fix: Allow default initialization of DateTime/Duration/Interval

src/datetime.js

@@ -514,6 +514,10 @@ export default class DateTime {
    * @access private
    */
   constructor(config) {
+    if (!config) {
+      return DateTime.invalid("no config supplied");
+    }
+
     const zone = config.zone || Settings.defaultZone;
 
     let invalid =

src/duration.js

@@ -218,6 +218,10 @@ export default class Duration {
    * @private
    */
   constructor(config) {
+    if (!config) {
+      return Duration.invalid("no config supplied");
+    }
+
     const accurate = config.conversionAccuracy === "longterm" || false;
     let matrix = accurate ? accurateMatrix : casualMatrix;
 

src/impl/locale.js

@@ -360,7 +360,9 @@ export default class Locale {
   }
 
   constructor(locale, numbering, outputCalendar, weekSettings, specifiedLocale) {
-    const [parsedLocale, parsedNumberingSystem, parsedOutputCalendar] = parseLocaleString(locale);
+    const [parsedLocale, parsedNumberingSystem, parsedOutputCalendar] = parseLocaleString(
+      locale || systemLocale()
+    );
 
     this.locale = parsedLocale;
     this.numberingSystem = numbering || parsedNumberingSystem || null;

src/interval.js

@@ -41,6 +41,10 @@ export default class Interval {
    * @private
    */
   constructor(config) {
+    if (!config) {
+      return Interval.invalid("no config supplied");
+    }
+
     /**
      * @access private
      */

test/datetime/create.test.js

@@ -9,6 +9,15 @@ const withDefaultLocale = Helpers.withDefaultLocale,
   withthrowOnInvalid = Helpers.setUnset("throwOnInvalid"),
   withDefaultZone = Helpers.withDefaultZone;
 
+//------
+// new
+//------
+test("Default constructor works and returns an invalid instance", () => {
+  const datetime = new DateTime();
+  expect(datetime.isValid).toBe(false);
+  expect(datetime.invalidReason).toBe("no config supplied");
+});
+
 //------
 // .now()
 //------

test/duration/create.test.js

@@ -2,6 +2,15 @@
 
 import { Duration } from "../../src/luxon";
 
+//------
+// new
+//------
+test("Default constructor works and returns an invalid instance", () => {
+  const duration = new Duration();
+  expect(duration.isValid).toBe(false);
+  expect(duration.invalidReason).toBe("no config supplied");
+});
+
 //------
 // .fromObject()
 //-------

test/interval/create.test.js

@@ -4,6 +4,15 @@ import Helpers from "../helpers";
 
 const withThrowOnInvalid = Helpers.setUnset("throwOnInvalid");
 
+//------
+// new
+//------
+test("Default constructor works and returns an invalid instance", () => {
+  const interval = new Interval();
+  expect(interval.isValid).toBe(false);
+  expect(interval.invalidReason).toBe("no config supplied");
+});
+
 //------
 // .fromObject()
 //-------