Fix AmbiguousTimeError in contest calendar; (Issue #2476)

judge/models/tests/test_contest.py

@@ -1,10 +1,15 @@
+import datetime
+from collections import defaultdict
+
+import pytz
 from django.core.exceptions import ValidationError
 from django.test import SimpleTestCase, TestCase
 from django.utils import timezone
 
 from judge.models import Contest, ContestParticipation, ContestTag
 from judge.models.contest import MinValueOrNoneValidator
 from judge.models.tests.util import CommonDataMixin, create_contest, create_contest_participation, create_user
+from judge.views.contests import ContestCalendar
 
 
 class ContestTestCase(CommonDataMixin, TestCase):
@@ -1048,3 +1053,28 @@ def test_fail(self):
 
         with self.assertRaises(ValidationError):
             MinValueOrNoneValidator(100)(0)
+
+
+class ContestCalendarTestCase(SimpleTestCase):
+    def test_make_aware_ambiguous_dst(self):
+        tz = pytz.timezone('America/Havana')
+        with timezone.override(tz):
+            dt = datetime.datetime(2026, 11, 1, 0, 0, 0)
+            aware_dt = ContestCalendar._make_aware(dt)
+            self.assertTrue(timezone.is_aware(aware_dt))
+            self.assertEqual(aware_dt.tzinfo.zone, 'America/Havana')
+
+    def test_get_table_ambiguous_dst(self):
+        tz = pytz.timezone('America/Havana')
+        with timezone.override(tz):
+            for year in (2026, 2020):
+                calendar_view = ContestCalendar()
+                calendar_view.year = year
+                calendar_view.month = 11
+                calendar_view.today = datetime.date(year, 11, 1)
+                calendar_view.get_contest_data = lambda start, end: (
+                    defaultdict(list), defaultdict(list), defaultdict(list),
+                )
+                table = calendar_view.get_table()
+                self.assertEqual(len(table), 5)
+                self.assertEqual(table[0][0].date, datetime.date(year, 11, 1))

judge/views/contests.py

@@ -513,10 +513,18 @@ def get_contest_data(self, start, end):
                 ends[end_date].append(contest)
         return starts, ends, oneday
 
+    @classmethod
+    def _make_aware(cls, dt):
+        tz = timezone.get_current_timezone()
+        if hasattr(tz, 'localize'):
+            return tz.localize(dt, is_dst=False)
+        return make_aware(dt)
+
     def get_table(self):
         calendar = Calendar(self.firstweekday).monthdatescalendar(self.year, self.month)
-        starts, ends, oneday = self.get_contest_data(make_aware(datetime.datetime.combine(calendar[0][0], time.min)),
-                                                     make_aware(datetime.datetime.combine(calendar[-1][-1], time.min)))
+        start = self._make_aware(datetime.datetime.combine(calendar[0][0], time.min))
+        end = self._make_aware(datetime.datetime.combine(calendar[-1][-1], time.min))
+        starts, ends, oneday = self.get_contest_data(start, end)
         return [[ContestDay(
             date=date, is_pad=date.month != self.month,
             is_today=date == self.today, starts=starts[date], ends=ends[date], oneday=oneday[date],