Temporal: Add coverage for formatting each Temporal object with only one component

Adds a test for each Temporal object's toLocaleString() method, formatting
them with only one option e.g. { year: 'numeric' } and comparing it with
the corresponding output for legacy Date.

See tc39/proposal-temporal#2796.

test/intl402/Temporal/Instant/prototype/toLocaleString/lone-options-accepted.js

@@ -0,0 +1,32 @@
+// Copyright (C) 2024 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.instant.prototype.tolocalestring
+description: Each date and time component can be formatted individually
+locale: [en]
+features: [Temporal]
+---*/
+
+const epochMs = 1735213600_321;  // 2024-12-26T11:46:40.321Z
+const epochNs = BigInt(epochMs) * 1_000_000n;
+const legacyDate = new Date(epochMs);
+const instant = new Temporal.Instant(epochNs);
+
+for (const options of [
+  { "year": "numeric" },
+  { "month": "long" },
+  { "day": "numeric" },
+  { "weekday": "long" },
+  { "hour": "numeric" },
+  { "minute": "numeric" },
+  { "second": "numeric" },
+  { "fractionalSecondDigits": 3 },
+  { "dayPeriod": "short" },
+  { "timeZoneName": "short" },
+  // "era" is skipped; it implies year, month, and day in "en" locale
+]) {
+  const instantResult = instant.toLocaleString("en", options);
+  const legacyDateResult = legacyDate.toLocaleString("en", options);
+  assert.sameValue(instantResult, legacyDateResult, `Instant.toLocaleString should format lone option ${JSON.stringify(options)}`);
+}

test/intl402/Temporal/PlainDate/prototype/toLocaleString/lone-options-accepted.js

@@ -0,0 +1,25 @@
+// Copyright (C) 2024 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.plaindate.prototype.tolocalestring
+description: Each date component can be formatted individually
+locale: [en]
+features: [Temporal]
+---*/
+
+const epochMs = 1735213600_321;  // 2024-12-26T11:46:40.321Z
+const legacyDate = new Date(epochMs);
+const plainDate = new Temporal.PlainDate(2024, 12, 26);
+
+for (const options of [
+  { "year": "numeric" },
+  { "month": "long" },
+  { "day": "numeric" },
+  { "weekday": "long" },
+  // "era" is skipped; it implies year, month, and day in "en" locale
+]) {
+  const plainDateResult = plainDate.toLocaleString("en", options);
+  const legacyDateResult = legacyDate.toLocaleString("en", options);
+  assert.sameValue(plainDateResult, legacyDateResult, `Instant.toLocaleString should format lone option ${JSON.stringify(options)}`);
+}

test/intl402/Temporal/PlainDateTime/prototype/toLocaleString/lone-options-accepted.js

@@ -0,0 +1,31 @@
+// Copyright (C) 2024 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.plaindatetime.prototype.tolocalestring
+description: Each date and time component can be formatted individually
+locale: [en]
+features: [Temporal]
+---*/
+
+const epochMs = 1735213600_321;  // 2024-12-26T11:46:40.321Z
+const legacyDateLocal = new Date(epochMs);
+const legacyDate = new Date(epochMs + legacyDateLocal.getTimezoneOffset() * 60 * 1000);
+const plainDateTime = new Temporal.PlainDateTime(2024, 12, 26, 11, 46, 40, 321);
+
+for (const options of [
+  { "year": "numeric" },
+  { "month": "long" },
+  { "day": "numeric" },
+  { "weekday": "long" },
+  { "hour": "numeric" },
+  { "minute": "numeric" },
+  { "second": "numeric" },
+  { "fractionalSecondDigits": 3 },
+  { "dayPeriod": "short" },
+  // "era" is skipped; it implies year, month, and day in "en" locale
+]) {
+  const plainDateTimeResult = plainDateTime.toLocaleString("en", options);
+  const legacyDateResult = legacyDate.toLocaleString("en", options);
+  assert.sameValue(plainDateTimeResult, legacyDateResult, `PlainDateTime.toLocaleString should format lone option ${JSON.stringify(options)}`);
+}

test/intl402/Temporal/PlainMonthDay/prototype/toLocaleString/lone-options-accepted.js

@@ -0,0 +1,22 @@
+// Copyright (C) 2024 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.plainmonthday.prototype.tolocalestring
+description: Each date component can be formatted individually
+locale: [en-u-ca-iso8601]
+features: [Temporal]
+---*/
+
+const epochMs = 1735213600_321;  // 2024-12-26T11:46:40.321Z
+const legacyDate = new Date(epochMs);
+const plainMonthDay = new Temporal.PlainMonthDay(12, 26);
+
+for (const options of [
+  { "month": "long" },
+  { "day": "numeric" },
+]) {
+  const plainMonthDayResult = plainMonthDay.toLocaleString("en-u-ca-iso8601", options);
+  const legacyDateResult = legacyDate.toLocaleString("en-u-ca-iso8601", options);
+  assert.sameValue(plainMonthDayResult, legacyDateResult, `PlainMonthDay.toLocaleString should format lone option ${JSON.stringify(options)}`);
+}

test/intl402/Temporal/PlainTime/prototype/toLocaleString/lone-options-accepted.js

@@ -0,0 +1,26 @@
+// Copyright (C) 2024 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.plaintime.prototype.tolocalestring
+description: Each time component can be formatted individually
+locale: [en]
+features: [Temporal]
+---*/
+
+const epochMs = 1735213600_321;  // 2024-12-26T11:46:40.321Z
+const legacyDateLocal = new Date(epochMs);
+const legacyDate = new Date(epochMs + legacyDateLocal.getTimezoneOffset() * 60 * 1000);
+const plainTime = new Temporal.PlainTime(11, 46, 40, 321);
+
+for (const options of [
+  { "hour": "numeric" },
+  { "minute": "numeric" },
+  { "second": "numeric" },
+  { "fractionalSecondDigits": 3 },
+  { "dayPeriod": "short" },
+]) {
+  const plainTimeResult = plainTime.toLocaleString("en", options);
+  const legacyDateResult = legacyDate.toLocaleString("en", options);
+  assert.sameValue(plainTimeResult, legacyDateResult, `PlainTime.toLocaleString should format lone option ${JSON.stringify(options)}`);
+}

test/intl402/Temporal/PlainYearMonth/prototype/toLocaleString/lone-options-accepted.js

@@ -0,0 +1,23 @@
+// Copyright (C) 2024 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.plainyearmonth.prototype.tolocalestring
+description: Each date and time component can be formatted individually
+locale: [en-u-ca-iso8601]
+features: [Temporal]
+---*/
+
+const epochMs = 1735213600_321;  // 2024-12-26T11:46:40.321Z
+const legacyDate = new Date(epochMs);
+const plainYearMonth = new Temporal.PlainYearMonth(2024, 12);
+
+for (const options of [
+  { "year": "numeric" },
+  { "month": "long" },
+  // "era" is skipped; it implies year, month, and day in "en" locale
+]) {
+  const plainYearMonthResult = plainYearMonth.toLocaleString("en-u-ca-iso8601", options);
+  const legacyDateResult = legacyDate.toLocaleString("en-u-ca-iso8601", options);
+  assert.sameValue(plainYearMonthResult, legacyDateResult, `Instant.toLocaleString should format lone option ${JSON.stringify(options)}`);
+}

test/intl402/Temporal/ZonedDateTime/prototype/toLocaleString/lone-options-accepted.js

@@ -0,0 +1,32 @@
+// Copyright (C) 2024 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.instant.prototype.tolocalestring
+description: Each date and time component can be formatted individually
+locale: [en, en-u-tz-utc]
+features: [Temporal]
+---*/
+
+const epochMs = 1735213600_321;  // 2024-12-26T11:46:40.321Z
+const epochNs = BigInt(epochMs) * 1_000_000n;
+const legacyDate = new Date(epochMs);
+const zonedDateTime = new Temporal.ZonedDateTime(epochNs, "UTC");
+
+for (const options of [
+  { "year": "numeric" },
+  { "month": "long" },
+  { "day": "numeric" },
+  { "weekday": "long" },
+  { "hour": "numeric" },
+  { "minute": "numeric" },
+  { "second": "numeric" },
+  { "fractionalSecondDigits": 3 },
+  { "dayPeriod": "short" },
+  { "timeZoneName": "short" },
+  // "era" is skipped; it implies year, month, and day in "en" locale
+]) {
+  const zonedDateTimeResult = zonedDateTime.toLocaleString("en", options);
+  const legacyDateResult = legacyDate.toLocaleString("en", { ...options, timeZone: "UTC" });
+  assert.sameValue(zonedDateTimeResult, legacyDateResult, `ZonedDateTime.toLocaleString should format lone option ${JSON.stringify(options)}`);
+}