LibJS: Implement Temporal.PlainMonthDay.prototype.toJSON()

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

@@ -35,6 +35,7 @@ void PlainMonthDayPrototype::initialize(GlobalObject& global_object)
     u8 attr = Attribute::Writable | Attribute::Configurable;
     define_native_function(vm.names.toString, to_string, 0, attr);
     define_native_function(vm.names.toLocaleString, to_locale_string, 0, attr);
+    define_native_function(vm.names.toJSON, to_json, 0, attr);
     define_native_function(vm.names.valueOf, value_of, 0, attr);
     define_native_function(vm.names.getISOFields, get_iso_fields, 0, attr);
 }
@@ -142,6 +143,23 @@ JS_DEFINE_NATIVE_FUNCTION(PlainMonthDayPrototype::to_locale_string)
     return js_string(vm, *string);
 }
 
+// 10.3.10 Temporal.PlainMonthDay.prototype.toJSON ( ), https://tc39.es/proposal-temporal/#sec-temporal.plainmonthday.prototype.tojson
+JS_DEFINE_NATIVE_FUNCTION(PlainMonthDayPrototype::to_json)
+{
+    // 1. Let monthDay be the this value.
+    // 2. Perform ? RequireInternalSlot(monthDay, [[InitializedTemporalMonthDay]]).
+    auto* month_day = typed_this(global_object);
+    if (vm.exception())
+        return {};
+
+    // 3. Return ? TemporalMonthDayToString(monthDay, "auto").
+    auto string = temporal_month_day_to_string(global_object, *month_day, "auto"sv);
+    if (vm.exception())
+        return {};
+
+    return js_string(vm, *string);
+}
+
 // 10.3.11 Temporal.PlainMonthDay.prototype.valueOf ( ), https://tc39.es/proposal-temporal/#sec-temporal.plainmonthday.prototype.valueof
 JS_DEFINE_NATIVE_FUNCTION(PlainMonthDayPrototype::value_of)
 {

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

@@ -24,6 +24,7 @@ private:
     JS_DECLARE_NATIVE_FUNCTION(day_getter);
     JS_DECLARE_NATIVE_FUNCTION(to_string);
     JS_DECLARE_NATIVE_FUNCTION(to_locale_string);
+    JS_DECLARE_NATIVE_FUNCTION(to_json);
     JS_DECLARE_NATIVE_FUNCTION(value_of);
     JS_DECLARE_NATIVE_FUNCTION(get_iso_fields);
 };

Userland/Libraries/LibJS/Tests/builtins/Temporal/PlainMonthDay/PlainMonthDay.prototype.toJSON.js

@@ -0,0 +1,23 @@
+describe("correct behavior", () => {
+    test("length is 0", () => {
+        expect(Temporal.PlainMonthDay.prototype.toJSON).toHaveLength(0);
+    });
+
+    test("basic functionality", () => {
+        let plainMonthDay;
+
+        plainMonthDay = new Temporal.PlainMonthDay(7, 6);
+        expect(plainMonthDay.toJSON()).toBe("07-06");
+
+        plainMonthDay = new Temporal.PlainMonthDay(7, 6, { toString: () => "foo" }, 2021);
+        expect(plainMonthDay.toJSON()).toBe("2021-07-06[u-ca=foo]");
+    });
+});
+
+describe("errors", () => {
+    test("this value must be a Temporal.PlainMonthDay object", () => {
+        expect(() => {
+            Temporal.PlainMonthDay.prototype.toJSON.call("foo");
+        }).toThrowWithMessage(TypeError, "Not a Temporal.PlainMonthDay");
+    });
+});