MOBILE-4653 lang: Load dayjs locale

src/core/features/settings/pages/general/general.ts

@@ -139,7 +139,7 @@ export default class CoreSettingsGeneralPage {
         try {
             await CoreLang.changeCurrentLanguage(this.selectedLanguage);
         } finally {
-            const langName = this.languages.find((lang) => lang.code == this.selectedLanguage)?.name;
+            const langName = this.languages.find((lang) => lang.code === this.selectedLanguage)?.name;
 
             const buttons: AlertButton[] = [
                 {

src/core/services/lang.ts

@@ -186,8 +186,7 @@ export class CoreLangProvider {
      * @returns Promise resolved when the change is finished.
      */
     async changeCurrentLanguage(language: string): Promise<void> {
-        // Use british english when parent english is loaded.
-        dayjs.locale(language === 'en' ? 'en-gb' : language);
+        await this.loadDayJSLocale(language);
 
         const previousLanguage = this.currentLanguage ?? this.getDefaultLanguage();
 
@@ -218,6 +217,35 @@ export class CoreLangProvider {
         }
     }
 
+    /**
+     * Load the locale for DayJS.
+     *
+     * @param locale Locale to load.
+     */
+    protected async loadDayJSLocale(locale: string): Promise<void> {
+        // Use british english when parent english is loaded.
+        locale = locale === 'en' ? 'en-gb' : locale;
+
+        try {
+            await import('dayjs/locale/' + locale);
+            dayjs.locale(locale);
+        } catch {
+            if (locale === 'en' || locale === 'en-gb') {
+                return;
+            }
+            const parentLang = await this.getParentLanguageForLang(locale);
+            const parentLangUsingHyphen = locale.substring(0, locale.indexOf('-'));
+
+            if (parentLangUsingHyphen && parentLang === 'en' || parentLang === undefined) {
+                await this.loadDayJSLocale(parentLangUsingHyphen);
+
+                return;
+            }
+
+            await this.loadDayJSLocale(parentLang ?? 'en');
+        }
+    }
+
     /**
      * Clear current custom strings.
      */