LibJS: Implement Temporal.ZonedDateTime.prototype.monthsInYear

3 files changed, 44 insertions, 0 deletions

diff --git a/Userland/Libraries/LibJS/Runtime/Temporal/ZonedDateTimePrototype.cpp b/Userland/Libraries/LibJS/Runtime/Temporal/ZonedDateTimePrototype.cpp
index 0a31900b45..b0f8df0505 100644
--- a/Userland/Libraries/LibJS/Runtime/Temporal/ZonedDateTimePrototype.cpp
+++ b/Userland/Libraries/LibJS/Runtime/Temporal/ZonedDateTimePrototype.cpp
@@ -52,6 +52,7 @@ void ZonedDateTimePrototype::initialize(GlobalObject& global_object)
     define_native_accessor(vm.names.daysInWeek, days_in_week_getter, {}, Attribute::Configurable);
     define_native_accessor(vm.names.daysInMonth, days_in_month_getter, {}, Attribute::Configurable);
     define_native_accessor(vm.names.daysInYear, days_in_year_getter, {}, Attribute::Configurable);
+    define_native_accessor(vm.names.monthsInYear, months_in_year_getter, {}, Attribute::Configurable);
 }
 
 static ZonedDateTime* typed_this(GlobalObject& global_object)
@@ -595,4 +596,31 @@ JS_DEFINE_NATIVE_FUNCTION(ZonedDateTimePrototype::days_in_year_getter)
     return calendar_days_in_year(global_object, calendar, *temporal_date_time);
 }
 
+// 6.3.26 get Temporal.ZonedDateTime.prototype.monthsInYear, https://tc39.es/proposal-temporal/#sec-get-temporal.zoneddatetime.prototype.monthsinyear
+JS_DEFINE_NATIVE_FUNCTION(ZonedDateTimePrototype::months_in_year_getter)
+{
+    // 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. Return ? CalendarMonthsInYear(calendar, temporalDateTime).
+    return calendar_months_in_year(global_object, calendar, *temporal_date_time);
+}
+
 }
diff --git a/Userland/Libraries/LibJS/Runtime/Temporal/ZonedDateTimePrototype.h b/Userland/Libraries/LibJS/Runtime/Temporal/ZonedDateTimePrototype.h
index a646238c8e..f6663695eb 100644
--- a/Userland/Libraries/LibJS/Runtime/Temporal/ZonedDateTimePrototype.h
+++ b/Userland/Libraries/LibJS/Runtime/Temporal/ZonedDateTimePrototype.h
@@ -41,6 +41,7 @@ private:
     JS_DECLARE_NATIVE_FUNCTION(days_in_week_getter);
     JS_DECLARE_NATIVE_FUNCTION(days_in_month_getter);
     JS_DECLARE_NATIVE_FUNCTION(days_in_year_getter);
+    JS_DECLARE_NATIVE_FUNCTION(months_in_year_getter);
 };
 
 }
diff --git a/Userland/Libraries/LibJS/Tests/builtins/Temporal/ZonedDateTime/ZonedDateTime.prototype.monthsInYear.js b/Userland/Libraries/LibJS/Tests/builtins/Temporal/ZonedDateTime/ZonedDateTime.prototype.monthsInYear.js
new file mode 100644
index 0000000000..e40dad1ad4
--- /dev/null
+++ b/Userland/Libraries/LibJS/Tests/builtins/Temporal/ZonedDateTime/ZonedDateTime.prototype.monthsInYear.js
@@ -0,0 +1,15 @@
+describe("correct behavior", () => {
+    test("basic functionality", () => {
+        const timeZone = new Temporal.TimeZone("UTC");
+        const zonedDateTime = new Temporal.ZonedDateTime(1625614921000000000n, timeZone);
+        expect(zonedDateTime.monthsInYear).toBe(12);
+    });
+});
+
+test("errors", () => {
+    test("this value must be a Temporal.ZonedDateTime object", () => {
+        expect(() => {
+            Reflect.get(Temporal.ZonedDateTime.prototype, "monthsInYear", "foo");
+        }).toThrowWithMessage(TypeError, "Not a Temporal.ZonedDateTime");
+    });
+});