MOBILE-3615 menu: Use parent language if any on docs url

src/addons/block/myoverview/components/myoverview/addon-block-myoverview.html

@@ -51,7 +51,8 @@
                 [disabled]="showFilters.future == 'disabled'">
                 {{ 'addon.block_myoverview.future' | translate }}
             </ion-select-option>
-            <ion-select-option class="ion-text-wrap" value="past" *ngIf="showFilters.past != 'hidden'" [disabled]="showFilters.past == 'disabled'">
+            <ion-select-option class="ion-text-wrap" value="past" *ngIf="showFilters.past != 'hidden'"
+                [disabled]="showFilters.past == 'disabled'">
                 {{ 'addon.block_myoverview.past' | translate }}
             </ion-select-option>
             <ng-container *ngIf="showFilters.custom != 'hidden'">

src/core/services/lang.ts

@@ -118,6 +118,19 @@ export class CoreLangProvider {
         return value.charAt(0).toUpperCase() + value.slice(1);
     }
 
+    /**
+     * Get the parent language defined on the language strings.
+     *
+     * @param currentLanguage Current language.
+     * @returns If a parent language is set, return the index name.
+     */
+    getParentLanguage(currentLanguage: string): string | undefined {
+        const parentLang = Translate.instant('core.parentlanguage');
+        if (parentLang != '' && parentLang != 'core.parentlanguage' && parentLang != currentLanguage) {
+            return parentLang;
+        }
+    }
+
     /**
      * Change current language.
      *
@@ -131,9 +144,9 @@ export class CoreLangProvider {
         promises.push(new Promise((resolve, reject) => {
             CoreSubscriptions.once(Translate.use(language), data => {
                 // It's a language override, load the original one first.
-                const fallbackLang = Translate.instant('core.parentlanguage');
+                const fallbackLang = this.getParentLanguage(language);
 
-                if (fallbackLang != '' && fallbackLang != 'core.parentlanguage' && fallbackLang != language) {
+                if (fallbackLang) {
                     CoreSubscriptions.once(
                         Translate.use(fallbackLang),
                         fallbackData => {

src/core/services/utils/url.ts

@@ -242,7 +242,8 @@ export class CoreUrlUtilsProvider {
         }
 
         try {
-            const lang = await CoreLang.getCurrentLanguage();
+            let lang = await CoreLang.getCurrentLanguage();
+            lang = CoreLang.getParentLanguage(lang) || lang;
 
             return docsUrl.replace('/en/', '/' + lang + '/');
         } catch (error) {