Polyfill: Implement proposal-canonical-tz Stage 3

polyfill/index.d.ts

@@ -1138,6 +1138,7 @@ export namespace Temporal {
     static from(timeZone: TimeZoneLike): Temporal.TimeZone | TimeZoneProtocol;
     constructor(timeZoneIdentifier: string);
     readonly id: string;
+    equals(timeZone: TimeZoneLike): boolean;
     getOffsetNanosecondsFor(instant: Temporal.Instant | string): number;
     getOffsetStringFor(instant: Temporal.Instant | string): string;
     getPlainDateTimeFor(instant: Temporal.Instant | string, calendar?: CalendarLike): Temporal.PlainDateTime;

polyfill/lib/ecmascript.mjs

@@ -2132,7 +2132,7 @@ export function ToTemporalTimeZoneSlotValue(temporalTimeZoneLike) {
 
     const record = GetAvailableNamedTimeZoneIdentifier(tzName);
     if (!record) throw new RangeError(`Unrecognized time zone ${tzName}`);
-    return record.primaryIdentifier;
+    return record.identifier;
   }
   if (z) return 'UTC';
   // if !tzName && !z then offset must be present
@@ -2160,7 +2160,23 @@ export function TimeZoneEquals(one, two) {
   if (one === two) return true;
   const tz1 = ToTemporalTimeZoneIdentifier(one);
   const tz2 = ToTemporalTimeZoneIdentifier(two);
-  return tz1 === tz2;
+  if (tz1 === tz2) return true;
+  const offsetMinutes1 = ParseTimeZoneIdentifier(tz1).offsetMinutes;
+  const offsetMinutes2 = ParseTimeZoneIdentifier(tz2).offsetMinutes;
+  if (offsetMinutes1 === undefined && offsetMinutes2 === undefined) {
+    // Calling GetAvailableNamedTimeZoneIdentifier is costly, so (unlike the
+    // spec) the polyfill will early-return if one of them isn't recognized. Try
+    // the second ID first because it's more likely to be unknown, because it
+    // can come from the argument of TimeZone.p.equals as opposed to the first
+    // ID which comes from the receiver.
+    const idRecord2 = GetAvailableNamedTimeZoneIdentifier(tz2);
+    if (!idRecord2) return false;
+    const idRecord1 = GetAvailableNamedTimeZoneIdentifier(tz1);
+    if (!idRecord1) return false;
+    return idRecord1.primaryIdentifier === idRecord2.primaryIdentifier;
+  } else {
+    return offsetMinutes1 === offsetMinutes2;
+  }
 }
 
 export function TemporalDateTimeToDate(dateTime) {

polyfill/lib/intl.mjs

@@ -139,7 +139,7 @@ Object.defineProperty(DateTimeFormat, 'prototype', {
 
 function resolvedOptions() {
   const resolved = this[ORIGINAL].resolvedOptions();
-  resolved.timeZone = this[TZ_CANONICAL];
+  resolved.timeZone = this[TZ_ORIGINAL];
   return resolved;
 }
 

polyfill/lib/timezone.mjs

@@ -28,7 +28,7 @@ export class TimeZone {
     } else {
       const record = ES.GetAvailableNamedTimeZoneIdentifier(stringIdentifier);
       if (!record) throw new RangeError(`Invalid time zone identifier: ${stringIdentifier}`);
-      stringIdentifier = record.primaryIdentifier;
+      stringIdentifier = record.identifier;
     }
     CreateSlots(this);
     SetSlot(this, TIMEZONE_ID, stringIdentifier);
@@ -46,6 +46,11 @@ export class TimeZone {
     if (!ES.IsTemporalTimeZone(this)) throw new TypeError('invalid receiver');
     return GetSlot(this, TIMEZONE_ID);
   }
+  equals(other) {
+    if (!ES.IsTemporalTimeZone(this)) throw new TypeError('invalid receiver');
+    const timeZoneSlotValue = ES.ToTemporalTimeZoneSlotValue(other);
+    return ES.TimeZoneEquals(this, timeZoneSlotValue);
+  }
   getOffsetNanosecondsFor(instant) {
     if (!ES.IsTemporalTimeZone(this)) throw new TypeError('invalid receiver');
     instant = ES.ToTemporalInstant(instant);

polyfill/lib/zoneddatetime.mjs

@@ -478,7 +478,7 @@ export class ZonedDateTime {
     } else {
       const record = ES.GetAvailableNamedTimeZoneIdentifier(timeZoneIdentifier);
       if (!record) throw new RangeError(`toLocaleString formats built-in time zones, not ${timeZoneIdentifier}`);
-      optionsCopy.timeZone = record.primaryIdentifier;
+      optionsCopy.timeZone = record.identifier;
     }
 
     const formatter = new DateTimeFormat(locales, optionsCopy);