless required by applicable law or agreed to in writing, software
+#    distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+#    WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+#    License for the specific language governing permissions and limitations
+#    under the License.
+
+import iso8601
+
+
+class ISO8601Constraint(object):
+
+    def validate(self, value, context):
+        try:
+            iso8601.parse_date(value)
+        except Exception:
+            return False
+        else:
+            return True
+
+
+def constraint_mapping():
+    return {'iso_8601': ISO8601Constraint}

heat/tests/test_iso_8601.py

@@ -0,0 +1,40 @@
+#
+#    Licensed under the Apache License, Version 2.0 (the "License"); you may
+#    not use this file except in compliance with the License. You may obtain
+#    a copy of the License at
+#
+#         http://www.apache.org/licenses/LICENSE-2.0
+#
+#    Unless required by applicable law or agreed to in writing, software
+#    distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+#    WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+#    License for the specific language governing permissions and limitations
+#    under the License.
+
+from heat.engine.resources import iso_8601
+from heat.tests.common import HeatTestCase
+
+
+class TestISO8601Constraint(HeatTestCase):
+
+    def setUp(self):
+        super(TestISO8601Constraint, self).setUp()
+        self.constraint = iso_8601.ISO8601Constraint()
+
+    def test_validate_date_format(self):
+        date = '2050-01-01'
+        self.assertTrue(self.constraint.validate(date, None))
+
+    def test_validate_datetime_format(self):
+        self.assertTrue(self.constraint.validate('2050-01-01T23:59:59', None))
+
+    def test_validate_datetime_format_with_utc_offset(self):
+        date = '2050-01-01T23:59:59+00:00'
+        self.assertTrue(self.constraint.validate(date, None))
+
+    def test_validate_datetime_format_with_utc_offset_alternate(self):
+        date = '2050-01-01T23:59:59+0000'
+        self.assertTrue(self.constraint.validate(date, None))
+
+    def test_validate_refuses_other_formats(self):
+        self.assertFalse(self.constraint.validate('Fri 13th, 2050', None))