LibJS: Implement Temporal.PlainYearMonth.from

Author: https://github.com/Lubrsi
Commit: https://github.com/SerenityOS/serenity/commit/092ec0cecf8
Pull-request: https://github.com/SerenityOS/serenity/pull/9907
Reviewed-by: https://github.com/IdanHo ✅
Reviewed-by: https://github.com/linusg ✅

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

@@ -28,6 +28,9 @@ void PlainYearMonthConstructor::initialize(GlobalObject& global_object)
     define_direct_property(vm.names.prototype, global_object.temporal_plain_year_month_prototype(), 0);
 
     define_direct_property(vm.names.length, Value(2), Attribute::Configurable);
+
+    u8 attr = Attribute::Writable | Attribute::Configurable;
+    define_native_function(vm.names.from, from, 1, attr);
 }
 
 // 9.1.1 Temporal.PlainYearMonth ( isoYear, isoMonth [ , calendarLike [ , referenceISODay ] ] ), https://tc39.es/proposal-temporal/#sec-temporal.plainyearmonth
@@ -89,4 +92,31 @@ Value PlainYearMonthConstructor::construct(FunctionObject& new_target)
     return create_temporal_year_month(global_object, y, m, *calendar, ref, &new_target);
 }
 
+// 9.2.2 Temporal.PlainYearMonth.from ( item [ , options ] ), https://tc39.es/proposal-temporal/#sec-temporal.plainyearmonth.from
+JS_DEFINE_NATIVE_FUNCTION(PlainYearMonthConstructor::from)
+{
+    // 1. Set options to ? GetOptionsObject(options).
+    auto* options = get_options_object(global_object, vm.argument(1));
+    if (vm.exception())
+        return {};
+
+    auto item = vm.argument(0);
+
+    // 2. If Type(item) is Object and item has an [[InitializedTemporalYearMonth]] internal slot, then
+    if (item.is_object() && is<PlainYearMonth>(item.as_object())) {
+        // a. Perform ? ToTemporalOverflow(options).
+        (void)to_temporal_overflow(global_object, *options);
+        if (vm.exception())
+            return {};
+
+        auto& plain_year_month_object = static_cast<PlainYearMonth&>(item.as_object());
+
+        // b. Return ? CreateTemporalYearMonth(item.[[ISOYear]], item.[[ISOMonth]], item.[[Calendar]], item.[[ISODay]]).
+        return create_temporal_year_month(global_object, plain_year_month_object.iso_year(), plain_year_month_object.iso_month(), plain_year_month_object.calendar(), plain_year_month_object.iso_day());
+    }
+
+    // 3. Return ? ToTemporalYearMonth(item, options).
+    return to_temporal_year_month(global_object, item, options);
+}
+
 }

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

@@ -23,6 +23,8 @@ public:
 
 private:
     virtual bool has_constructor() const override { return true; }
+
+    JS_DECLARE_NATIVE_FUNCTION(from);
 };
 
 }

Userland/Libraries/LibJS/Tests/builtins/Temporal/PlainYearMonth/PlainYearMonth.from.js

@@ -0,0 +1,83 @@
+describe("correct behavior", () => {
+    test("length is 1", () => {
+        expect(Temporal.PlainYearMonth.from).toHaveLength(1);
+    });
+
+    test("PlainDate instance argument", () => {
+        const plainDate = new Temporal.PlainDate(2021, 7, 6);
+        const plainYearMonth = Temporal.PlainYearMonth.from(plainDate);
+        expect(plainYearMonth.year).toBe(2021);
+        expect(plainYearMonth.month).toBe(7);
+        expect(plainYearMonth.monthCode).toBe("M07");
+        expect(plainYearMonth.daysInYear).toBe(365);
+        expect(plainYearMonth.daysInMonth).toBe(31);
+        expect(plainYearMonth.monthsInYear).toBe(12);
+        expect(plainYearMonth.inLeapYear).toBeFalse();
+    });
+
+    test("PlainYearMonth instance argument", () => {
+        const plainYearMonth_ = new Temporal.PlainYearMonth(2021, 7);
+        const plainYearMonth = Temporal.PlainYearMonth.from(plainYearMonth_);
+        expect(plainYearMonth.year).toBe(2021);
+        expect(plainYearMonth.month).toBe(7);
+        expect(plainYearMonth.monthCode).toBe("M07");
+        expect(plainYearMonth.daysInYear).toBe(365);
+        expect(plainYearMonth.daysInMonth).toBe(31);
+        expect(plainYearMonth.monthsInYear).toBe(12);
+        expect(plainYearMonth.inLeapYear).toBeFalse();
+    });
+
+    test("ZonedDateTime instance argument", () => {
+        const timeZone = new Temporal.TimeZone("UTC");
+        const zonedDateTime = new Temporal.ZonedDateTime(1625614921000000000n, timeZone);
+        const plainYearMonth = Temporal.PlainYearMonth.from(zonedDateTime);
+        expect(plainYearMonth.year).toBe(2021);
+        expect(plainYearMonth.month).toBe(7);
+        expect(plainYearMonth.monthCode).toBe("M07");
+        expect(plainYearMonth.daysInYear).toBe(365);
+        expect(plainYearMonth.daysInMonth).toBe(31);
+        expect(plainYearMonth.monthsInYear).toBe(12);
+        expect(plainYearMonth.inLeapYear).toBeFalse();
+    });
+
+    test("fields object argument", () => {
+        const object = {
+            year: 2021,
+            month: 7,
+        };
+        const plainYearMonth = Temporal.PlainYearMonth.from(object);
+        expect(plainYearMonth.year).toBe(2021);
+        expect(plainYearMonth.month).toBe(7);
+        expect(plainYearMonth.monthCode).toBe("M07");
+        expect(plainYearMonth.daysInYear).toBe(365);
+        expect(plainYearMonth.daysInMonth).toBe(31);
+        expect(plainYearMonth.monthsInYear).toBe(12);
+        expect(plainYearMonth.inLeapYear).toBeFalse();
+    });
+
+    // Un-skip once ParseISODateTime & ParseTemporalYearMonthString are fully implemented
+    test.skip("PlainYearMonth string argument", () => {
+        const plainYearMonth = Temporal.PlainYearMonth.from("2021-07-06T23:42:01Z");
+        expect(plainYearMonth.year).toBe(2021);
+        expect(plainYearMonth.month).toBe(7);
+        expect(plainYearMonth.monthCode).toBe("M07");
+        expect(plainYearMonth.daysInYear).toBe(365);
+        expect(plainYearMonth.daysInMonth).toBe(31);
+        expect(plainYearMonth.monthsInYear).toBe(12);
+        expect(plainYearMonth.inLeapYear).toBeFalse();
+    });
+});
+
+describe("errors", () => {
+    test("missing fields", () => {
+        expect(() => {
+            Temporal.PlainYearMonth.from({});
+        }).toThrowWithMessage(TypeError, "Required property year is missing or undefined");
+        expect(() => {
+            Temporal.PlainYearMonth.from({ year: 0 });
+        }).toThrowWithMessage(TypeError, "Required property month is missing or undefined");
+        expect(() => {
+            Temporal.PlainYearMonth.from({ month: 1 });
+        }).toThrowWithMessage(TypeError, "Required property year is missing or undefined");
+    });
+});