fix: dateFieldName should throw error if locale dateFields are not loaded

Author: danielkaradachki

src/cldr/date-field-name.js

@@ -1,8 +1,13 @@
 import { localeInfo } from './info';
+import { errors } from '../errors';
 
 export default function dateFieldName(options, locale = "en") {
     const info = localeInfo(locale);
-    const dateFields = info.calendar.dateFields || {};
+    const dateFields = info.calendar.dateFields;
+    if (!dateFields) {
+        throw errors.NoDateFieldNames.error();
+    }
+
     const fieldNameInfo = dateFields[options.type] || {};
 
     return fieldNameInfo[options.nameType] || fieldNameInfo['wide'];

src/error-details.js

@@ -10,5 +10,6 @@ export default {
     "NoGMTInfo": "Cannot determine locale GMT format. Please load the locale timeZoneNames data.",
     "NoWeekData": "Cannot determine locale first day of week. Please load the supplemental weekData.",
     "NoFirstDay": "Cannot determine locale first day of week. Please load the supplemental weekData. The default culture includes only the 'en-US' first day info.",
-    "NoValidCurrency": "Cannot determine a default currency for the {0} locale. Please specify explicitly the currency with the format options."
+    "NoValidCurrency": "Cannot determine a default currency for the {0} locale. Please specify explicitly the currency with the format options.",
+    "NoDateFieldNames": "Cannot determine the locale date field names. Please load the locale dateFields data."
 };

test/cldr.js

@@ -379,6 +379,20 @@ describe('dateFormatNames', () => {
 });
 
 describe('dateFieldName', () => {
+    it('should throw error if locale dateFields are not available', () => {
+        const calendar = cldr.en.calendar;
+        const dateFields = calendar.dateFields;
+        delete calendar.dateFields;
+        try {
+            expect(() => {
+                dateFieldName({ type: 'day', nameType: 'wide' });
+            }).toThrowError(/Cannot determine the locale date field names/);
+        } finally {
+            calendar.dateFields = dateFields;
+        }
+
+    });
+
     it('should return placeholder for the era type', () => {
         expect(dateFieldName({ type: 'era', nameType: 'wide' })).toEqual("era");
         expect(dateFieldName({ type: 'era', nameType: 'narrow' })).toEqual("era");