LibJS: Implement Temporal.PlainDate.prototype.withCalendar

Userland/Libraries/LibJS/Runtime/CommonPropertyNames.h

@@ -382,6 +382,7 @@ namespace JS {
     P(warn)                                  \
     P(weeks)                                 \
     P(with)                                  \
+    P(withCalendar)                          \
     P(writable)                              \
     P(year)                                  \
     P(years)

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

@@ -29,6 +29,7 @@ void PlainDatePrototype::initialize(GlobalObject& global_object)
     define_native_accessor(vm.names.calendar, calendar_getter, {}, Attribute::Configurable);
 
     u8 attr = Attribute::Writable | Attribute::Configurable;
+    define_native_function(vm.names.withCalendar, with_calendar, 1, attr);
     define_native_function(vm.names.equals, equals, 1, attr);
     define_native_function(vm.names.valueOf, value_of, 0, attr);
 }
@@ -59,6 +60,24 @@ JS_DEFINE_NATIVE_FUNCTION(PlainDatePrototype::calendar_getter)
     return Value(&temporal_date->calendar());
 }
 
+// 3.3.22 Temporal.PlainDate.prototype.withCalendar ( calendar ), https://tc39.es/proposal-temporal/#sec-temporal.plaindate.prototype.withcalendar
+JS_DEFINE_NATIVE_FUNCTION(PlainDatePrototype::with_calendar)
+{
+    // 1. Let temporalDate be the this value.
+    // 2. Perform ? RequireInternalSlot(temporalDate, [[InitializedTemporalDate]]).
+    auto* temporal_date = typed_this(global_object);
+    if (vm.exception())
+        return {};
+
+    // 3. Let calendar be ? ToTemporalCalendar(calendar).
+    auto calendar = to_temporal_calendar(global_object, vm.argument(0));
+    if (vm.exception())
+        return {};
+
+    // 4. Return ? CreateTemporalDate(temporalDate.[[ISOYear]], temporalDate.[[ISOMonth]], temporalDate.[[ISODay]], calendar).
+    return create_temporal_date(global_object, temporal_date->iso_year(), temporal_date->iso_month(), temporal_date->iso_day(), *calendar);
+}
+
 // 3.3.25 Temporal.PlainDate.prototype.equals ( other ), https://tc39.es/proposal-temporal/#sec-temporal.plaindate.prototype.equals
 JS_DEFINE_NATIVE_FUNCTION(PlainDatePrototype::equals)
 {

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

@@ -21,6 +21,7 @@ public:
 private:
     JS_DECLARE_NATIVE_FUNCTION(calendar_getter);
 
+    JS_DECLARE_NATIVE_FUNCTION(with_calendar);
     JS_DECLARE_NATIVE_FUNCTION(equals);
     JS_DECLARE_NATIVE_FUNCTION(value_of);
 };

Userland/Libraries/LibJS/Tests/builtins/Temporal/PlainDate/PlainDate.prototype.withCalendar.js

@@ -0,0 +1,13 @@
+describe("correct behavior", () => {
+    test("length is 1", () => {
+        expect(Temporal.PlainDate.prototype.withCalendar).toHaveLength(1);
+    });
+
+    test("basic functionality", () => {
+        const calendar = { hello: "friends" };
+        const firstPlainDate = new Temporal.PlainDate(1, 1, 1);
+        expect(firstPlainDate.calendar).not.toBe(calendar);
+        const secondPlainDate = firstPlainDate.withCalendar(calendar);
+        expect(secondPlainDate.calendar).toBe(calendar);
+    });
+});