LibJS: Implement Temporal.PlainYearMonth.prototype.toString()

Author: https://github.com/linusg
Commit: https://github.com/SerenityOS/serenity/commit/421ad73b4ff
Pull-request: https://github.com/SerenityOS/serenity/pull/9510
Reviewed-by: https://github.com/IdanHo ✅

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

@@ -7,6 +7,7 @@
 #include <LibJS/Runtime/AbstractOperations.h>
 #include <LibJS/Runtime/GlobalObject.h>
 #include <LibJS/Runtime/Temporal/AbstractOperations.h>
+#include <LibJS/Runtime/Temporal/Calendar.h>
 #include <LibJS/Runtime/Temporal/PlainDate.h>
 #include <LibJS/Runtime/Temporal/PlainYearMonth.h>
 #include <LibJS/Runtime/Temporal/PlainYearMonthConstructor.h>
@@ -186,4 +187,37 @@ PlainYearMonth* create_temporal_year_month(GlobalObject& global_object, i32 iso_
     return object;
 }
 
+// 9.5.8 TemporalYearMonthToString ( yearMonth, showCalendar ), https://tc39.es/proposal-temporal/#sec-temporal-temporalyearmonthtostring
+Optional<String> temporal_year_month_to_string(GlobalObject& global_object, PlainYearMonth& year_month, StringView show_calendar)
+{
+    auto& vm = global_object.vm();
+
+    // 1. Assert: Type(yearMonth) is Object.
+    // 2. Assert: yearMonth has an [[InitializedTemporalYearMonth]] internal slot.
+
+    // 3. Let year be ! PadISOYear(yearMonth.[[ISOYear]]).
+    // 4. Let month be yearMonth.[[ISOMonth]] formatted as a two-digit decimal number, padded to the left with a zero if necessary.
+    // 5. Let result be the string-concatenation of year, the code unit 0x002D (HYPHEN-MINUS), and month.
+    auto result = String::formatted("{}-{:02}", pad_iso_year(year_month.iso_year()), year_month.iso_month());
+
+    // 6. Let calendarID be ? ToString(yearMonth.[[Calendar]]).
+    auto calendar_id = Value(&year_month.calendar()).to_string(global_object);
+    if (vm.exception())
+        return {};
+
+    // 7. If calendarID is not "iso8601", then
+    if (calendar_id != "iso8601") {
+        // a. Let day be yearMonth.[[ISODay]] formatted as a two-digit decimal number, padded to the left with a zero if necessary.
+        // b. Set result to the string-concatenation of result, the code unit 0x002D (HYPHEN-MINUS), and day.
+        result = String::formatted("{}-{:02}", result, year_month.iso_day());
+    }
+
+    // 8. Let calendarString be ! FormatCalendarAnnotation(calendarID, showCalendar).
+    auto calendar_string = format_calendar_annotation(calendar_id, show_calendar);
+
+    // 9. Set result to the string-concatenation of result and calendarString.
+    // 10. Return result.
+    return String::formatted("{}{}", result, calendar_string);
+}
+
 }

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

@@ -45,5 +45,6 @@ bool iso_year_month_within_limits(i32 year, u8 month);
 ISOYearMonth balance_iso_year_month(double year, double month);
 ISOYearMonth constrain_iso_year_month(double year, double month);
 PlainYearMonth* create_temporal_year_month(GlobalObject&, i32 iso_year, u8 iso_month, Object& calendar, u8 reference_iso_day, FunctionObject* new_target = nullptr);
+Optional<String> temporal_year_month_to_string(GlobalObject&, PlainYearMonth&, StringView show_calendar);
 
 }

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

@@ -6,6 +6,7 @@
 
 #include <AK/TypeCasts.h>
 #include <LibJS/Runtime/GlobalObject.h>
+#include <LibJS/Runtime/Temporal/AbstractOperations.h>
 #include <LibJS/Runtime/Temporal/Calendar.h>
 #include <LibJS/Runtime/Temporal/PlainYearMonth.h>
 #include <LibJS/Runtime/Temporal/PlainYearMonthPrototype.h>
@@ -37,6 +38,7 @@ void PlainYearMonthPrototype::initialize(GlobalObject& global_object)
     define_native_accessor(vm.names.inLeapYear, in_leap_year_getter, {}, Attribute::Configurable);
 
     u8 attr = Attribute::Writable | Attribute::Configurable;
+    define_native_function(vm.names.toString, to_string, 0, attr);
     define_native_function(vm.names.valueOf, value_of, 0, attr);
     define_native_function(vm.names.getISOFields, get_iso_fields, 0, attr);
 }
@@ -179,6 +181,33 @@ JS_DEFINE_NATIVE_FUNCTION(PlainYearMonthPrototype::in_leap_year_getter)
     return Value(calendar_in_leap_year(global_object, calendar, *year_month));
 }
 
+// 9.3.17 Temporal.PlainYearMonth.prototype.toString ( [ options ] ), https://tc39.es/proposal-temporal/#sec-temporal.plainyearmonth.prototype.tostring
+JS_DEFINE_NATIVE_FUNCTION(PlainYearMonthPrototype::to_string)
+{
+    // 1. Let yearMonth be the this value.
+    // 2. Perform ? RequireInternalSlot(yearMonth, [[InitializedTemporalYearMonth]]).
+    auto* year_month = typed_this(global_object);
+    if (vm.exception())
+        return {};
+
+    // 3. Set options to ? GetOptionsObject(options).
+    auto* options = get_options_object(global_object, vm.argument(0));
+    if (vm.exception())
+        return {};
+
+    // 4. Let showCalendar be ? ToShowCalendarOption(options).
+    auto show_calendar = to_show_calendar_option(global_object, *options);
+    if (vm.exception())
+        return {};
+
+    // 5. Return ? TemporalYearMonthToString(yearMonth, showCalendar).
+    auto string = temporal_year_month_to_string(global_object, *year_month, *show_calendar);
+    if (vm.exception())
+        return {};
+
+    return js_string(vm, *string);
+}
+
 // 9.3.20 Temporal.PlainYearMonth.prototype.valueOf ( ), https://tc39.es/proposal-temporal/#sec-temporal.plainyearmonth.prototype.valueof
 JS_DEFINE_NATIVE_FUNCTION(PlainYearMonthPrototype::value_of)
 {

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

@@ -27,6 +27,7 @@ private:
     JS_DECLARE_NATIVE_FUNCTION(days_in_month_getter);
     JS_DECLARE_NATIVE_FUNCTION(months_in_year_getter);
     JS_DECLARE_NATIVE_FUNCTION(in_leap_year_getter);
+    JS_DECLARE_NATIVE_FUNCTION(to_string);
     JS_DECLARE_NATIVE_FUNCTION(value_of);
     JS_DECLARE_NATIVE_FUNCTION(get_iso_fields);
 };

Userland/Libraries/LibJS/Tests/builtins/Temporal/PlainYearMonth/PlainYearMonth.prototype.toString.js

@@ -0,0 +1,51 @@
+describe("correct behavior", () => {
+    test("length is 0", () => {
+        expect(Temporal.PlainYearMonth.prototype.toString).toHaveLength(0);
+    });
+
+    test("basic functionality", () => {
+        let plainYearMonth;
+
+        plainYearMonth = new Temporal.PlainYearMonth(2021, 7);
+        expect(plainYearMonth.toString()).toBe("2021-07");
+        expect(plainYearMonth.toString({ calendarName: "auto" })).toBe("2021-07");
+        expect(plainYearMonth.toString({ calendarName: "always" })).toBe("2021-07[u-ca=iso8601]");
+        expect(plainYearMonth.toString({ calendarName: "never" })).toBe("2021-07");
+
+        plainYearMonth = new Temporal.PlainYearMonth(2021, 7, { toString: () => "foo" }, 6);
+        expect(plainYearMonth.toString()).toBe("2021-07-06[u-ca=foo]");
+        expect(plainYearMonth.toString({ calendarName: "auto" })).toBe("2021-07-06[u-ca=foo]");
+        expect(plainYearMonth.toString({ calendarName: "always" })).toBe("2021-07-06[u-ca=foo]");
+        expect(plainYearMonth.toString({ calendarName: "never" })).toBe("2021-07-06");
+
+        plainYearMonth = new Temporal.PlainYearMonth(0, 1);
+        expect(plainYearMonth.toString()).toBe("+000000-01");
+
+        plainYearMonth = new Temporal.PlainYearMonth(999, 1);
+        expect(plainYearMonth.toString()).toBe("+000999-01");
+
+        plainYearMonth = new Temporal.PlainYearMonth(12345, 1);
+        expect(plainYearMonth.toString()).toBe("+012345-01");
+
+        plainYearMonth = new Temporal.PlainYearMonth(123456, 1);
+        expect(plainYearMonth.toString()).toBe("+123456-01");
+
+        plainYearMonth = new Temporal.PlainYearMonth(-12345, 1);
+        expect(plainYearMonth.toString()).toBe("-012345-01");
+    });
+});
+
+describe("errors", () => {
+    test("this value must be a Temporal.PlainYearMonth object", () => {
+        expect(() => {
+            Temporal.PlainYearMonth.prototype.toString.call("foo");
+        }).toThrowWithMessage(TypeError, "Not a Temporal.PlainYearMonth");
+    });
+
+    test("calendarName option must be one of 'auto', 'always', 'never'", () => {
+        const plainYearMonth = new Temporal.PlainYearMonth(2021, 7);
+        expect(() => {
+            plainYearMonth.toString({ calendarName: "foo" });
+        }).toThrowWithMessage(RangeError, "foo is not a valid value for option calendarName");
+    });
+});