Backdrop read api should always return UTC

Consumers of backdrop will always want datetimes to be represented as
UTC. Previously they had no timezone attached, which was rather confusing
as the ISODate in mongo had a timezone.

This commit will force all datetime objects coming out of backdrop into
UTC before writing them out to JSON.

backdrop/read/api.py

@@ -12,6 +12,7 @@
 from ..core.data_set import DataSet
 from ..core.database import InvalidOperationError
 from ..core.repository import DataSetConfigRepository
+from ..core.timeutils import as_utc
 
 
 GOVUK_ENV = getenv("GOVUK_ENV", "development")
@@ -43,7 +44,7 @@ def default(self, obj):
         if isinstance(obj, ObjectId):
             return str(obj)
         if isinstance(obj, datetime.datetime):
-            return obj.isoformat()
+            return as_utc(obj).isoformat()
         return json.JSONEncoder.default(self, obj)
 app.json_encoder = JsonEncoder
 

tests/read/test_read_api_json_encoder.py

@@ -0,0 +1,28 @@
+import unittest
+import pytz
+
+from hamcrest import *
+from datetime import datetime
+from backdrop.read.api import JsonEncoder
+
+
+class TestReadAPIJSONEcoder(unittest.TestCase):
+
+    def test_with_utc_date(self):
+        obj = {'date': datetime(2014, 4, 29, 1, 0, 0, 0, pytz.utc)}
+        assert_that(
+            JsonEncoder().encode(obj),
+            is_('{"date": "2014-04-29T01:00:00+00:00"}'))
+
+    def test_with_est_date(self):
+        est = pytz.timezone('US/Eastern')
+        obj = {'date': datetime(2014, 4, 29, 1, 0, 0, 0, est)}
+        assert_that(
+            JsonEncoder().encode(obj),
+            is_('{"date": "2014-04-29T06:00:00+00:00"}'))
+
+    def test_with_no_tz_date(self):
+        obj = {'date': datetime(2014, 4, 29, 1, 0)}
+        assert_that(
+            JsonEncoder().encode(obj),
+            is_('{"date": "2014-04-29T01:00:00+00:00"}'))