Temporal: Increase coverage of dateStyle and timeStyle

Add coverage in particular for dateStyle: undefined and timeStyle:
undefined, and for dateStyle applying to PlainMonthDay/PlainYearMonth
which were not tested.

test/intl402/Temporal/Instant/prototype/toLocaleString/dateStyle-timeStyle-undefined.js

@@ -0,0 +1,18 @@
+// Copyright (C) 2025 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: dateStyle or timeStyle present but undefined
+features: [BigInt, Temporal]
+---*/
+
+const instant = new Temporal.Instant(957270896_987_650_000n);
+const defaultFormatter = new Intl.DateTimeFormat("en");
+const expected = defaultFormatter.format(instant);
+
+const actualDate = instant.toLocaleString("en", { dateStyle: undefined });
+assert.sameValue(actualDate, expected, "dateStyle undefined is the same as being absent");
+
+const actualTime = instant.toLocaleString("en", { timeStyle: undefined });
+assert.sameValue(actualTime, expected, "timeStyle undefined is the same as being absent");

test/intl402/Temporal/Instant/prototype/toLocaleString/options-conflict.js

@@ -44,4 +44,8 @@ for (const [ option, value ] of conflictingOptions) {
   assert.throws(TypeError, function() {
     instant.toLocaleString("en", { [option]: value, timeStyle: "short" });
   }, `instant.toLocaleString("en", { ${option}: "${value}",  timeStyle: "short" }) throws TypeError`);
+
+  // dateStyle or timeStyle present but undefined does not conflict
+  instant.toLocaleString("en", { [option]: value, dateStyle: undefined });
+  instant.toLocaleString("en", { [option]: value, timeStyle: undefined });
 }

test/intl402/Temporal/PlainDate/prototype/toLocaleString/dateStyle-timeStyle-undefined.js

@@ -0,0 +1,18 @@
+// Copyright (C) 2025 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: dateStyle or timeStyle present but undefined
+features: [Temporal]
+---*/
+
+const date = new Temporal.PlainDate(2000, 5, 2);
+const defaultFormatter = new Intl.DateTimeFormat("en");
+const expected = defaultFormatter.format(date);
+
+const actualDate = date.toLocaleString("en", { dateStyle: undefined });
+assert.sameValue(actualDate, expected, "dateStyle undefined is the same as being absent");
+
+const actualTime = date.toLocaleString("en", { timeStyle: undefined });
+assert.sameValue(actualTime, expected, "timeStyle undefined is the same as being absent");

test/intl402/Temporal/PlainDate/prototype/toLocaleString/options-conflict.js

@@ -30,8 +30,16 @@ const date = new Temporal.PlainDate(2000, 5, 2);
 
 assert.sameValue(typeof date.toLocaleString("en", { dateStyle: "short" }), "string");
 
+assert.throws(TypeError, function () {
+  date.toLocaleString("en", { timeStyle: "short" });
+}, "timeStyle conflicts with PlainDate");
+
 for (const [ option, value ] of conflictingOptions) {
   assert.throws(TypeError, function() {
     date.toLocaleString("en", { [option]: value, dateStyle: "short" });
   }, `date.toLocaleString("en", { ${option}: "${value}",  dateStyle: "short" }) throws TypeError`);
+
+  // dateStyle or timeStyle present but undefined does not conflict
+  date.toLocaleString("en", { [option]: value, dateStyle: undefined });
+  date.toLocaleString("en", { [option]: value, timeStyle: undefined });
 }

test/intl402/Temporal/PlainDateTime/prototype/toLocaleString/dateStyle-timeStyle-undefined.js

@@ -0,0 +1,18 @@
+// Copyright (C) 2025 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: dateStyle or timeStyle present but undefined
+features: [Temporal]
+---*/
+
+const datetime = new Temporal.PlainDateTime(2000, 5, 2, 12, 34, 56, 987, 654, 321);
+const defaultFormatter = new Intl.DateTimeFormat("en");
+const expected = defaultFormatter.format(datetime);
+
+const actualDate = datetime.toLocaleString("en", { dateStyle: undefined });
+assert.sameValue(actualDate, expected, "dateStyle undefined is the same as being absent");
+
+const actualTime = datetime.toLocaleString("en", { timeStyle: undefined });
+assert.sameValue(actualTime, expected, "timeStyle undefined is the same as being absent");

test/intl402/Temporal/PlainDateTime/prototype/toLocaleString/options-conflict.js

@@ -44,4 +44,8 @@ for (const [ option, value ] of conflictingOptions) {
   assert.throws(TypeError, function() {
     datetime.toLocaleString("en", { [option]: value, timeStyle: "short" });
   }, `datetime.toLocaleString("en", { ${option}: "${value}",  timeStyle: "short" }) throws TypeError`);
+
+  // dateStyle or timeStyle present but undefined does not conflict
+  datetime.toLocaleString("en", { [option]: value, dateStyle: undefined });
+  datetime.toLocaleString("en", { [option]: value, timeStyle: undefined });
 }

test/intl402/Temporal/PlainMonthDay/prototype/toLocaleString/dateStyle-timeStyle-undefined.js

@@ -0,0 +1,16 @@
+// Copyright (C) 2025 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: dateStyle present but undefined
+features: [Temporal]
+---*/
+
+const defaultFormatter = new Intl.DateTimeFormat("en");
+const { calendar } = defaultFormatter.resolvedOptions();
+const monthday = new Temporal.PlainMonthDay(5, 2, calendar);
+const expected = defaultFormatter.format(monthday);
+
+const actual = monthday.toLocaleString("en", { dateStyle: undefined });
+assert.sameValue(actual, expected, "dateStyle undefined is the same as being absent");

test/intl402/Temporal/PlainMonthDay/prototype/toLocaleString/dateStyle.js

@@ -29,3 +29,9 @@ assert(
   !dateIslamic.toLocaleString("en-u-ca-islamic-tbla", { dateStyle: "short" }).includes("Ramadan"),
   "dateStyle: short does not write month of Ramadan out in full"
 );
+
+const dateWithReferenceYear = new Temporal.PlainMonthDay(5, 31, "gregory", 2222);
+assert(
+  !dateWithReferenceYear.toLocaleString("en", { dateStyle: "full" }).includes("2222"),
+  "dateStyle: full should not format reference year at all"
+);

test/intl402/Temporal/PlainMonthDay/prototype/toLocaleString/options-conflict.js

@@ -0,0 +1,41 @@
+// Copyright (C) 2025 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sup-temporal.plainmonthday.prototype.tolocalestring
+description: >
+    Conflicting properties of dateStyle must be rejected with a TypeError for the options argument
+info: |
+  CreateDateTimeFormat:
+
+  45. If _dateStyle_ is not *undefined* or _timeStyle_ is not *undefined*, then
+    a. If _hasExplicitFormatComponents_ is *true*, then
+      i. Throw a *TypeError* exception.
+    b. If _required_ is ~date~ and _timeStyle_ is not *undefined*, then
+      i. Throw a *TypeError* exception.
+features: [Temporal]
+---*/
+
+const conflictingOptions = [
+  "month",
+  "day",
+];
+const calendar = new Intl.DateTimeFormat("en").resolvedOptions().calendar;
+const md = new Temporal.PlainMonthDay(4, 17, calendar);
+
+// dateStyle does not conflict with PlainMonthDay
+md.toLocaleString("en", { dateStyle: "short" });
+
+assert.throws(TypeError, function () {
+  md.toLocaleString("en", { timeStyle: "short" });
+}, "timeStyle conflicts with PlainMonthDay");
+
+for (const option of conflictingOptions) {
+  assert.throws(TypeError, function() {
+    md.toLocaleString("en", { [option]: "numeric", dateStyle: "short" });
+  }, `${option} conflicts with dateStyle`);
+
+  // dateStyle or timeStyle present but undefined does not conflict
+  md.toLocaleString("en", { [option]: "numeric", dateStyle: undefined });
+  md.toLocaleString("en", { [option]: "numeric", timeStyle: undefined });
+}

test/intl402/Temporal/PlainTime/prototype/toLocaleString/options-conflict.js

@@ -30,8 +30,16 @@ const time = new Temporal.PlainTime(12, 34, 56, 987, 654, 321);
 
 assert.sameValue(typeof time.toLocaleString("en", { timeStyle: "short" }), "string");
 
+assert.throws(TypeError, function () {
+  time.toLocaleString("en", { dateStyle: "short" });
+}, "dateStyle conflicts with PlainTime");
+
 for (const [ option, value ] of conflictingOptions) {
   assert.throws(TypeError, function() {
     time.toLocaleString("en", { [option]: value, timeStyle: "short" });
   }, `time.toLocaleString("en", { ${option}: "${value}",  timeStyle: "short" }) throws TypeError`);
+
+  // dateStyle or timeStyle present but undefined does not conflict
+  time.toLocaleString("en", { [option]: value, dateStyle: undefined });
+  time.toLocaleString("en", { [option]: value, timeStyle: undefined });
 }

test/intl402/Temporal/PlainTime/prototype/toLocaleString/timeStyle-undefined.js

@@ -0,0 +1,15 @@
+// Copyright (C) 2025 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: timeStyle present but undefined
+features: [Temporal]
+---*/
+
+const time = new Temporal.PlainTime(12, 34, 56, 987, 654, 321);
+const defaultFormatter = new Intl.DateTimeFormat("en");
+const expected = defaultFormatter.format(time);
+
+const actual = time.toLocaleString("en", { timeStyle: undefined });
+assert.sameValue(actual, expected, "timeStyle undefined is the same as being absent");

test/intl402/Temporal/PlainYearMonth/prototype/toLocaleString/dateStyle-undefined.js

@@ -0,0 +1,16 @@
+// Copyright (C) 2025 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: dateStyle present but undefined
+features: [Temporal]
+---*/
+
+const defaultFormatter = new Intl.DateTimeFormat("en");
+const { calendar } = defaultFormatter.resolvedOptions();
+const yearmonth = new Temporal.PlainYearMonth(2000, 5, calendar);
+const expected = defaultFormatter.format(yearmonth);
+
+const actual = yearmonth.toLocaleString("en", { dateStyle: undefined });
+assert.sameValue(actual, expected, "dateStyle undefined is the same as being absent");

test/intl402/Temporal/PlainYearMonth/prototype/toLocaleString/dateStyle.js

@@ -29,3 +29,9 @@ assert(
   !dateIslamic.toLocaleString("en-u-ca-islamic-tbla", { dateStyle: "short" }).includes("Ramadan"),
   "dateStyle: short does not write month of Ramadan out in full"
 );
+
+const dateWithReferenceDay = new Temporal.PlainYearMonth(2024, 5, "gregory", 31);
+assert(
+  !dateWithReferenceDay.toLocaleString("en", { dateStyle: "full" }).includes("31"),
+  "dateStyle: full should not format reference day at all"
+);

test/intl402/Temporal/PlainYearMonth/prototype/toLocaleString/options-conflict.js

@@ -0,0 +1,42 @@
+// Copyright (C) 2025 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sup-temporal.plainyearmonth.prototype.tolocalestring
+description: >
+    Conflicting properties of dateStyle must be rejected with a TypeError for the options argument
+info: |
+  CreateDateTimeFormat:
+
+  45. If _dateStyle_ is not *undefined* or _timeStyle_ is not *undefined*, then
+    a. If _hasExplicitFormatComponents_ is *true*, then
+      i. Throw a *TypeError* exception.
+    b. If _required_ is ~date~ and _timeStyle_ is not *undefined*, then
+      i. Throw a *TypeError* exception.
+features: [Temporal]
+---*/
+
+const conflictingOptions = [
+  ["era", "short"],
+  ["year", "numeric"],
+  ["month", "numeric"],
+];
+const calendar = new Intl.DateTimeFormat("en").resolvedOptions().calendar;
+const ym = new Temporal.PlainYearMonth(2024, 4, calendar);
+
+// dateStyle does not conflict with PlainYearMonth
+ym.toLocaleString("en", { dateStyle: "short" });
+
+assert.throws(TypeError, function () {
+  ym.toLocaleString("en", { timeStyle: "short" });
+}, "timeStyle conflicts with PlainYearMonth");
+
+for (const [option, value] of conflictingOptions) {
+  assert.throws(TypeError, function() {
+    ym.toLocaleString("en", { [option]: value, dateStyle: "short" });
+  }, `${option} conflicts with dateStyle`);
+
+  // dateStyle or timeStyle present but undefined does not conflict
+  ym.toLocaleString("en", { [option]: value, dateStyle: undefined });
+  ym.toLocaleString("en", { [option]: value, timeStyle: undefined });
+}

test/intl402/Temporal/ZonedDateTime/prototype/toLocaleString/dateStyle-timeStyle-undefined.js

@@ -0,0 +1,27 @@
+// Copyright (C) 2025 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.zoneddatetime.prototype.tolocalestring
+description: dateStyle or timeStyle present but undefined
+features: [BigInt, Temporal]
+---*/
+
+const datetime = new Temporal.ZonedDateTime(957270896_987_650_000n, "UTC");
+const defaultFormatter = new Intl.DateTimeFormat("en", {
+  year: "numeric",
+  month: "numeric",
+  day: "numeric",
+  hour: "numeric",
+  minute: "numeric",
+  second: "numeric",
+  timeZoneName: "short",
+  timeZone: "UTC",
+});
+const expected = defaultFormatter.format(datetime.toInstant());
+
+const actualDate = datetime.toLocaleString("en", { dateStyle: undefined });
+assert.sameValue(actualDate, expected, "dateStyle undefined is the same as being absent");
+
+const actualTime = datetime.toLocaleString("en", { timeStyle: undefined });
+assert.sameValue(actualTime, expected, "timeStyle undefined is the same as being absent");

test/intl402/Temporal/ZonedDateTime/prototype/toLocaleString/options-conflict.js

@@ -45,4 +45,8 @@ for (const [ option, value ] of conflictingOptions) {
   assert.throws(TypeError, function() {
     datetime.toLocaleString("en", { [option]: value, timeStyle: "short" });
   }, `datetime.toLocaleString("en", { ${option}: "${value}",  timeStyle: "short" }) throws TypeError`);
+
+  // dateStyle or timeStyle present but undefined does not conflict
+  datetime.toLocaleString("en", { [option]: value, dateStyle: undefined });
+  datetime.toLocaleString("en", { [option]: value, timeStyle: undefined });
 }