LibJS: Implement Temporal.ZonedDateTime.prototype.toPlainYearMonth()

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

@@ -6,6 +6,7 @@
 
 #include <AK/TypeCasts.h>
 #include <LibJS/Runtime/GlobalObject.h>
+#include <LibJS/Runtime/Temporal/AbstractOperations.h>
 #include <LibJS/Runtime/Temporal/Calendar.h>
 #include <LibJS/Runtime/Temporal/Instant.h>
 #include <LibJS/Runtime/Temporal/PlainDate.h>
@@ -65,6 +66,7 @@ void ZonedDateTimePrototype::initialize(GlobalObject& global_object)
     define_native_function(vm.names.toPlainDate, to_plain_date, 0, attr);
     define_native_function(vm.names.toPlainTime, to_plain_time, 0, attr);
     define_native_function(vm.names.toPlainDateTime, to_plain_date_time, 0, attr);
+    define_native_function(vm.names.toPlainYearMonth, to_plain_year_month, 0, attr);
     define_native_function(vm.names.getISOFields, get_iso_fields, 0, attr);
 }
 
@@ -795,6 +797,43 @@ JS_DEFINE_NATIVE_FUNCTION(ZonedDateTimePrototype::to_plain_date_time)
     return builtin_time_zone_get_plain_date_time_for(global_object, &time_zone, *instant, zoned_date_time->calendar());
 }
 
+// 6.3.50 Temporal.ZonedDateTime.prototype.toPlainYearMonth ( ), https://tc39.es/proposal-temporal/#sec-temporal.zoneddatetime.prototype.toplainyearmonth
+JS_DEFINE_NATIVE_FUNCTION(ZonedDateTimePrototype::to_plain_year_month)
+{
+    // 1. Let zonedDateTime be the this value.
+    // 2. Perform ? RequireInternalSlot(zonedDateTime, [[InitializedTemporalZonedDateTime]]).
+    auto* zoned_date_time = typed_this(global_object);
+    if (vm.exception())
+        return {};
+
+    // 3. Let timeZone be zonedDateTime.[[TimeZone]].
+    auto& time_zone = zoned_date_time->time_zone();
+
+    // 4. Let instant be ! CreateTemporalInstant(zonedDateTime.[[Nanoseconds]]).
+    auto* instant = create_temporal_instant(global_object, zoned_date_time->nanoseconds());
+
+    // 5. Let calendar be zonedDateTime.[[Calendar]].
+    auto& calendar = zoned_date_time->calendar();
+
+    // 6. Let temporalDateTime be ? BuiltinTimeZoneGetPlainDateTimeFor(timeZone, instant, calendar).
+    auto* temporal_date_time = builtin_time_zone_get_plain_date_time_for(global_object, &time_zone, *instant, calendar);
+    if (vm.exception())
+        return {};
+
+    // 7. Let fieldNames be ? CalendarFields(calendar, « "monthCode", "year" »).
+    auto field_names = calendar_fields(global_object, calendar, { "monthCode"sv, "year"sv });
+    if (vm.exception())
+        return {};
+
+    // 8. Let fields be ? PrepareTemporalFields(temporalDateTime, fieldNames, «»).
+    auto* fields = prepare_temporal_fields(global_object, *temporal_date_time, field_names, {});
+    if (vm.exception())
+        return {};
+
+    // 9. Return ? YearMonthFromFields(calendar, fields).
+    return year_month_from_fields(global_object, calendar, *fields);
+}
+
 // 6.3.52 Temporal.ZonedDateTime.prototype.getISOFields ( ), https://tc39.es/proposal-temporal/#sec-temporal.zoneddatetime.prototype.getisofields
 JS_DEFINE_NATIVE_FUNCTION(ZonedDateTimePrototype::get_iso_fields)
 {

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

@@ -50,6 +50,7 @@ private:
     JS_DECLARE_NATIVE_FUNCTION(to_plain_date);
     JS_DECLARE_NATIVE_FUNCTION(to_plain_time);
     JS_DECLARE_NATIVE_FUNCTION(to_plain_date_time);
+    JS_DECLARE_NATIVE_FUNCTION(to_plain_year_month);
     JS_DECLARE_NATIVE_FUNCTION(get_iso_fields);
 };
 

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

@@ -0,0 +1,14 @@
+describe("correct behavior", () => {
+    test("length is 0", () => {
+        expect(Temporal.ZonedDateTime.prototype.toPlainYearMonth).toHaveLength(0);
+    });
+
+    test("basic functionality", () => {
+        const timeZone = new Temporal.TimeZone("UTC");
+        const zonedDateTime = new Temporal.ZonedDateTime(1625614921000000000n, timeZone);
+        const plainYearMonth = zonedDateTime.toPlainYearMonth();
+        expect(plainYearMonth.calendar).toBe(zonedDateTime.calendar);
+        expect(plainYearMonth.year).toBe(2021);
+        expect(plainYearMonth.month).toBe(7);
+    });
+});