LibJS: Implement Temporal.PlainTime.prototype.toLocaleString()

Author: https://github.com/linusg
Commit: https://github.com/SerenityOS/serenity/commit/6987e326d89
Pull-request: https://github.com/SerenityOS/serenity/pull/9903
Reviewed-by: https://github.com/IdanHo ✅

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

@@ -43,6 +43,7 @@ void PlainTimePrototype::initialize(GlobalObject& global_object)
     define_native_function(vm.names.toPlainDateTime, to_plain_date_time, 1, attr);
     define_native_function(vm.names.getISOFields, get_iso_fields, 0, 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.valueOf, value_of, 0, attr);
 }
 
@@ -389,6 +390,21 @@ JS_DEFINE_NATIVE_FUNCTION(PlainTimePrototype::to_string)
     return js_string(vm, move(string));
 }
 
+// 4.3.21 Temporal.PlainTime.prototype.toLocaleString ( [ locales [ , options ] ] ), https://tc39.es/proposal-temporal/#sec-temporal.plaintime.prototype.tolocalestring
+JS_DEFINE_NATIVE_FUNCTION(PlainTimePrototype::to_locale_string)
+{
+    // 1. Let temporalTime be the this value.
+    // 2. Perform ? RequireInternalSlot(temporalTime, [[InitializedTemporalTime]]).
+    auto* temporal_time = typed_this(global_object);
+    if (vm.exception())
+        return {};
+
+    // FIXME: Hey spec, this cannot fail...
+    // 3. Return ? TemporalTimeToString(temporalTime.[[ISOHour]], temporalTime.[[ISOMinute]], temporalTime.[[ISOSecond]], temporalTime.[[ISOMillisecond]], temporalTime.[[ISOMicrosecond]], temporalTime.[[ISONanosecond]], "auto").
+    auto string = temporal_time_to_string(temporal_time->iso_hour(), temporal_time->iso_minute(), temporal_time->iso_second(), temporal_time->iso_millisecond(), temporal_time->iso_microsecond(), temporal_time->iso_nanosecond(), "auto"sv);
+    return js_string(vm, move(string));
+}
+
 // 4.3.23 Temporal.PlainTime.prototype.valueOf ( ), https://tc39.es/proposal-temporal/#sec-temporal.plaintime.prototype.valueof
 JS_DEFINE_NATIVE_FUNCTION(PlainTimePrototype::value_of)
 {

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

@@ -31,6 +31,7 @@ private:
     JS_DECLARE_NATIVE_FUNCTION(to_plain_date_time);
     JS_DECLARE_NATIVE_FUNCTION(get_iso_fields);
     JS_DECLARE_NATIVE_FUNCTION(to_string);
+    JS_DECLARE_NATIVE_FUNCTION(to_locale_string);
     JS_DECLARE_NATIVE_FUNCTION(value_of);
 };
 

Userland/Libraries/LibJS/Tests/builtins/Temporal/PlainTime/PlainTime.prototype.toLocaleString.js

@@ -0,0 +1,18 @@
+describe("correct behavior", () => {
+    test("length is 0", () => {
+        expect(Temporal.PlainTime.prototype.toLocaleString).toHaveLength(0);
+    });
+
+    test("basic functionality", () => {
+        const plainTime = new Temporal.PlainTime(18, 14, 47, 123, 456, 789);
+        expect(plainTime.toLocaleString()).toBe("18:14:47.123456789");
+    });
+});
+
+describe("errors", () => {
+    test("this value must be a Temporal.PlainTime object", () => {
+        expect(() => {
+            Temporal.PlainTime.prototype.toLocaleString.call("foo");
+        }).toThrowWithMessage(TypeError, "Not a Temporal.PlainTime");
+    });
+});