LibJS: Implement Temporal.Instant.prototype.toZonedDateTimeISO()

Userland/Libraries/LibJS/Runtime/CommonPropertyNames.h

@@ -436,6 +436,7 @@ namespace JS {
     P(toUpperCase)                           \
     P(toUTCString)                           \
     P(toZonedDateTime)                       \
+    P(toZonedDateTimeISO)                    \
     P(trace)                                 \
     P(trim)                                  \
     P(trimEnd)                               \

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

@@ -49,6 +49,7 @@ void InstantPrototype::initialize(GlobalObject& global_object)
     define_native_function(vm.names.toJSON, to_json, 0, attr);
     define_native_function(vm.names.valueOf, value_of, 0, attr);
     define_native_function(vm.names.toZonedDateTime, to_zoned_date_time, 1, attr);
+    define_native_function(vm.names.toZonedDateTimeISO, to_zoned_date_time_iso, 1, attr);
 }
 
 static Instant* typed_this(GlobalObject& global_object)
@@ -568,4 +569,41 @@ JS_DEFINE_NATIVE_FUNCTION(InstantPrototype::to_zoned_date_time)
     return create_temporal_zoned_date_time(global_object, instant->nanoseconds(), *time_zone, *calendar);
 }
 
+// 8.3.18 Temporal.Instant.prototype.toZonedDateTimeISO ( item ), https://tc39.es/proposal-temporal/#sec-temporal.instant.prototype.tozoneddatetimeiso
+JS_DEFINE_NATIVE_FUNCTION(InstantPrototype::to_zoned_date_time_iso)
+{
+    auto item = vm.argument(0);
+
+    // 1. Let instant be the this value.
+    // 2. Perform ? RequireInternalSlot(instant, [[InitializedTemporalInstant]]).
+    auto* instant = typed_this(global_object);
+    if (vm.exception())
+        return {};
+
+    // 3. If Type(item) is Object, then
+    if (item.is_object()) {
+        // a. Let timeZoneProperty be ? Get(item, "timeZone").
+        auto time_zone_property = item.as_object().get(vm.names.timeZone);
+        if (vm.exception())
+            return {};
+
+        // b. If timeZoneProperty is not undefined, then
+        if (!time_zone_property.is_undefined()) {
+            // i. Set item to timeZoneProperty.
+            item = time_zone_property;
+        }
+    }
+
+    // 4. Let timeZone be ? ToTemporalTimeZone(item).
+    auto* time_zone = to_temporal_time_zone(global_object, item);
+    if (vm.exception())
+        return {};
+
+    // 5. Let calendar be ! GetISO8601Calendar().
+    auto* calendar = get_iso8601_calendar(global_object);
+
+    // 6. Return ? CreateTemporalZonedDateTime(instant.[[Nanoseconds]], timeZone, calendar).
+    return create_temporal_zoned_date_time(global_object, instant->nanoseconds(), *time_zone, *calendar);
+}
+
 }

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

@@ -34,6 +34,7 @@ private:
     JS_DECLARE_NATIVE_FUNCTION(to_json);
     JS_DECLARE_NATIVE_FUNCTION(value_of);
     JS_DECLARE_NATIVE_FUNCTION(to_zoned_date_time);
+    JS_DECLARE_NATIVE_FUNCTION(to_zoned_date_time_iso);
 };
 
 }

Userland/Libraries/LibJS/Tests/builtins/Temporal/Instant/Instant.prototype.toZonedDateTimeISO.js

@@ -0,0 +1,37 @@
+describe("correct behavior", () => {
+    test("length is 1", () => {
+        expect(Temporal.Instant.prototype.toZonedDateTimeISO).toHaveLength(1);
+    });
+
+    // TODO: Un-skip when ParseTemporalTimeZoneString is fully implemented
+    test.skip("basic functionality", () => {
+        const instant = new Temporal.Instant(1625614921123456789n);
+        const zonedDateTime = instant.toZonedDateTimeISO("UTC");
+        expect(zonedDateTime.year).toBe(2021);
+        expect(zonedDateTime.month).toBe(7);
+        expect(zonedDateTime.day).toBe(6);
+        expect(zonedDateTime.hour).toBe(23);
+        expect(zonedDateTime.minute).toBe(42);
+        expect(zonedDateTime.second).toBe(1);
+        expect(zonedDateTime.millisecond).toBe(123);
+        expect(zonedDateTime.microsecond).toBe(456);
+        expect(zonedDateTime.nanosecond).toBe(789);
+        expect(zonedDateTime.calendar.id).toBe("iso8601");
+        expect(zonedDateTime.timeZone.id).toBe("UTC");
+    });
+
+    test("custom time zone object", () => {
+        const instant = new Temporal.Instant(1625614921123456789n);
+        const timeZone = new Temporal.TimeZone("UTC");
+        const zonedDateTime = instant.toZonedDateTimeISO({ timeZone });
+        expect(zonedDateTime.timeZone).toBe(timeZone);
+    });
+});
+
+describe("errors", () => {
+    test("this value must be a Temporal.Instant object", () => {
+        expect(() => {
+            Temporal.Instant.prototype.toZonedDateTimeISO.call("foo");
+        }).toThrowWithMessage(TypeError, "Not a Temporal.Instant");
+    });
+});