LibJS: Implement the Temporal.PlainDateTime constructor

And the simple Temporal.PlainDateTime.prototype getters, so that the
constructed Temporal.PlainDateTime may actually be validated.

Libraries/LibJS/Tests/builtins/Temporal/PlainDateTime/PlainDateTime.from.js

@@ -0,0 +1,171 @@
+describe("correct behavior", () => {
+    test("length is 1", () => {
+        expect(Temporal.PlainDateTime.from).toHaveLength(1);
+    });
+
+    test("PlainDate instance argument", () => {
+        const plainDate = new Temporal.PlainDate(2021, 7, 6);
+        const plainDateTime = Temporal.PlainDateTime.from(plainDate);
+        expect(plainDateTime.year).toBe(2021);
+        expect(plainDateTime.month).toBe(7);
+        expect(plainDateTime.day).toBe(6);
+        expect(plainDateTime.hour).toBe(0);
+        expect(plainDateTime.minute).toBe(0);
+        expect(plainDateTime.second).toBe(0);
+        expect(plainDateTime.millisecond).toBe(0);
+        expect(plainDateTime.microsecond).toBe(0);
+        expect(plainDateTime.nanosecond).toBe(0);
+    });
+
+    test("PlainDateTime instance argument", () => {
+        const plainDateTime_ = new Temporal.PlainDateTime(2021, 7, 6, 18, 14, 47);
+        const plainDateTime = Temporal.PlainDateTime.from(plainDateTime_);
+        expect(plainDateTime).not.toBe(plainDateTime_);
+        expect(plainDateTime.year).toBe(2021);
+        expect(plainDateTime.month).toBe(7);
+        expect(plainDateTime.day).toBe(6);
+        expect(plainDateTime.hour).toBe(18);
+        expect(plainDateTime.minute).toBe(14);
+        expect(plainDateTime.second).toBe(47);
+        expect(plainDateTime.millisecond).toBe(0);
+        expect(plainDateTime.microsecond).toBe(0);
+        expect(plainDateTime.nanosecond).toBe(0);
+    });
+
+    test("fields object argument", () => {
+        const object = {
+            year: 2021,
+            month: 7,
+            day: 6,
+            hour: 23,
+            minute: 42,
+            second: 1,
+            millisecond: 0,
+            microsecond: 0,
+            nanosecond: 0,
+        };
+        const plainDateTime = Temporal.PlainDateTime.from(object);
+        expect(plainDateTime.year).toBe(2021);
+        expect(plainDateTime.month).toBe(7);
+        expect(plainDateTime.day).toBe(6);
+        expect(plainDateTime.hour).toBe(23);
+        expect(plainDateTime.minute).toBe(42);
+        expect(plainDateTime.second).toBe(1);
+        expect(plainDateTime.millisecond).toBe(0);
+        expect(plainDateTime.microsecond).toBe(0);
+        expect(plainDateTime.nanosecond).toBe(0);
+    });
+
+    test("with 'constrain' overflow option", () => {
+        const object = {
+            year: 0,
+            month: 1,
+            day: 1,
+            hour: 24,
+            minute: 60,
+            second: 60,
+            millisecond: 1000,
+            microsecond: 1000,
+            nanosecond: 1000,
+        };
+        const plainDateTime = Temporal.PlainDateTime.from(object, { overflow: "constrain" });
+        expect(plainDateTime.year).toBe(0);
+        expect(plainDateTime.month).toBe(1);
+        expect(plainDateTime.day).toBe(1);
+        expect(plainDateTime.hour).toBe(23);
+        expect(plainDateTime.minute).toBe(59);
+        expect(plainDateTime.second).toBe(59);
+        expect(plainDateTime.millisecond).toBe(999);
+        expect(plainDateTime.microsecond).toBe(999);
+        expect(plainDateTime.nanosecond).toBe(999);
+    });
+
+    test("PlainDateTime string argument", () => {
+        const plainDateTime = Temporal.PlainDateTime.from("2021-07-06T23:42:01");
+        expect(plainDateTime.year).toBe(2021);
+        expect(plainDateTime.month).toBe(7);
+        expect(plainDateTime.day).toBe(6);
+        expect(plainDateTime.hour).toBe(23);
+        expect(plainDateTime.minute).toBe(42);
+        expect(plainDateTime.second).toBe(1);
+        expect(plainDateTime.millisecond).toBe(0);
+        expect(plainDateTime.microsecond).toBe(0);
+        expect(plainDateTime.nanosecond).toBe(0);
+    });
+});
+
+describe("errors", () => {
+    test("missing fields", () => {
+        expect(() => {
+            Temporal.PlainDateTime.from({ year: 0, month: 1 });
+        }).toThrowWithMessage(TypeError, "Required property day is missing or undefined");
+        expect(() => {
+            Temporal.PlainDateTime.from({ year: 0, day: 1 });
+        }).toThrowWithMessage(TypeError, "Required property month is missing or undefined");
+        expect(() => {
+            Temporal.PlainDateTime.from({ month: 1, day: 1 });
+        }).toThrowWithMessage(TypeError, "Required property year is missing or undefined");
+    });
+
+    test("with 'reject' overflow option", () => {
+        const values = [
+            [{ year: 1234567, month: 1, day: 1 }, "Invalid ISO date"],
+            [{ year: 0, month: 13, day: 1 }, "Invalid ISO date"],
+            [{ year: 0, month: 1, day: 32 }, "Invalid ISO date"],
+            [{ year: 0, month: 1, day: 1, hour: 24 }, "Invalid plain time"],
+            [{ year: 0, month: 1, day: 1, hour: 0, minute: 60 }, "Invalid plain time"],
+            [{ year: 0, month: 1, day: 1, hour: 0, minute: 0, second: 60 }, "Invalid plain time"],
+            [
+                { year: 0, month: 1, day: 1, hour: 0, minute: 0, second: 0, millisecond: 1000 },
+                "Invalid plain time",
+            ],
+            [
+                {
+                    year: 0,
+                    month: 1,
+                    day: 1,
+                    hour: 0,
+                    minute: 0,
+                    second: 0,
+                    millisecond: 0,
+                    microsecond: 1000,
+                },
+                "Invalid plain time",
+            ],
+            [
+                {
+                    year: 0,
+                    month: 1,
+                    day: 1,
+                    hour: 0,
+                    minute: 0,
+                    second: 0,
+                    millisecond: 0,
+                    microsecond: 0,
+                    nanosecond: 1000,
+                },
+                "Invalid plain time",
+            ],
+        ];
+        for (const [object, error] of values) {
+            expect(() => {
+                Temporal.PlainDateTime.from(object, { overflow: "reject" });
+            }).toThrowWithMessage(RangeError, error);
+        }
+    });
+
+    test("string must not contain a UTC designator", () => {
+        expect(() => {
+            Temporal.PlainDateTime.from("2021-07-06T23:42:01Z");
+        }).toThrowWithMessage(RangeError, "Invalid ISO date time");
+    });
+
+    test("extended year must not be negative zero", () => {
+        expect(() => {
+            Temporal.PlainDateTime.from("-000000-01-01");
+        }).toThrowWithMessage(RangeError, "Invalid ISO date time");
+        expect(() => {
+            Temporal.PlainDateTime.from("−000000-01-01"); // U+2212
+        }).toThrowWithMessage(RangeError, "Invalid ISO date time");
+    });
+});