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timezone: Correct common_timezones dictionary.
The changes are as follows: • Fix one day offset in all western zones. • Correct CST from -64800 to -21600 and CDT from -68400 to -18000. • Disambiguate PST in favor of -28000 over +28000. • Add GMT, UTC, WET, previously excluded for being at offset 0. • Add ACDT, AEDT, AKST, MET, MSK, NST, NZDT, PKT, which the previous code did not find. • Remove numbered abbreviations -12, …, +14, which are unnecessary. • Remove MSD and PKST, which are no longer used. Hardcode the dict and verify it with a test, so that future discrepancies won’t go silently unnoticed. Signed-off-by: Anders Kaseorg <anders@zulip.com>
This commit is contained in:
Anders Kaseorg
committed by
Anders Kaseorg
Anders Kaseorg
parent
fd8504e06b
commit
4ca66e7278
@@ -50,7 +50,7 @@ from zerver.lib.mention import extract_user_group, possible_mentions, possible_u
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from zerver.lib.tex import render_tex
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from zerver.lib.thumbnail import user_uploads_or_external
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from zerver.lib.timeout import TimeoutExpired, timeout
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from zerver.lib.timezone import get_common_timezones
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from zerver.lib.timezone import common_timezones
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from zerver.lib.url_encoding import encode_stream, hash_util_encode
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from zerver.lib.url_preview import preview as link_preview
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from zerver.models import (
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@@ -1240,7 +1240,7 @@ class Timestamp(markdown.inlinepatterns.Pattern):
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time_input_string = match.group('time')
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timestamp = None
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try:
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timestamp = dateutil.parser.parse(time_input_string, tzinfos=get_common_timezones())
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timestamp = dateutil.parser.parse(time_input_string, tzinfos=common_timezones)
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except ValueError:
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try:
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timestamp = datetime.datetime.fromtimestamp(float(time_input_string))
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@@ -1,7 +1,6 @@
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import datetime
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from functools import lru_cache
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from io import TextIOWrapper
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from typing import Any, Dict, Union
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from typing import Dict
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import pytz
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@@ -21,42 +20,58 @@ def get_canonical_timezone_map() -> Dict[str, str]:
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def canonicalize_timezone(key: str) -> str:
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return get_canonical_timezone_map().get(key, key)
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# This method carefully trims a list of common timezones in the pytz
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# database and handles duplicate abbreviations in favor of the most
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# common/popular offset. The output of this can be directly passed as
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# tz_data to dateutil.parser. It takes about 25ms to run, so we want
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# to cache its results (while avoiding running it on process startup
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# since we only need it for Markdown rendering).
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@lru_cache(maxsize=None)
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def get_common_timezones() -> Dict[str, Union[int, Any]]:
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tzdata = {}
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normal = datetime.datetime(2009, 9, 1) # Any random date is fine here.
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for str in pytz.all_timezones:
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tz = pytz.timezone(str)
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timedelta = tz.utcoffset(normal)
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if not timedelta:
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continue
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offset = timedelta.seconds
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tz_name = tz.tzname(normal)
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tzdata[tz_name] = offset
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# Handle known duplicates/exceptions.
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# IST: Asia/Kolkata and Europe/Dublin.
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if tz_name == 'IST':
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tzdata[tz_name] = 19800 # Asia/Kolkata
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# CDT: America/AlmostAll and America/Havana.
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if tz_name == 'CDT':
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tzdata[tz_name] = -68400 # America/AlmostAll
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# CST America/Belize -64800
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# CST America/Costa_Rica -64800
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# CST America/El_Salvador -64800
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# CST America/Guatemala -64800
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# CST America/Managua -64800
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# CST America/Regina -64800
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# CST America/Swift_Current -64800
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# CST America/Tegucigalpa -64800
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# CST Asia/Macau 28800
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# CST Asia/Shanghai 28800
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# CST Asia/Taipei 28800
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if tz_name == 'CST':
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tzdata[tz_name] = -64800 # America/All
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return tzdata
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# Note: some of these abbreviations are fundamentally ambiguous (see
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# zerver/tests/test_timezone.py), so you should never rely on them as
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# anything more than a heuristic.
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common_timezones = {
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"SST": -39600,
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"HST": -36000,
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"AKST": -32400,
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"HDT": -32400,
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"AKDT": -28800,
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"PST": -28800,
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"MST": -25200,
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"PDT": -25200,
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"CST": -21600,
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"MDT": -21600,
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"CDT": -18000,
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"EST": -18000,
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"AST": -14400,
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"EDT": -14400,
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"NST": -12600,
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"ADT": -10800,
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"NDT": -9000,
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"GMT": 0,
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"UTC": 0,
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"WET": 0,
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"BST": +3600,
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"CET": +3600,
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"MET": +3600,
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"WAT": +3600,
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"WEST": +3600,
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"CAT": +7200,
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"CEST": +7200,
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"EET": +7200,
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"MEST": +7200,
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"SAST": +7200,
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"EAT": +10800,
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"EEST": +10800,
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"IDT": +10800,
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"MSK": +10800,
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"PKT": +18000,
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"IST": +19800,
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"WIB": +25200,
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"AWST": +28800,
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"HKT": +28800,
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"WITA": +28800,
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"JST": +32400,
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"KST": +32400,
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"WIT": +32400,
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"ACST": +34200,
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"AEST": +36000,
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"ChST": +36000,
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"ACDT": +37800,
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"AEDT": +39600,
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"NZST": +43200,
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"NZDT": +46800,
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}
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@@ -1,5 +1,10 @@
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from datetime import datetime
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import pytz
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from django.utils.timezone import now as timezone_now
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from zerver.lib.test_classes import ZulipTestCase
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from zerver.lib.timezone import canonicalize_timezone
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from zerver.lib.timezone import canonicalize_timezone, common_timezones
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class TimeZoneTest(ZulipTestCase):
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@@ -7,3 +12,40 @@ class TimeZoneTest(ZulipTestCase):
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self.assertEqual(canonicalize_timezone("America/Los_Angeles"), "America/Los_Angeles")
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self.assertEqual(canonicalize_timezone("US/Pacific"), "America/Los_Angeles")
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self.assertEqual(canonicalize_timezone("Gondor/Minas_Tirith"), "Gondor/Minas_Tirith")
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def test_common_timezones(self) -> None:
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ambiguous_abbrevs = [
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("CDT", -18000), # Central Daylight Time
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("CDT", -14400), # Cuba Daylight Time
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("CST", -21600), # Central Standard Time
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("CST", +28800), # China Standard Time
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("CST", -18000), # Cuba Standard Time
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("PST", -28800), # Pacific Standard Time
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("PST", +28800), # Phillipine Standard Time
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("IST", +19800), # India Standard Time
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("IST", +7200), # Israel Standard Time
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("IST", +3600), # Ireland Standard Time
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]
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missing = set(dict(reversed(ambiguous_abbrevs)).items()) - set(
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common_timezones.items()
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)
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assert not missing, missing
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now = timezone_now()
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dates = [datetime(now.year, 6, 21), datetime(now.year, 12, 21)]
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extra = {*common_timezones.items(), *ambiguous_abbrevs}
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for name in pytz.all_timezones:
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tz = pytz.timezone(name)
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for date in dates:
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abbrev = tz.tzname(date)
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if abbrev.startswith(("-", "+")):
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continue
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delta = tz.utcoffset(date)
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assert delta is not None
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offset = delta.total_seconds()
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assert (
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common_timezones[abbrev] == offset
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or (abbrev, offset) in ambiguous_abbrevs
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), (name, abbrev, offset)
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extra.discard((abbrev, offset))
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assert not extra, extra
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