fix(common): fallback to last defined value for named date and time formats (#21299)

trotyl · mhevery · commit 879756d44c34 · 2018-01-18T13:39:00.000-06:00
closes #21282 PR Close #21299
diff --git a/packages/common/src/i18n/locale_data_api.ts b/packages/common/src/i18n/locale_data_api.ts
@@ -253,7 +253,7 @@ export function getLocaleWeekEndRange(locale: string): [WeekDay, WeekDay] {
  */
 export function getLocaleDateFormat(locale: string, width: FormatWidth): string {
   const data = findLocaleData(locale);
-  return data[LocaleDataIndex.DateFormat][width];
+  return getLastDefinedValue(data[LocaleDataIndex.DateFormat], width);
 }
 
 /**
@@ -278,7 +278,7 @@ export function getLocaleDateFormat(locale: string, width: FormatWidth): string
  */
 export function getLocaleTimeFormat(locale: string, width: FormatWidth): string {
   const data = findLocaleData(locale);
-  return data[LocaleDataIndex.TimeFormat][width];
+  return getLastDefinedValue(data[LocaleDataIndex.TimeFormat], width);
 }
 
 /**
diff --git a/packages/common/test/i18n/locale_data_api_spec.ts b/packages/common/test/i18n/locale_data_api_spec.ts
@@ -9,9 +9,10 @@
 import localeCaESVALENCIA from '@angular/common/locales/ca-ES-VALENCIA';
 import localeEn from '@angular/common/locales/en';
 import localeFr from '@angular/common/locales/fr';
+import localeZh from '@angular/common/locales/zh';
 import localeFrCA from '@angular/common/locales/fr-CA';
 import {registerLocaleData} from '../../src/i18n/locale_data';
-import {findLocaleData, getCurrencySymbol} from '../../src/i18n/locale_data_api';
+import {findLocaleData, getCurrencySymbol, getLocaleDateFormat, FormatWidth} from '../../src/i18n/locale_data_api';
 
 {
   describe('locale data api', () => {
@@ -22,6 +23,7 @@ import {findLocaleData, getCurrencySymbol} from '../../src/i18n/locale_data_api'
       registerLocaleData(localeFrCA);
       registerLocaleData(localeFr, 'fake-id');
       registerLocaleData(localeFrCA, 'fake_Id2');
+      registerLocaleData(localeZh);
     });
 
     describe('findLocaleData', () => {
@@ -64,5 +66,10 @@ import {findLocaleData, getCurrencySymbol} from '../../src/i18n/locale_data_api'
         expect(getCurrencySymbol('FAKE', 'narrow')).toEqual('FAKE');
       });
     });
+
+    describe('getLastDefinedValue', () => {
+      it('should find the last defined date format when format not defined',
+         () => { expect(getLocaleDateFormat('zh', FormatWidth.Long)).toEqual('y年M月d日'); });
+    });
   });
 }
