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

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

@@ -53,6 +53,7 @@ void PlainDatePrototype::initialize(GlobalObject& global_object)
     define_native_function(vm.names.equals, equals, 1, attr);
     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);
 }
 
@@ -443,6 +444,23 @@ JS_DEFINE_NATIVE_FUNCTION(PlainDatePrototype::to_locale_string)
     return js_string(vm, *string);
 }
 
+// 3.3.30 Temporal.PlainDate.prototype.toJSON ( ), https://tc39.es/proposal-temporal/#sec-temporal.plaindate.prototype.tojson
+JS_DEFINE_NATIVE_FUNCTION(PlainDatePrototype::to_json)
+{
+    // 1. Let temporalDate be the this value.
+    // 2. Perform ? RequireInternalSlot(temporalDate, [[InitializedTemporalDate]]).
+    auto* temporal_date = typed_this(global_object);
+    if (vm.exception())
+        return {};
+
+    // 3. Return ? TemporalDateToString(temporalDate, "auto").
+    auto string = temporal_date_to_string(global_object, *temporal_date, "auto"sv);
+    if (vm.exception())
+        return {};
+
+    return js_string(vm, *string);
+}
+
 // 3.3.31 Temporal.PlainDate.prototype.valueOf ( ), https://tc39.es/proposal-temporal/#sec-temporal.plaindate.prototype.valueof
 JS_DEFINE_NATIVE_FUNCTION(PlainDatePrototype::value_of)
 {

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

@@ -39,6 +39,7 @@ private:
     JS_DECLARE_NATIVE_FUNCTION(equals);
     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);
 };
 

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

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