Fix: timezone info occasionally removed from cron job execution time (#383)

* Expose the bug in tests

* Do not remove timezone when incrementing month in _get_next_dt

Author: iamlikeme

arq/cron.py

@@ -67,9 +67,9 @@ def _get_next_dt(dt_: datetime, options: Options) -> Optional[datetime]:  # noqa
             micro = max(dt_.microsecond - options.microsecond, 0)
             if field == 'month':
                 if dt_.month == 12:
-                    return datetime(dt_.year + 1, 1, 1)
+                    return datetime(dt_.year + 1, 1, 1, tzinfo=dt_.tzinfo)
                 else:
-                    return datetime(dt_.year, dt_.month + 1, 1)
+                    return datetime(dt_.year, dt_.month + 1, 1, tzinfo=dt_.tzinfo)
             elif field in ('day', 'weekday'):
                 return (
                     dt_

tests/test_cron.py

@@ -1,7 +1,7 @@
 import asyncio
 import logging
 import re
-from datetime import datetime, timedelta
+from datetime import datetime, timedelta, timezone
 from random import random
 
 import pytest
@@ -12,37 +12,87 @@
 from arq.constants import in_progress_key_prefix
 from arq.cron import cron, next_cron
 
+tz = timezone(offset=timedelta(hours=3))
+
 
 @pytest.mark.parametrize(
     'previous,expected,kwargs',
     [
-        (datetime(2016, 6, 1, 12, 10, 10), datetime(2016, 6, 1, 12, 10, 20, microsecond=123_456), dict(second=20)),
-        (datetime(2016, 6, 1, 12, 10, 10), datetime(2016, 6, 1, 12, 11, 0, microsecond=123_456), dict(minute=11)),
-        (datetime(2016, 6, 1, 12, 10, 10), datetime(2016, 6, 1, 12, 10, 20), dict(second=20, microsecond=0)),
-        (datetime(2016, 6, 1, 12, 10, 10), datetime(2016, 6, 1, 12, 11, 0), dict(minute=11, microsecond=0)),
         (
-            datetime(2016, 6, 1, 12, 10, 11),
-            datetime(2017, 6, 1, 12, 10, 10, microsecond=123_456),
+            datetime(2016, 6, 1, 12, 10, 10, tzinfo=tz),
+            datetime(2016, 6, 1, 12, 10, 20, microsecond=123_456, tzinfo=tz),
+            dict(second=20),
+        ),
+        (
+            datetime(2016, 6, 1, 12, 10, 10, tzinfo=tz),
+            datetime(2016, 6, 1, 12, 11, 0, microsecond=123_456, tzinfo=tz),
+            dict(minute=11),
+        ),
+        (
+            datetime(2016, 6, 1, 12, 10, 10, tzinfo=tz),
+            datetime(2016, 6, 1, 12, 10, 20, tzinfo=tz),
+            dict(second=20, microsecond=0),
+        ),
+        (
+            datetime(2016, 6, 1, 12, 10, 10, tzinfo=tz),
+            datetime(2016, 6, 1, 12, 11, 0, tzinfo=tz),
+            dict(minute=11, microsecond=0),
+        ),
+        (
+            datetime(2016, 6, 1, 12, 10, 11, tzinfo=tz),
+            datetime(2017, 6, 1, 12, 10, 10, microsecond=123_456, tzinfo=tz),
             dict(month=6, day=1, hour=12, minute=10, second=10),
         ),
         (
-            datetime(2016, 6, 1, 12, 10, 10, microsecond=1),
-            datetime(2016, 7, 1, 12, 10, 10),
+            datetime(2016, 6, 1, 12, 10, 10, microsecond=1, tzinfo=tz),
+            datetime(2016, 7, 1, 12, 10, 10, tzinfo=tz),
             dict(day=1, hour=12, minute=10, second=10, microsecond=0),
         ),
-        (datetime(2032, 1, 31, 0, 0, 0), datetime(2032, 2, 28, 0, 0, 0, microsecond=123_456), dict(day=28)),
-        (datetime(2032, 1, 1, 0, 5), datetime(2032, 1, 1, 4, 0, microsecond=123_456), dict(hour=4)),
-        (datetime(2032, 1, 1, 0, 0), datetime(2032, 1, 1, 4, 2, microsecond=123_456), dict(hour=4, minute={2, 4, 6})),
-        (datetime(2032, 1, 1, 0, 5), datetime(2032, 1, 1, 4, 2, microsecond=123_456), dict(hour=4, minute={2, 4, 6})),
-        (datetime(2032, 2, 5, 0, 0, 0), datetime(2032, 3, 31, 0, 0, 0, microsecond=123_456), dict(day=31)),
         (
-            datetime(2001, 1, 1, 0, 0, 0),  # Monday
-            datetime(2001, 1, 7, 0, 0, 0, microsecond=123_456),
+            datetime(2032, 1, 31, 0, 0, 0, tzinfo=tz),
+            datetime(2032, 2, 28, 0, 0, 0, microsecond=123_456, tzinfo=tz),
+            dict(day=28),
+        ),
+        (
+            datetime(2032, 1, 1, 0, 5, tzinfo=tz),
+            datetime(2032, 1, 1, 4, 0, microsecond=123_456, tzinfo=tz),
+            dict(hour=4),
+        ),
+        (
+            datetime(2032, 1, 1, 0, 0, tzinfo=tz),
+            datetime(2032, 1, 1, 4, 2, microsecond=123_456, tzinfo=tz),
+            dict(hour=4, minute={2, 4, 6}),
+        ),
+        (
+            datetime(2032, 1, 1, 0, 5, tzinfo=tz),
+            datetime(2032, 1, 1, 4, 2, microsecond=123_456, tzinfo=tz),
+            dict(hour=4, minute={2, 4, 6}),
+        ),
+        (
+            datetime(2032, 2, 5, 0, 0, 0, tzinfo=tz),
+            datetime(2032, 3, 31, 0, 0, 0, microsecond=123_456, tzinfo=tz),
+            dict(day=31),
+        ),
+        (
+            datetime(2001, 1, 1, 0, 0, 0, tzinfo=tz),  # Monday
+            datetime(2001, 1, 7, 0, 0, 0, microsecond=123_456, tzinfo=tz),
             dict(weekday='Sun'),  # Sunday
         ),
-        (datetime(2001, 1, 1, 0, 0, 0), datetime(2001, 1, 7, 0, 0, 0, microsecond=123_456), dict(weekday=6)),  # Sunday
-        (datetime(2001, 1, 1, 0, 0, 0), datetime(2001, 11, 7, 0, 0, 0, microsecond=123_456), dict(month=11, weekday=2)),
-        (datetime(2001, 1, 1, 0, 0, 0), datetime(2001, 1, 3, 0, 0, 0, microsecond=123_456), dict(weekday='wed')),
+        (
+            datetime(2001, 1, 1, 0, 0, 0, tzinfo=tz),
+            datetime(2001, 1, 7, 0, 0, 0, microsecond=123_456, tzinfo=tz),
+            dict(weekday=6),
+        ),  # Sunday
+        (
+            datetime(2001, 1, 1, 0, 0, 0, tzinfo=tz),
+            datetime(2001, 11, 7, 0, 0, 0, microsecond=123_456, tzinfo=tz),
+            dict(month=11, weekday=2),
+        ),
+        (
+            datetime(2001, 1, 1, 0, 0, 0, tzinfo=tz),
+            datetime(2001, 1, 3, 0, 0, 0, microsecond=123_456, tzinfo=tz),
+            dict(weekday='wed'),
+        ),
     ],
 )
 def test_next_cron(previous, expected, kwargs):