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LibJS: Implement time zone identifier AOs centrally within Date

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This is an editorial change in the ECMA-262 spec. See:
73926a5

The idea here is to reduce duplication of these AOs between ECMA-262,
ECMA-402, and Temporal. This patch contains only the ECMA-262 changes.
This commit is contained in:
Timothy Flynn 2023-10-03 12:14:59 -04:00 • committed by Andreas Kling
parent 0bc401a1d6
commit f31540e419
5 changed files with 88 additions and 33 deletions
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90
Userland/Libraries/LibJS/Runtime/Date.cpp
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@ -411,9 +411,57 @@ i64 get_named_time_zone_offset_nanoseconds(StringView time_zone_identifier, Cryp
return offset->seconds * 1'000'000'000;
}
// 21.4.1.24 DefaultTimeZone ( ), https://tc39.es/ecma262/#sec-defaulttimezone
// 21.4.1.23 AvailableNamedTimeZoneIdentifiers ( ), https://tc39.es/ecma262/#sec-time-zone-identifier-record
Vector<TimeZoneIdentifier> available_named_time_zone_identifiers()
{
// 1. If the implementation does not include local political rules for any time zones, then
// a. Return « the Time Zone Identifier Record { [[Identifier]]: "UTC", [[PrimaryIdentifier]]: "UTC" } ».
// NOTE: This step is not applicable as LibTimeZone will always return at least UTC, even if the TZDB is disabled.
// 2. Let identifiers be the List of unique available named time zone identifiers.
auto identifiers = TimeZone::all_time_zones();
// 3. Sort identifiers into the same order as if an Array of the same values had been sorted using %Array.prototype.sort% with undefined as comparefn.
// NOTE: LibTimeZone provides the identifiers already sorted.
// 4. Let result be a new empty List.
Vector<TimeZoneIdentifier> result;
result.ensure_capacity(identifiers.size());
bool found_utc = false;
// 5. For each element identifier of identifiers, do
for (auto identifier : identifiers) {
// a. Let primary be identifier.
auto primary = identifier.name;
// b. If identifier is a non-primary time zone identifier in this implementation and identifier is not "UTC", then
if (identifier.is_link == TimeZone::IsLink::Yes && identifier.name != "UTC"sv) {
// i. Set primary to the primary time zone identifier associated with identifier.
// ii. NOTE: An implementation may need to resolve identifier iteratively to obtain the primary time zone identifier.
primary = TimeZone::canonicalize_time_zone(identifier.name).value();
}
// c. Let record be the Time Zone Identifier Record { [[Identifier]]: identifier, [[PrimaryIdentifier]]: primary }.
TimeZoneIdentifier record { .identifier = identifier.name, .primary_identifier = primary };
// d. Append record to result.
result.unchecked_append(record);
if (!found_utc && identifier.name == "UTC"sv && primary == "UTC"sv)
found_utc = true;
}
// 6. Assert: result contains a Time Zone Identifier Record r such that r.[[Identifier]] is "UTC" and r.[[PrimaryIdentifier]] is "UTC".
VERIFY(found_utc);
// 7. Return result.
return result;
}
// 21.4.1.24 SystemTimeZoneIdentifier ( ), https://tc39.es/ecma262/#sec-systemtimezoneidentifier
// 6.4.3 DefaultTimeZone ( ), https://tc39.es/ecma402/#sup-defaulttimezone
StringView default_time_zone()
StringView system_time_zone_identifier()
{
return TimeZone::current_time_zone();
}
@ -421,21 +469,21 @@ StringView default_time_zone()
// 21.4.1.25 LocalTime ( t ), https://tc39.es/ecma262/#sec-localtime
double local_time(double time)
{
// 1. Let localTimeZone be DefaultTimeZone().
auto local_time_zone = default_time_zone();
// 1. Let systemTimeZoneIdentifier be SystemTimeZoneIdentifier().
auto system_time_zone_identifier = JS::system_time_zone_identifier();
double offset_nanoseconds { 0 };
// 2. If IsTimeZoneOffsetString(localTimeZone) is true, then
if (is_time_zone_offset_string(local_time_zone)) {
// a. Let offsetNs be ParseTimeZoneOffsetString(localTimeZone).
offset_nanoseconds = parse_time_zone_offset_string(local_time_zone);
// 2. If IsTimeZoneOffsetString(systemTimeZoneIdentifier) is true, then
if (is_time_zone_offset_string(system_time_zone_identifier)) {
// a. Let offsetNs be ParseTimeZoneOffsetString(systemTimeZoneIdentifier).
offset_nanoseconds = parse_time_zone_offset_string(system_time_zone_identifier);
}
// 3. Else,
else {
// a. Let offsetNs be GetNamedTimeZoneOffsetNanoseconds(localTimeZone, ℤ(ℝ(t) × 10^6)).
// a. Let offsetNs be GetNamedTimeZoneOffsetNanoseconds(systemTimeZoneIdentifier, ℤ(ℝ(t) × 10^6)).
auto time_bigint = Crypto::SignedBigInteger { time }.multiplied_by(s_one_million_bigint);
offset_nanoseconds = get_named_time_zone_offset_nanoseconds(local_time_zone, time_bigint);
offset_nanoseconds = get_named_time_zone_offset_nanoseconds(system_time_zone_identifier, time_bigint);
}
// 4. Let offsetMs be truncate(offsetNs / 10^6).
@ -448,20 +496,20 @@ double local_time(double time)
// 21.4.1.26 UTC ( t ), https://tc39.es/ecma262/#sec-utc-t
double utc_time(double time)
{
// 1. Let localTimeZone be DefaultTimeZone().
auto local_time_zone = default_time_zone();
// 1. Let systemTimeZoneIdentifier be SystemTimeZoneIdentifier().
auto system_time_zone_identifier = JS::system_time_zone_identifier();
double offset_nanoseconds { 0 };
// 2. If IsTimeZoneOffsetString(localTimeZone) is true, then
if (is_time_zone_offset_string(local_time_zone)) {
// a. Let offsetNs be ParseTimeZoneOffsetString(localTimeZone).
offset_nanoseconds = parse_time_zone_offset_string(local_time_zone);
// 2. If IsTimeZoneOffsetString(systemTimeZoneIdentifier) is true, then
if (is_time_zone_offset_string(system_time_zone_identifier)) {
// a. Let offsetNs be ParseTimeZoneOffsetString(systemTimeZoneIdentifier).
offset_nanoseconds = parse_time_zone_offset_string(system_time_zone_identifier);
}
// 3. Else,
else {
// a. Let possibleInstants be GetNamedTimeZoneEpochNanoseconds(localTimeZone, ℝ(YearFromTime(t)), ℝ(MonthFromTime(t)) + 1, ℝ(DateFromTime(t)), ℝ(HourFromTime(t)), ℝ(MinFromTime(t)), ℝ(SecFromTime(t)), ℝ(msFromTime(t)), 0, 0).
auto possible_instants = get_named_time_zone_epoch_nanoseconds(local_time_zone, year_from_time(time), month_from_time(time) + 1, date_from_time(time), hour_from_time(time), min_from_time(time), sec_from_time(time), ms_from_time(time), 0, 0);
// a. Let possibleInstants be GetNamedTimeZoneEpochNanoseconds(systemTimeZoneIdentifier, ℝ(YearFromTime(t)), ℝ(MonthFromTime(t)) + 1, ℝ(DateFromTime(t)), ℝ(HourFromTime(t)), ℝ(MinFromTime(t)), ℝ(SecFromTime(t)), ℝ(msFromTime(t)), 0, 0).
auto possible_instants = get_named_time_zone_epoch_nanoseconds(system_time_zone_identifier, year_from_time(time), month_from_time(time) + 1, date_from_time(time), hour_from_time(time), min_from_time(time), sec_from_time(time), ms_from_time(time), 0, 0);
// b. NOTE: The following steps ensure that when t represents local time repeating multiple times at a negative time zone transition (e.g. when the daylight saving time ends or the time zone offset is decreased due to a time zone rule change) or skipped local time at a positive time zone transition (e.g. when the daylight saving time starts or the time zone offset is increased due to a time zone rule change), t is interpreted using the time zone offset before the transition.
Crypto::SignedBigInteger disambiguated_instant;
@ -474,7 +522,7 @@ double utc_time(double time)
// d. Else,
else {
// i. NOTE: t represents a local time skipped at a positive time zone transition (e.g. due to daylight saving time starting or a time zone rule change increasing the UTC offset).
// ii. Let possibleInstantsBefore be GetNamedTimeZoneEpochNanoseconds(localTimeZone, ℝ(YearFromTime(tBefore)), ℝ(MonthFromTime(tBefore)) + 1, ℝ(DateFromTime(tBefore)), ℝ(HourFromTime(tBefore)), ℝ(MinFromTime(tBefore)), ℝ(SecFromTime(tBefore)), ℝ(msFromTime(tBefore)), 0, 0), where tBefore is the largest integral Number < t for which possibleInstantsBefore is not empty (i.e., tBefore represents the last local time before the transition).
// ii. Let possibleInstantsBefore be GetNamedTimeZoneEpochNanoseconds(systemTimeZoneIdentifier, ℝ(YearFromTime(tBefore)), ℝ(MonthFromTime(tBefore)) + 1, ℝ(DateFromTime(tBefore)), ℝ(HourFromTime(tBefore)), ℝ(MinFromTime(tBefore)), ℝ(SecFromTime(tBefore)), ℝ(msFromTime(tBefore)), 0, 0), where tBefore is the largest integral Number < t for which possibleInstantsBefore is not empty (i.e., tBefore represents the last local time before the transition).
// iii. Let disambiguatedInstant be the last element of possibleInstantsBefore.
// FIXME: This branch currently cannot be reached with our implementation, because LibTimeZone does not handle skipped time points.
@ -482,8 +530,8 @@ double utc_time(double time)
VERIFY_NOT_REACHED();
}
// e. Let offsetNs be GetNamedTimeZoneOffsetNanoseconds(localTimeZone, disambiguatedInstant).
offset_nanoseconds = get_named_time_zone_offset_nanoseconds(local_time_zone, disambiguated_instant);
// e. Let offsetNs be GetNamedTimeZoneOffsetNanoseconds(systemTimeZoneIdentifier, disambiguatedInstant).
offset_nanoseconds = get_named_time_zone_offset_nanoseconds(system_time_zone_identifier, disambiguated_instant);
}
// 4. Let offsetMs be truncate(offsetNs / 10^6).