feat: map es_US to the es-us locale in the generate adapters

src/generate/dateFns.ts

@@ -31,7 +31,19 @@ import {
 import * as locales from 'date-fns/locale';
 import type { GenerateConfig } from '.';
 
+// date-fns has no es-US locale and its `es` locale starts the week on Monday.
+// The `es_US` picker locale means Spanish with the US week start, so keep the
+// Spanish formatting and override the first day of the week.
+const esUS: Locale = {
+  ...locales.es,
+  options: { ...locales.es.options, weekStartsOn: 0 },
+};
+
 const getLocale = (locale: string): Locale => {
+  if (locale === 'es_US') {
+    return esUS;
+  }
+
   return (
     locales[locale] || locales[locale.replace(/_/g, '')] || locales[locale.replace(/_.*$/g, '')]
   );

src/generate/dayjs.ts

@@ -39,6 +39,7 @@ const localeMap: IlocaleMapObject = {
   // el_GR:
   en_GB: 'en-gb',
   en_US: 'en',
+  es_US: 'es-us',
   // es_ES:
   // et_EE:
   // fa_IR:

tests/generate.spec.tsx

@@ -9,6 +9,7 @@ import { getMoment } from './util/commonUtil';
 import 'dayjs/locale/zh-cn';
 import 'dayjs/locale/ko';
 import 'dayjs/locale/fr';
+import 'dayjs/locale/es-us';
 import type { GenerateConfig } from '../src/generate';
 
 describe('Picker.Generate', () => {
@@ -415,3 +416,24 @@ describe('Generate:date-fns', () => {
     expect(dateFnsGenerateConfig.getMinute(parsed)).toEqual(30);
   });
 });
+
+
+describe('Generate: es_US', () => {
+  it('dayjs keeps the US week start and formats in Spanish', () => {
+    expect(dayjsGenerateConfig.locale.getWeekFirstDay('es_US')).toEqual(0);
+
+    const date = dayjsGenerateConfig.locale.parse('es_US', '2018-01-15', ['YYYY-MM-DD'])!;
+
+    expect(dayjsGenerateConfig.locale.format('es_US', date, 'MMMM')).toEqual('enero');
+    expect(dayjsGenerateConfig.locale.format('es_US', date, 'dddd')).toEqual('lunes');
+  });
+
+  it('date-fns keeps the US week start and formats in Spanish', () => {
+    expect(dateFnsGenerateConfig.locale.getWeekFirstDay('es_US')).toEqual(0);
+
+    const date = new Date(2018, 0, 15);
+
+    expect(dateFnsGenerateConfig.locale.format('es_US', date, 'MMMM')).toEqual('enero');
+    expect(dateFnsGenerateConfig.locale.format('es_US', date, 'EEEE')).toEqual('lunes');
+  });
+});