LibJS: Implement Temporal.ZonedDateTime.prototype.withTimeZone

Userland/Libraries/LibJS/Runtime/CommonPropertyNames.h

@@ -487,6 +487,7 @@ namespace JS {
     P(withCalendar)                          \
     P(withPlainDate)                         \
     P(withPlainTime)                         \
+    P(withTimeZone)                          \
     P(writable)                              \
     P(year)                                  \
     P(yearMonthFromFields)                   \

Userland/Libraries/LibJS/Runtime/Temporal/ZonedDateTimePrototype.cpp

@@ -66,6 +66,7 @@ void ZonedDateTimePrototype::initialize(GlobalObject& global_object)
     u8 attr = Attribute::Writable | Attribute::Configurable;
     define_native_function(vm.names.withPlainTime, with_plain_time, 0, attr);
     define_native_function(vm.names.withPlainDate, with_plain_date, 1, attr);
+    define_native_function(vm.names.withTimeZone, with_time_zone, 1, attr);
     define_native_function(vm.names.valueOf, value_of, 0, attr);
     define_native_function(vm.names.startOfDay, start_of_day, 0, attr);
     define_native_function(vm.names.toInstant, to_instant, 0, attr);
@@ -778,6 +779,20 @@ JS_DEFINE_NATIVE_FUNCTION(ZonedDateTimePrototype::with_plain_date)
     return MUST(create_temporal_zoned_date_time(global_object, instant->nanoseconds(), time_zone, *calendar));
 }
 
+// 6.3.33 Temporal.ZonedDateTime.prototype.withTimeZone ( timeZoneLike ), https://tc39.es/proposal-temporal/#sec-temporal.zoneddatetime.prototype.withtimezone
+JS_DEFINE_NATIVE_FUNCTION(ZonedDateTimePrototype::with_time_zone)
+{
+    // 1. Let zonedDateTime be the this value.
+    // 2. Perform ? RequireInternalSlot(zonedDateTime, [[InitializedTemporalZonedDateTime]]).
+    auto* zoned_date_time = TRY(typed_this_object(global_object));
+
+    // 3. Let timeZone be ? ToTemporalTimeZone(timeZoneLike).
+    auto* time_zone = TRY(to_temporal_time_zone(global_object, vm.argument(0)));
+
+    // 4. Return ! CreateTemporalZonedDateTime(zonedDateTime.[[Nanoseconds]], timeZone, zonedDateTime.[[Calendar]]).
+    return MUST(create_temporal_zoned_date_time(global_object, zoned_date_time->nanoseconds(), *time_zone, zoned_date_time->calendar()));
+}
+
 // 6.3.44 Temporal.ZonedDateTime.prototype.valueOf ( ), https://tc39.es/proposal-temporal/#sec-temporal.zoneddatetime.prototype.valueof
 JS_DEFINE_NATIVE_FUNCTION(ZonedDateTimePrototype::value_of)
 {

Userland/Libraries/LibJS/Runtime/Temporal/ZonedDateTimePrototype.h

@@ -51,6 +51,7 @@ private:
     JS_DECLARE_NATIVE_FUNCTION(era_year_getter);
     JS_DECLARE_NATIVE_FUNCTION(with_plain_time);
     JS_DECLARE_NATIVE_FUNCTION(with_plain_date);
+    JS_DECLARE_NATIVE_FUNCTION(with_time_zone);
     JS_DECLARE_NATIVE_FUNCTION(value_of);
     JS_DECLARE_NATIVE_FUNCTION(start_of_day);
     JS_DECLARE_NATIVE_FUNCTION(to_instant);

Userland/Libraries/LibJS/Tests/builtins/Temporal/ZonedDateTime/ZonedDateTime.prototype.withTimeZone.js

@@ -0,0 +1,44 @@
+describe("correct behavior", () => {
+    test("length is 1", () => {
+        expect(Temporal.ZonedDateTime.prototype.withTimeZone).toHaveLength(1);
+    });
+
+    test("basic functionality", () => {
+        const object = {};
+        const zonedDateTime = new Temporal.ZonedDateTime(1n, object);
+        expect(zonedDateTime.timeZone).toBe(object);
+
+        const timeZone = new Temporal.TimeZone("UTC");
+        const withTimeZoneZonedDateTime = zonedDateTime.withTimeZone(timeZone);
+        expect(withTimeZoneZonedDateTime.timeZone).toBe(timeZone);
+    });
+
+    // FIXME: Enable this when time zone string parsing is implemented.
+    test.skip("from time zone string", () => {
+        const object = {};
+        const zonedDateTime = new Temporal.ZonedDateTime(1n, object);
+        expect(zonedDateTime.timeZone).toBe(object);
+
+        const withTimeZoneZonedDateTime = zonedDateTime.withTimeZone("UTC");
+        expect(withTimeZoneZonedDateTime.timeZone).toBeInstanceOf(Temporal.TimeZone);
+        expect(withTimeZoneZonedDateTime.timeZone.id).toBe("UTC");
+    });
+});
+
+describe("errors", () => {
+    test("this value must be a Temporal.ZonedDateTime object", () => {
+        expect(() => {
+            Temporal.ZonedDateTime.prototype.withTimeZone.call("foo");
+        }).toThrowWithMessage(TypeError, "Not an object of type Temporal.ZonedDateTime");
+    });
+
+    // FIXME: Enable this when time zone string parsing is implemented.
+    test.skip("from invalid time zone string", () => {
+        const zonedDateTime = new Temporal.ZonedDateTime(1n, {});
+
+        // FIXME: Use "toThrowWithMessage" once this has an error message.
+        expect(() => {
+            zonedDateTime.withTimeZone("UTCfoobar");
+        }).toThrow(RangeError);
+    });
+});