Fix time zone canonicalization behaviour in DateTimeFormat test

As of the Time Zone Canonicalization proposal which is stage 3, the
original time zone name should be preserved in Intl.DateTimeFormat
.prototype.resolvedOptions.

Add a separate test that uses Temporal.ZonedDateTime.prototype.equals
to test the canonicalization behaviour.

Author: ptomato

test/intl402/DateTimeFormat/canonicalize-timezone.js

@@ -56,6 +56,7 @@ info: |
       a. Let _timeZoneIdentifierRecord_ be GetAvailableNamedTimeZoneIdentifier(_timeZone_).
       b. If _timeZoneIdentifierRecord_ is ~empty~, throw a RangeError exception.
       c. Set _timeZone_ to _timeZoneIdentifierRecord_.[[PrimaryIdentifier]].
+features: [canonical-tz]
 ---*/
 
 const timeZones = [
@@ -96,7 +97,7 @@ const timeZones = [
 for (const [timeZone, expected] of timeZones) {
   assert.sameValue(
     new Intl.DateTimeFormat([], { timeZone }).resolvedOptions().timeZone,
-    expected,
-    "Time zone name " + timeZone + " should be canonicalized to " + expected
+    timeZone,
+    "Time zone name " + timeZone + " should be preserved and not canonicalized to " + expected
   );
 }

test/intl402/Temporal/ZonedDateTime/prototype/equals/canonicalize-timezone.js

@@ -0,0 +1,104 @@
+// Copyright 2025 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+/*---
+esid: sec-use-of-iana-time-zone-database
+description: >
+  Primary and non-primary time zone identifiers must correspond with IANA Time
+  Zone Database Zones and Link names, subject to explicit exceptions, and must
+  direct time zone name canonicalization.
+info: |
+    AvailableNamedTimeZoneIdentifiers ( )
+
+    1. Let _identifiers_ be a List containing the String value of each Zone or Link name in the IANA Time Zone Database.
+    2. ...
+    3. ...
+    4. Let _result_ be a new empty List.
+    5. For each element _identifier_ of _identifiers_, do
+      a. Let _primary_ be _identifier_.
+      b. If _identifier_ is a Link name in the IANA Time Zone Database and _identifier_ is not present in the “TZ” column of <code>zone.tab</code> of the IANA Time Zone Database, then
+        i. Let _zone_ be the Zone name that _identifier_ resolves to, according to the rules for resolving Link names in the IANA Time Zone Database.
+        ii. If _zone_ starts with *"Etc/"*, then
+          1. Set _primary_ to _zone_.
+        iii. Else,
+          1. Let _identifierCountryCode_ be the <a href="https://www.iso.org/glossary-for-iso-3166.html">ISO 3166-1 Alpha-2</a> country code whose territory contains the geographical area corresponding to _identifier_.
+          2. Let _zoneCountryCode_ be the ISO 3166-1 Alpha-2 country code whose territory contains the geographical area corresponding to _zone_.
+          3. If _identifierCountryCode_ is _zoneCountryCode_, then
+            a. Set _primary_ to _zone_.
+          4. Else,
+            a. Let _countryCodeLineCount_ be the number of lines in file <code>zone.tab</code> of the IANA Time Zone Database where the “country-code” column is _identifierCountryCode_.
+            b. If _countryCodeLineCount_ is 1, then
+              i. Let _countryCodeLine_ be the line in file <code>zone.tab</code> of the IANA Time Zone Database where the “country-code” column is _identifierCountryCode_.
+              ii. Set _primary_ to the contents of the “TZ” column of _countryCodeLine_.
+            c. Else,
+              i. Let _backzone_ be *undefined*.
+              ii. Let _backzoneLinkLines_ be the List of lines in the file <code>backzone</code> of the IANA Time Zone Database that start with either *"Link "* or *"#PACKRATLIST zone.tab Link "*.
+              iii. ...
+              iv. Assert: _backzone_ is not *undefined*.
+              v. Set _primary_ to _backzone_.
+      c. If _primary_ is one of *"Etc/UTC"*, *"Etc/GMT"*, or *"GMT"*, set _primary_ to *"UTC"*.
+      d. ...
+      e. Let _record_ be the Time Zone Identifier Record { [[Identifier]]: _identifier_, [[PrimaryIdentifier]]: _primary_ }.
+      f. Append _record_ to _result_.
+    6. ...
+    7. Return _result_.
+
+    GetAvailableNamedTimeZoneIdentifier ( _timeZoneIdentifier_ )
+
+    1. For each element _record_ of AvailableNamedTimeZoneIdentifiers(), do
+      a. If _record_.[[Identifier]] is an ASCII-case-insensitive match for _timeZoneIdentifier_, return record.
+    2. Return ~empty~.
+
+    CreateDateTimeFormat ( _newTarget_, _locales_, _options_, _required_, _defaults_ )
+
+    29. If IsTimeZoneOffsetString(_timeZone_) is *true*, then
+      ...
+    30. Else,
+      a. Let _timeZoneIdentifierRecord_ be GetAvailableNamedTimeZoneIdentifier(_timeZone_).
+      b. If _timeZoneIdentifierRecord_ is ~empty~, throw a RangeError exception.
+      c. Set _timeZone_ to _timeZoneIdentifierRecord_.[[PrimaryIdentifier]].
+features: [Temporal, canonical-tz]
+---*/
+
+const timeZones = [
+  // Europe/Prague is not a Link name.
+  ["Europe/Prague", "Europe/Prague"],
+
+  // `backward` identifies "Europe/Bratislava" as a Link name targeting "Europe/Prague":
+  //   Link	Europe/Prague		Europe/Bratislava
+  // Europe/Bratislava's country code "SK" has only one time zone in `zone.tab`.
+  ["Europe/Bratislava", "Europe/Bratislava"],
+
+  // `backward` identifies "Australia/Canberra" as a Link targeting "Australia/Sydney":
+  //   Link	Australia/Sydney	Australia/Canberra
+  // Both share the country code "AU".
+  ["Australia/Canberra", "Australia/Sydney"],
+
+  // `backward` identifies "Atlantic/Jan_Mayen" as a Link name targeting "Europe/Berlin":
+  //   Link	Europe/Berlin		Atlantic/Jan_Mayen
+  // Atlantic/Jan_Mayen's country code "SJ" has only one time zone in `zone.tab`.
+  ["Atlantic/Jan_Mayen", "Arctic/Longyearbyen"],
+
+  // `backward` identifies "Pacific/Truk" as a Link name targeting "Pacific/Port_Moresby":
+  //   Link	Pacific/Port_Moresby	Pacific/Truk	#= Pacific/Chuuk
+  // Pacific/Chuuk's country code "FM" has multiple time zones in `zone.tab`.
+  // `backzone` identifies "Pacific/Truk" as a Link name targeting "Pacific/Chuuk":
+  //   Link Pacific/Chuuk Pacific/Truk
+  ["Pacific/Truk", "Pacific/Chuuk"],
+
+  // `backward` identifies "Etc/UCT" as a Link name targeting "Etc/UTC":
+  //   Link	Etc/UTC			Etc/UCT
+  ["Etc/UCT", "UTC"],
+
+  // `backward` identifies "Etc/GMT0" as a Link name targeting "Etc/GMT":
+  //   Link	Etc/GMT			Etc/GMT0
+  ["Etc/GMT0", "UTC"]
+];
+
+for (const [timeZone, expected] of timeZones) {
+  const z1 = new Temporal.ZonedDateTime(0n, timeZone);
+  const z2 = new Temporal.ZonedDateTime(0n, expected);
+  assert(
+    z1.equals(z2),
+    "Time zone name " + timeZone + " should be canonicalized to " + expected
+  );
+}