LibJS: Implement Temporal.Calendar.prototype.weekOfYear

Userland/Libraries/LibJS/Runtime/CommonPropertyNames.h

@@ -382,6 +382,7 @@ namespace JS {
     P(valueOf)                               \
     P(values)                                \
     P(warn)                                  \
+    P(weekOfYear)                            \
     P(weeks)                                 \
     P(with)                                  \
     P(withCalendar)                          \

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

@@ -382,6 +382,21 @@ bool is_iso_leap_year(i32 year)
     return true;
 }
 
+// 12.1.31 ISODaysInYear ( year ), https://tc39.es/proposal-temporal/#sec-temporal-isodaysinyear
+u16 iso_days_in_year(i32 year)
+{
+    // 1. Assert: year is an integer.
+
+    // 2. If ! IsISOLeapYear(year) is true, then
+    if (is_iso_leap_year(year)) {
+        // a. Return 366.
+        return 366;
+    }
+
+    // 3. Return 365.
+    return 365;
+}
+
 // 12.1.32 ISODaysInMonth ( year, month ), https://tc39.es/proposal-temporal/#sec-temporal-isodaysinmonth
 i32 iso_days_in_month(i32 year, i32 month)
 {
@@ -441,6 +456,34 @@ u16 to_iso_day_of_year(i32 year, u8 month, u8 day)
     return days;
 }
 
+// 12.1.35 ToISOWeekOfYear ( year, month, day ), https://tc39.es/proposal-temporal/#sec-temporal-toisoweekofyear
+u8 to_iso_week_of_year(i32 year, u8 month, u8 day)
+{
+    // 1. Assert: year is an integer.
+    // 2. Assert: month is an integer.
+    // 3. Assert: day is an integer.
+
+    // 4. Let date be the date given by year, month, and day.
+    // 5. Return date's week number according to ISO-8601.
+    auto day_of_year = to_iso_day_of_year(year, month, day);
+    auto day_of_week = to_iso_day_of_week(year, month, day);
+    auto week = (day_of_year - day_of_week + 10) / 7;
+
+    if (week < 1) {
+        auto day_of_jump = to_iso_day_of_week(year, 1, 1);
+        if (day_of_jump == 5 || (is_iso_leap_year(year) && day_of_jump == 6))
+            return 53;
+        else
+            return 52;
+    } else if (week == 53) {
+        auto days_in_year = iso_days_in_year(year);
+        if (days_in_year - day_of_year < 4 - day_of_week)
+            return 1;
+    }
+
+    return week;
+}
+
 // 12.1.36 BuildISOMonthCode ( month ), https://tc39.es/proposal-temporal/#sec-buildisomonthcode
 String build_iso_month_code(i32 month)
 {

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

@@ -46,9 +46,11 @@ Object* get_temporal_calendar_with_iso_default(GlobalObject&, Object&);
 PlainDate* date_from_fields(GlobalObject&, Object& calendar, Object& fields, Object& options);
 bool calendar_equals(GlobalObject&, Object& one, Object& two);
 bool is_iso_leap_year(i32 year);
+u16 iso_days_in_year(i32 year);
 i32 iso_days_in_month(i32 year, i32 month);
 u8 to_iso_day_of_week(i32 year, u8 month, u8 day);
 u16 to_iso_day_of_year(i32 year, u8 month, u8 day);
+u8 to_iso_week_of_year(i32 year, u8 month, u8 day);
 String build_iso_month_code(i32 month);
 double resolve_iso_month(GlobalObject&, Object& fields);
 Optional<TemporalDate> iso_date_from_fields(GlobalObject&, Object& fields, Object& options);

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

@@ -37,6 +37,7 @@ void CalendarPrototype::initialize(GlobalObject& global_object)
     define_native_function(vm.names.day, day, 1, attr);
     define_native_function(vm.names.dayOfWeek, day_of_week, 1, attr);
     define_native_function(vm.names.dayOfYear, day_of_year, 1, attr);
+    define_native_function(vm.names.weekOfYear, week_of_year, 1, attr);
     define_native_function(vm.names.toString, to_string, 0, attr);
     define_native_function(vm.names.toJSON, to_json, 0, attr);
 }
@@ -254,6 +255,28 @@ JS_DEFINE_NATIVE_FUNCTION(CalendarPrototype::day_of_year)
     return Value(to_iso_day_of_year(temporal_date->iso_year(), temporal_date->iso_month(), temporal_date->iso_day()));
 }
 
+// 12.4.15 Temporal.Calendar.prototype.weekOfYear ( temporalDateLike ), https://tc39.es/proposal-temporal/#sec-temporal.calendar.prototype.weekofyear
+// NOTE: This is the minimum weekOfYear implementation for engines without ECMA-402.
+JS_DEFINE_NATIVE_FUNCTION(CalendarPrototype::week_of_year)
+{
+    // 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. Let temporalDate be ? ToTemporalDate(temporalDateLike).
+    auto* temporal_date = to_temporal_date(global_object, vm.argument(0));
+    if (vm.exception())
+        return {};
+
+    // 5. Return 𝔽(! ToISODayOfYear(temporalDate.[[ISOYear]], temporalDate.[[ISOMonth]], temporalDate.[[ISODay]])).
+    return Value(to_iso_week_of_year(temporal_date->iso_year(), temporal_date->iso_month(), temporal_date->iso_day()));
+}
+
 // 12.4.23 Temporal.Calendar.prototype.toString ( ), https://tc39.es/proposal-temporal/#sec-temporal.calendar.prototype.tostring
 JS_DEFINE_NATIVE_FUNCTION(CalendarPrototype::to_string)
 {

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

@@ -27,6 +27,7 @@ private:
     JS_DECLARE_NATIVE_FUNCTION(day);
     JS_DECLARE_NATIVE_FUNCTION(day_of_week);
     JS_DECLARE_NATIVE_FUNCTION(day_of_year);
+    JS_DECLARE_NATIVE_FUNCTION(week_of_year);
     JS_DECLARE_NATIVE_FUNCTION(to_string);
     JS_DECLARE_NATIVE_FUNCTION(to_json);
 };

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

@@ -0,0 +1,11 @@
+describe("correct behavior", () => {
+    test("length is 1", () => {
+        expect(Temporal.Calendar.prototype.weekOfYear).toHaveLength(1);
+    });
+
+    test("basic functionality", () => {
+        const calendar = new Temporal.Calendar("iso8601");
+        const date = new Temporal.PlainDate(2021, 7, 23);
+        expect(calendar.weekOfYear(date)).toBe(29);
+    });
+});