timezone: Only look up canonical time zones from the system.

Legacy time zone aliases were removed from the Debian tzdata package
in tzdata 2023c-8.

https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=1040997

Signed-off-by: Anders Kaseorg <anders@zulip.com>

zerver/lib/email_notifications.py

@@ -29,6 +29,7 @@ from zerver.lib.queue import queue_json_publish
 from zerver.lib.send_email import FromAddress, send_future_email
 from zerver.lib.soft_deactivation import soft_reactivate_if_personal_notification
 from zerver.lib.tex import change_katex_to_raw_latex
+from zerver.lib.timezone import canonicalize_timezone
 from zerver.lib.topic import get_topic_resolution_and_bare_name
 from zerver.lib.url_encoding import (
     huddle_narrow_url,
@@ -686,7 +687,9 @@ def get_onboarding_email_schedule(user: UserProfile) -> Dict[str, timedelta]:
     user_tz = user.timezone
     if user_tz == "":
         user_tz = "UTC"
-    signup_day = user.date_joined.astimezone(zoneinfo.ZoneInfo(user_tz)).isoweekday()
+    signup_day = user.date_joined.astimezone(
+        zoneinfo.ZoneInfo(canonicalize_timezone(user_tz))
+    ).isoweekday()
 
     # General rules for scheduling welcome emails flow:
     # -Do not send emails on Saturday or Sunday

zerver/lib/validator.py

@@ -140,7 +140,7 @@ def check_long_string(var_name: str, val: object) -> str:
 def check_timezone(var_name: str, val: object) -> str:
     s = check_string(var_name, val)
     try:
-        zoneinfo.ZoneInfo(s)
+        zoneinfo.ZoneInfo(canonicalize_timezone(s))
     except (ValueError, zoneinfo.ZoneInfoNotFoundError):
         raise ValidationError(
             _("{var_name} is not a recognized time zone").format(var_name=var_name)
@@ -603,11 +603,12 @@ def to_decimal(var_name: str, s: str) -> Decimal:
 
 def to_timezone_or_empty(var_name: str, s: str) -> str:
     try:
+        s = canonicalize_timezone(s)
         zoneinfo.ZoneInfo(s)
     except (ValueError, zoneinfo.ZoneInfoNotFoundError):
         return ""
     else:
-        return canonicalize_timezone(s)
+        return s
 
 
 def to_converted_or_fallback(

zerver/signals.py

@@ -11,6 +11,7 @@ from django.utils.translation import gettext as _
 from confirmation.models import one_click_unsubscribe_link
 from zerver.lib.queue import queue_json_publish
 from zerver.lib.send_email import FromAddress
+from zerver.lib.timezone import canonicalize_timezone
 from zerver.models import UserProfile
 
 if sys.version_info < (3, 9):  # nocoverage
@@ -96,7 +97,7 @@ def email_on_new_login(sender: Any, user: UserProfile, request: Any, **kwargs: A
         user_tz = user.timezone
         if user_tz == "":
             user_tz = timezone_get_current_timezone_name()
-        local_time = timezone_now().astimezone(zoneinfo.ZoneInfo(user_tz))
+        local_time = timezone_now().astimezone(zoneinfo.ZoneInfo(canonicalize_timezone(user_tz)))
         if user.twenty_four_hour_time:
             hhmm_string = local_time.strftime("%H:%M")
         else:

zerver/tests/test_new_users.py

@@ -13,6 +13,7 @@ from zerver.actions.create_user import notify_new_user
 from zerver.actions.user_settings import do_change_user_setting
 from zerver.lib.initial_password import initial_password
 from zerver.lib.test_classes import ZulipTestCase
+from zerver.lib.timezone import canonicalize_timezone
 from zerver.models import Message, Realm, Recipient, Stream, UserProfile
 from zerver.models.realms import get_realm
 from zerver.signals import JUST_CREATED_THRESHOLD, get_device_browser, get_device_os
@@ -53,7 +54,7 @@ class SendLoginEmailTest(ZulipTestCase):
             firefox_windows = (
                 "Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:47.0) Gecko/20100101 Firefox/47.0"
             )
-            user_tz = zoneinfo.ZoneInfo(user.timezone)
+            user_tz = zoneinfo.ZoneInfo(canonicalize_timezone(user.timezone))
             mock_time = datetime(year=2018, month=1, day=1, tzinfo=timezone.utc)
             reference_time = mock_time.astimezone(user_tz).strftime("%A, %B %d, %Y at %I:%M %p %Z")
             with time_machine.travel(mock_time, tick=False):