Tidy & add test

Author: MetRonnie

cylc/flow/wallclock.py

@@ -45,8 +45,6 @@
 TIME_ZONE_STRING_UTC = "Z"
 TIME_ZONE_UTC_UTC_OFFSET = (0, 0)
 TIME_ZONE_LOCAL_UTC_OFFSET = get_local_time_zone()
-TIME_ZONE_LOCAL_UTC_OFFSET_HOURS = TIME_ZONE_LOCAL_UTC_OFFSET[0]
-TIME_ZONE_LOCAL_UTC_OFFSET_MINUTES = TIME_ZONE_LOCAL_UTC_OFFSET[1]
 
 TIME_ZONE_LOCAL_INFO = {
     "hours": TIME_ZONE_LOCAL_UTC_OFFSET[0],
@@ -151,8 +149,7 @@ def get_time_string(date_time, display_sub_seconds=False,
         else:
             custom_string = custom_time_zone_info["string_extended"]
         if date_time_is_local:
-            date_time_hours = TIME_ZONE_LOCAL_UTC_OFFSET_HOURS
-            date_time_minutes = TIME_ZONE_LOCAL_UTC_OFFSET_MINUTES
+            date_time_hours, date_time_minutes = TIME_ZONE_LOCAL_UTC_OFFSET
         else:
             date_time_hours, date_time_minutes = (0, 0)
         diff_hours = custom_hours - date_time_hours
@@ -163,18 +160,15 @@ def get_time_string(date_time, display_sub_seconds=False,
     elif override_use_utc or (override_use_utc is None and _FLAGS['utc_mode']):
         time_zone_string = TIME_ZONE_STRING_UTC
         if date_time_is_local:
-            date_time = date_time - timedelta(
-                hours=TIME_ZONE_LOCAL_UTC_OFFSET_HOURS,
-                minutes=TIME_ZONE_LOCAL_UTC_OFFSET_MINUTES
-            )
+            h, m = TIME_ZONE_LOCAL_UTC_OFFSET
+            date_time = date_time - timedelta(hours=h, minutes=m)
     else:
         if use_basic_format:
             time_zone_string = TIME_ZONE_STRING_LOCAL_BASIC
         else:
             time_zone_string = TIME_ZONE_STRING_LOCAL_EXTENDED
         if not date_time_is_local:
-            diff_hours = TIME_ZONE_LOCAL_UTC_OFFSET_HOURS
-            diff_minutes = TIME_ZONE_LOCAL_UTC_OFFSET_MINUTES
+            diff_hours, diff_minutes = TIME_ZONE_LOCAL_UTC_OFFSET
             date_time = date_time + timedelta(
                 hours=diff_hours, minutes=diff_minutes)
     if use_basic_format:

tests/unit/test_wallclock.py

@@ -14,10 +14,19 @@
 # You should have received a copy of the GNU General Public License
 # along with this program.  If not, see <http://www.gnu.org/licenses/>.
 
-import pytest
+from datetime import (
+    datetime,
+    timedelta,
+    timezone,
+)
 
 from metomi.isodatetime.data import CALENDAR
-from cylc.flow.wallclock import get_unix_time_from_time_string
+import pytest
+
+from cylc.flow.wallclock import (
+    get_time_string,
+    get_unix_time_from_time_string,
+)
 
 
 @pytest.mark.parametrize(
@@ -60,3 +69,27 @@ def test_get_unix_time_from_time_string_360(time_str, time_sec):
 def test_get_unix_time_from_time_string_error(value, error):
     with pytest.raises(error):
         get_unix_time_from_time_string(value)
+
+
+@pytest.mark.parametrize('tz_info', [
+    pytest.param(None, id="naive"),
+    pytest.param(timezone.utc, id="utc-tz-aware"),
+    pytest.param(timezone(timedelta(hours=5)), id="custom-tz-aware"),
+])
+def test_get_time_string_tzinfo(tz_info, monkeypatch: pytest.MonkeyPatch):
+    """Basic check it handles naive and timezone-aware datetime objects.
+
+    Currently we just ignore the timezone information in the datetime object.
+    """
+    # Mock UTC time zone:
+    monkeypatch.setattr(
+        'cylc.flow.wallclock.TIME_ZONE_LOCAL_UTC_OFFSET', (0, 0)
+    )
+    for fmt in ('BASIC', 'EXTENDED'):
+        monkeypatch.setattr(
+            f'cylc.flow.wallclock.TIME_ZONE_STRING_LOCAL_{fmt}', 'Z'
+        )
+
+    assert get_time_string(
+        datetime(2077, 2, 8, 13, 42, 39, 123456, tz_info)
+    ) == '2077-02-08T13:42:39Z'