Fallback on locale name from specific to generic

Author: markandey

src/code/data-loader.js

@@ -346,6 +346,27 @@ function loadLocaleData(packedCLDRZoneData) {
     });
 }
 
+function getLocale(locale) {
+    if (this.get(locale)) {
+        return this.get(locale);
+    }
+
+    const localeItems = locale.split('-');
+    const fallbackLocales = [];
+
+    for (let i = 0; i < localeItems.length - 1; i++) {
+        fallbackLocales.push(localeItems.slice(0, localeItems.length - i - 1).join('-'));
+    }
+
+    for (let j = 0; j < fallbackLocales.length; j++) {
+        if (this.get(fallbackLocales[j])) {
+            return this.get(fallbackLocales[j]);
+        }
+    }
+
+    return undefined;
+}
+
 /**
 * Class every loader is instance.
 * data files call load function on this object.
@@ -384,7 +405,9 @@ export default function dataloader(globalSpace) {
             globalSpace.Intl.<someNameSpace>.value      : will hold the value.
         */
         globalSpace.Intl._metaZoneData = new Loader();
-        globalSpace.Intl._localeData = new Loader(loadLocaleData);
+        globalSpace.Intl._localeData = new Loader(loadLocaleData, {
+            getLocale: getLocale
+        });
         globalSpace.Intl._timeZoneData = new Loader(loadTimeZoneData, {
             // this timeZone loader needs to modify _metaZoneData so it need access to global object.
             // this is why this function is bind to globalSpace

src/code/lookup-utill.js

@@ -126,7 +126,7 @@ function getTimeZoneOffsetInfo(timeZoneHistory, date) {
  */
 function getZoneNameForLocale({locale, ianaTimeZone, offset, isdst, isShort, timeStamp}) {
     const metaZoneName = getRelevantMetaZone(Intl._metaZoneData.get(ianaTimeZone), timeStamp, getGenericZoneName(offset));
-    const cldrZones = Intl._localeData.get(locale);
+    const cldrZones = Intl._localeData.getLocale(locale);
     const cldrZoneNamesThruMetaZone = (metaZoneName && cldrZones && cldrZones.metazone[metaZoneName]);
     const cldrZoneNamesThruIanaTimeZone = (cldrZones && cldrZones.zone && cldrZones.zone[ianaTimeZone]);
 

src/code/polyfill.js

@@ -124,7 +124,7 @@ export default function polyfill(globalSpace) {
         if (options.timeZoneName !== undefined) {
             // We need to include timeZoneName in date format.
             // Check if we have locale data to able to do that.
-            if (!(gIntl._localeData.get(resolvedLocale) && // availability of localedata
+            if (!(gIntl._localeData.getLocale(resolvedLocale) && // availability of localedata
                     Intl._metaZoneData.get(timeZone))) {   // availability of metaZone for this timeZone
                 throw new RangeError(`unsupported value "${options.timeZoneName}" for timeZone ${timeZone}. requires locale data for ${resolvedLocale}`);
             }

test/test-complete.js

@@ -276,4 +276,26 @@ describe('Polyfill with complete package', () => {
 			});
 		});
 	});
+
+	describe('globalSpace.Intl._localeData', () => {
+		const ld = Intl._localeData;
+
+		describe('getLocale', () => {
+			it('finds valid locale', () => {
+				assert(ld.getLocale('en-US-u-va-posix'));
+				assert(ld.getLocale('en'));
+			});
+
+			it('should not find an invalid locale', () => {
+				assert(!ld.getLocale('noooo-not-a-locale'));
+			});
+
+			it('fallsback on generic locale if specific locale is not found', () => {
+				const loadedLocales = Object.keys(ld.get());
+
+				loadedLocales.forEach(locale => assert(ld.getLocale(locale + '-abcd')));
+				loadedLocales.forEach(locale => assert(ld.getLocale(locale + '-abcd-bcb')));
+			});
+		});
+	});
 });