LibJS: Implement Temporal.PlainMonthDay/YearMonth.prototype.toPlainDate

Author: https://github.com/trflynn89
Commit: 46998e922a
Pull-request: https://github.com/LadybirdBrowser/ladybird/pull/2513
Reviewed-by: https://github.com/shannonbooth ✅

Libraries/LibJS/Tests/builtins/Temporal/PlainMonthDay/PlainMonthDay.prototype.toPlainDate.js

@@ -0,0 +1,27 @@
+describe("normal behavior", () => {
+    test("length is 1", () => {
+        expect(Temporal.PlainMonthDay.prototype.toPlainDate).toHaveLength(1);
+    });
+
+    test("basic functionality", () => {
+        const plainMonthDay = new Temporal.PlainMonthDay(7, 6);
+        const plainDate = plainMonthDay.toPlainDate({ year: 2021 });
+        expect(plainDate.equals(new Temporal.PlainDate(2021, 7, 6))).toBeTrue();
+    });
+});
+
+describe("errors", () => {
+    test("argument must be an object", () => {
+        const plainMonthDay = new Temporal.PlainMonthDay(7, 6);
+        expect(() => {
+            plainMonthDay.toPlainDate(42);
+        }).toThrowWithMessage(TypeError, "42 is not an object");
+    });
+
+    test("year field is required", () => {
+        const plainMonthDay = new Temporal.PlainMonthDay(7, 6);
+        expect(() => {
+            plainMonthDay.toPlainDate({});
+        }).toThrowWithMessage(TypeError, "Required property year is missing or undefined");
+    });
+});

Libraries/LibJS/Tests/builtins/Temporal/PlainYearMonth/PlainYearMonth.prototype.toPlainDate.js

@@ -0,0 +1,27 @@
+describe("normal behavior", () => {
+    test("length is 1", () => {
+        expect(Temporal.PlainYearMonth.prototype.toPlainDate).toHaveLength(1);
+    });
+
+    test("basic functionality", () => {
+        const plainYearMonth = new Temporal.PlainYearMonth(2021, 7);
+        const plainDate = plainYearMonth.toPlainDate({ day: 6 });
+        expect(plainDate.equals(new Temporal.PlainDate(2021, 7, 6))).toBeTrue();
+    });
+});
+
+describe("errors", () => {
+    test("argument must be an object", () => {
+        const plainYearMonth = new Temporal.PlainYearMonth(2021, 7);
+        expect(() => {
+            plainYearMonth.toPlainDate(42);
+        }).toThrowWithMessage(TypeError, "42 is not an object");
+    });
+
+    test("day field is required", () => {
+        const plainYearMonth = new Temporal.PlainYearMonth(2021, 7);
+        expect(() => {
+            plainYearMonth.toPlainDate({});
+        }).toThrowWithMessage(TypeError, "Required property day is missing or undefined");
+    });
+});