Add simple polyfill for Intl.ListFormat

src/impl/locale.js

@@ -1,4 +1,11 @@
-import { hasLocaleWeekInfo, hasRelative, padStart, roundTo, validateWeekSettings } from "./util.js";
+import {
+  hasList,
+  hasLocaleWeekInfo,
+  hasRelative,
+  padStart,
+  roundTo,
+  validateWeekSettings,
+} from "./util.js";
 import * as English from "./english.js";
 import Settings from "../settings.js";
 import DateTime from "../datetime.js";
@@ -317,6 +324,26 @@ class PolyRelFormatter {
   }
 }
 
+/**
+ * @private
+ */
+class PolyListFormatter {
+  constructor(intl, opts) {
+    this.opts = opts;
+    if (hasList()) {
+      this.lf = getCachedLF(intl, opts);
+    }
+  }
+
+  format(list) {
+    if (this.lf) {
+      return this.lf.format(list);
+    } else {
+      return list.join(", ");
+    }
+  }
+}
+
 const fallbackWeekSettings = {
   firstDay: 1,
   minimalDays: 4,
@@ -499,7 +526,7 @@ export default class Locale {
   }
 
   listFormatter(opts = {}) {
-    return getCachedLF(this.intl, opts);
+    return new PolyListFormatter(this.intl, opts);
   }
 
   isEnglish() {

src/impl/util.js

@@ -44,6 +44,14 @@ export function hasRelative() {
   }
 }
 
+export function hasList() {
+  try {
+    return typeof Intl !== "undefined" && !!Intl.ListFormat;
+  } catch (e) {
+    return false;
+  }
+}
+
 export function hasLocaleWeekInfo() {
   try {
     return (

test/duration/format.test.js

@@ -1,6 +1,8 @@
 /* global test expect */
 import { Duration } from "../../src/luxon";
 
+const Helpers = require("../helpers");
+
 const dur = () =>
   Duration.fromObject({
     years: 1,
@@ -314,3 +316,15 @@ test("Duration#toHuman works in differt languages", () => {
     "1 an, 2 mois, 1 semaine, 3 jours, 4 heures, 5 minutes, 6 secondes, 7 millisecondes"
   );
 });
+
+Helpers.withoutLF("Duration#toHuman works without LF", () => {
+  expect(dur().toHuman()).toEqual(
+    "1 year, 2 months, 1 week, 3 days, 4 hours, 5 minutes, 6 seconds, 7 milliseconds"
+  );
+});
+
+Helpers.withoutLF("Duration#toHuman falls back to commas", () => {
+  expect(dur().reconfigure({ locale: "ja" }).toHuman()).toEqual(
+    "1 年, 2 か月, 1 週間, 3 日, 4 時間, 5 分, 6 秒, 7 ミリ秒"
+  );
+});

test/helpers.js

@@ -15,6 +15,20 @@ exports.withoutRTF = function (name, f) {
   });
 };
 
+exports.withoutLF = function (name, f) {
+  const fullName = `With no ListFormat support, ${name}`;
+  test(fullName, () => {
+    const rtf = Intl.ListFormat;
+    try {
+      Intl.ListFormat = undefined;
+      Settings.resetCaches();
+      f();
+    } finally {
+      Intl.ListFormat = rtf;
+    }
+  });
+};
+
 exports.withoutLocaleWeekInfo = function (name, f) {
   const fullName = `With no Intl.Locale.weekInfo support, ${name}`;
   test(fullName, () => {