LibJS: Implement Temporal.Calendar.prototype.monthDayFromFields()

Userland/Libraries/LibJS/Runtime/CommonPropertyNames.h

@@ -276,6 +276,7 @@ namespace JS {
     P(minutes)                               \
     P(month)                                 \
     P(monthCode)                             \
+    P(monthDayFromFields)                    \
     P(months)                                \
     P(monthsInYear)                          \
     P(multiline)                             \

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

@@ -787,6 +787,85 @@ Optional<ISOYearMonth> iso_year_month_from_fields(GlobalObject& global_object, O
     return ISOYearMonth { .year = result->year, .month = result->month, .reference_iso_day = 1 };
 }
 
+// 12.1.40 ISOMonthDayFromFields ( fields, options ), https://tc39.es/proposal-temporal/#sec-temporal-isomonthdayfromfields
+Optional<ISOMonthDay> iso_month_day_from_fields(GlobalObject& global_object, Object& fields, Object& options)
+{
+    auto& vm = global_object.vm();
+
+    // 1. Assert: Type(fields) is Object.
+
+    // 2. Let overflow be ? ToTemporalOverflow(options).
+    auto overflow = to_temporal_overflow(global_object, options);
+    if (vm.exception())
+        return {};
+
+    // 3. Set fields to ? PrepareTemporalFields(fields, « "day", "month", "monthCode", "year" », «»).
+    auto* prepared_fields = prepare_temporal_fields(global_object, fields, { "day"sv, "month"sv, "monthCode"sv, "year"sv }, {});
+    if (vm.exception())
+        return {};
+
+    // 4. Let month be ? Get(fields, "month").
+    auto month_value = prepared_fields->get(vm.names.month);
+    if (vm.exception())
+        return {};
+
+    // 5. Let monthCode be ? Get(fields, "monthCode").
+    auto month_code = prepared_fields->get(vm.names.monthCode);
+    if (vm.exception())
+        return {};
+
+    // 6. Let year be ? Get(fields, "year").
+    auto year = prepared_fields->get(vm.names.year);
+    if (vm.exception())
+        return {};
+
+    // 7. If month is not undefined, and monthCode and year are both undefined, then
+    if (!month_value.is_undefined() && month_code.is_undefined() && year.is_undefined()) {
+        // a. Throw a TypeError exception.
+        vm.throw_exception<TypeError>(global_object, ErrorType::TemporalMissingRequiredProperty, "monthCode or year");
+        return {};
+    }
+
+    // 8. Set month to ? ResolveISOMonth(fields).
+    auto month = resolve_iso_month(global_object, *prepared_fields);
+    if (vm.exception())
+        return {};
+
+    // 9. Let day be ? Get(fields, "day").
+    auto day = prepared_fields->get(vm.names.day);
+    if (vm.exception())
+        return {};
+
+    // 10. If day is undefined, throw a TypeError exception.
+    if (day.is_undefined()) {
+        vm.throw_exception<TypeError>(global_object, ErrorType::TemporalMissingRequiredProperty, vm.names.day.as_string());
+        return {};
+    }
+
+    // 11. Let referenceISOYear be 1972 (the first leap year after the Unix epoch).
+    i32 reference_iso_year = 1972;
+
+    Optional<ISODate> result;
+
+    // 12. If monthCode is undefined, then
+    if (month_code.is_undefined()) {
+        // a. Let result be ? RegulateISODate(year, month, day, overflow).
+        result = regulate_iso_date(global_object, year.as_double(), month, day.as_double(), *overflow);
+        if (vm.exception())
+            return {};
+    }
+    // 13. Else,
+    else {
+        // a. Let result be ? RegulateISODate(referenceISOYear, month, day, overflow).
+        result = regulate_iso_date(global_object, reference_iso_year, month, day.as_double(), *overflow);
+        if (vm.exception())
+            return {};
+    }
+
+    // 14. Return the new Record { [[Month]]: result.[[Month]], [[Day]]: result.[[Day]], [[ReferenceISOYear]]: referenceISOYear }.
+    return ISOMonthDay { .month = result->month, .day = result->day, .reference_iso_year = reference_iso_year };
+}
+
 // 12.1.41 ISOYear ( temporalObject ), https://tc39.es/proposal-temporal/#sec-temporal-isoyear
 i32 iso_year(Object& temporal_object)
 {

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

@@ -9,6 +9,7 @@
 
 #include <LibJS/Runtime/Object.h>
 #include <LibJS/Runtime/Temporal/PlainDate.h>
+#include <LibJS/Runtime/Temporal/PlainMonthDay.h>
 #include <LibJS/Runtime/Temporal/PlainYearMonth.h>
 #include <LibJS/Runtime/Value.h>
 
@@ -62,6 +63,7 @@ String build_iso_month_code(u8 month);
 double resolve_iso_month(GlobalObject&, Object& fields);
 Optional<ISODate> iso_date_from_fields(GlobalObject&, Object& fields, Object& options);
 Optional<ISOYearMonth> iso_year_month_from_fields(GlobalObject&, Object& fields, Object& options);
+Optional<ISOMonthDay> iso_month_day_from_fields(GlobalObject&, Object& fields, Object& options);
 i32 iso_year(Object& temporal_object);
 u8 iso_month(Object& temporal_object);
 String iso_month_code(Object& temporal_object);

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

@@ -36,6 +36,7 @@ void CalendarPrototype::initialize(GlobalObject& global_object)
     u8 attr = Attribute::Writable | Attribute::Configurable;
     define_native_function(vm.names.dateFromFields, date_from_fields, 2, attr);
     define_native_function(vm.names.yearMonthFromFields, year_month_from_fields, 2, attr);
+    define_native_function(vm.names.monthDayFromFields, month_day_from_fields, 2, attr);
     define_native_function(vm.names.year, year, 1, attr);
     define_native_function(vm.names.month, month, 1, attr);
     define_native_function(vm.names.monthCode, month_code, 1, attr);
@@ -144,6 +145,40 @@ JS_DEFINE_NATIVE_FUNCTION(CalendarPrototype::year_month_from_fields)
     return create_temporal_year_month(global_object, result->year, result->month, *calendar, result->reference_iso_day);
 }
 
+// 12.4.6 Temporal.Calendar.prototype.monthDayFromFields ( fields, options ), https://tc39.es/proposal-temporal/#sec-temporal.calendar.prototype.monthdayfromfields
+// NOTE: This is the minimum monthDayFromFields implementation for engines without ECMA-402.
+JS_DEFINE_NATIVE_FUNCTION(CalendarPrototype::month_day_from_fields)
+{
+    // 1. Let calendar be the this value.
+    // 2. Perform ? RequireInternalSlot(calendar, [[InitializedTemporalCalendar]]).
+    auto* calendar = typed_this(global_object);
+    if (vm.exception())
+        return {};
+
+    // 3. Assert: calendar.[[Identifier]] is "iso8601".
+    VERIFY(calendar->identifier() == "iso8601"sv);
+
+    // 4. If Type(fields) is not Object, throw a TypeError exception.
+    auto fields = vm.argument(0);
+    if (!fields.is_object()) {
+        vm.throw_exception<TypeError>(global_object, ErrorType::NotAnObject, fields.to_string_without_side_effects());
+        return {};
+    }
+
+    // 5. Set options to ? GetOptionsObject(options).
+    auto* options = get_options_object(global_object, vm.argument(1));
+    if (vm.exception())
+        return {};
+
+    // 6. Let result be ? ISOMonthDayFromFields(fields, options).
+    auto result = iso_month_day_from_fields(global_object, fields.as_object(), *options);
+    if (vm.exception())
+        return {};
+
+    // 7. Return ? CreateTemporalMonthDay(result.[[Month]], result.[[Day]], calendar, result.[[ReferenceISOYear]]).
+    return create_temporal_month_day(global_object, result->month, result->day, *calendar, result->reference_iso_year);
+}
+
 // 12.4.9 Temporal.Calendar.prototype.year ( temporalDateLike ), https://tc39.es/proposal-temporal/#sec-temporal.calendar.prototype.year
 // NOTE: This is the minimum year implementation for engines without ECMA-402.
 JS_DEFINE_NATIVE_FUNCTION(CalendarPrototype::year)

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

@@ -22,6 +22,7 @@ private:
     JS_DECLARE_NATIVE_FUNCTION(id_getter);
     JS_DECLARE_NATIVE_FUNCTION(date_from_fields);
     JS_DECLARE_NATIVE_FUNCTION(year_month_from_fields);
+    JS_DECLARE_NATIVE_FUNCTION(month_day_from_fields);
     JS_DECLARE_NATIVE_FUNCTION(year);
     JS_DECLARE_NATIVE_FUNCTION(month);
     JS_DECLARE_NATIVE_FUNCTION(month_code);

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

@@ -33,6 +33,12 @@ private:
     Object& m_calendar;   // [[Calendar]]
 };
 
+struct ISOMonthDay {
+    u8 month;
+    u8 day;
+    i32 reference_iso_year;
+};
+
 PlainMonthDay* create_temporal_month_day(GlobalObject&, u8 iso_month, u8 iso_day, Object& calendar, i32 reference_iso_year, FunctionObject* new_target = nullptr);
 
 }

Userland/Libraries/LibJS/Tests/builtins/Temporal/Calendar/Calendar.prototype.monthDayFromFields.js

@@ -0,0 +1,60 @@
+describe("correct behavior", () => {
+    test("length is 2", () => {
+        expect(Temporal.Calendar.prototype.monthDayFromFields).toHaveLength(2);
+    });
+
+    test("basic functionality", () => {
+        const calendar = new Temporal.Calendar("iso8601");
+        const plainMonthDay = calendar.monthDayFromFields({ year: 2021, month: 7, day: 6 });
+        expect(plainMonthDay.calendar).toBe(calendar);
+        expect(plainMonthDay.monthCode).toBe("M07");
+        expect(plainMonthDay.day).toBe(6);
+
+        const fields = plainMonthDay.getISOFields();
+        expect(fields.isoYear).toBe(1972); // No, this isn't a mistake
+    });
+
+    test("with monthCode", () => {
+        const calendar = new Temporal.Calendar("iso8601");
+        const plainMonthDay = calendar.monthDayFromFields({ monthCode: "M07", day: 6 });
+        expect(plainMonthDay.calendar).toBe(calendar);
+        expect(plainMonthDay.monthCode).toBe("M07");
+        expect(plainMonthDay.day).toBe(6);
+
+        const fields = plainMonthDay.getISOFields();
+        expect(fields.isoYear).toBe(1972);
+    });
+});
+
+describe("errors", () => {
+    test("first argument must be an object", () => {
+        const calendar = new Temporal.Calendar("iso8601");
+        expect(() => {
+            calendar.monthDayFromFields(42);
+        }).toThrowWithMessage(TypeError, "42 is not an object");
+    });
+
+    test("month or monthCode field is required", () => {
+        const calendar = new Temporal.Calendar("iso8601");
+        expect(() => {
+            calendar.monthDayFromFields({ year: 2021 });
+        }).toThrowWithMessage(TypeError, "Required property month is missing or undefined");
+    });
+
+    test("day field is required", () => {
+        const calendar = new Temporal.Calendar("iso8601");
+        expect(() => {
+            calendar.monthDayFromFields({ year: 2021, month: 7 });
+        }).toThrowWithMessage(TypeError, "Required property day is missing or undefined");
+    });
+
+    test("monthCode or year field is required when month is given", () => {
+        const calendar = new Temporal.Calendar("iso8601");
+        expect(() => {
+            calendar.monthDayFromFields({ month: 7, day: 6 });
+        }).toThrowWithMessage(
+            TypeError,
+            "Required property monthCode or year is missing or undefined"
+        );
+    });
+});