bfix: handles error incase of unsuccessful logout

lib/services/user_config.dart

@@ -132,11 +132,11 @@ class UserConfig {
   /// **returns**:
   /// * `Future<bool>`: returns future of bool type.
   Future<bool> userLogOut() async {
+    bool isLogOutSuccessful = false;
     try {
       final result = await databaseFunctions.gqlAuthMutation(queries.logout())
           as QueryResult?;
       if (result != null && result.data!['logout'] == true) {
-        navigationService.pop();
         navigationService.pushDialog(
           const CustomProgressDialog(
             key: Key('LogoutProgress'),
@@ -161,11 +161,12 @@ class UserConfig {
         // }
         await organisation.clear();
         _currentUser = User(id: 'null', authToken: 'null');
+        isLogOutSuccessful = true;
       }
     } catch (e) {
-      return false;
+      isLogOutSuccessful = false;
     }
-    return true;
+    return isLogOutSuccessful;
   }
 
   /// Updates the user joined organization.

lib/view_model/after_auth_view_models/settings_view_models/app_setting_view_model.dart

@@ -14,10 +14,11 @@ class AppSettingViewModel extends BaseModel {
   ///   None
   ///
   /// **returns**:
-  ///   None
-  Future<void> logout() async {
+  /// * `Future<bool>`: Logs the user out and returns the logout status as a [bool].
+  Future<bool> logout() async {
     // push custom alert dialog with the confirmation message.
-    await userConfig.userLogOut();
+    final bool isloggedOut = await userConfig.userLogOut();
+    return isloggedOut;
   }
 
   /// Launches a website using the provided URL.

lib/view_model/lang_view_model.dart

@@ -137,7 +137,7 @@ class AppLanguage extends BaseModel {
   /// **returns**:
   ///   None
   Future<void> selectLanguagePress() async {
-    if (userConfig.loggedIn) {
+    if (userConfig.currentUser.id != 'null') {
       dbLanguageUpdate();
       navigationService.popAndPushScreen('/appSettingsPage', arguments: '');
     } else {

lib/views/after_auth_screens/app_settings/app_settings_page.dart

@@ -302,11 +302,16 @@ class AppSettingsPage extends StatelessWidget {
                         successText: 'LogOut',
                         success: () async {
                           try {
-                            await model.logout();
+                            final bool isLogoutSuccessful =
+                                await model.logout();
+                            if (!isLogoutSuccessful) {
+                              throw Error(); //checks whether the logout was successful or not.
+                            }
                             navigationService.pop();
                             navigationService.removeAllAndPush(
-                              '/selectLang',
-                              '/',
+                              Routes.setUrlScreen,
+                              Routes.splashScreen,
+                              arguments: '',
                             );
                           } catch (e) {
                             navigationService.pushDialog(

test/service_tests/user_config_test.dart

@@ -197,7 +197,6 @@ void main() async {
 
       expect(loggedOut, true);
 
-      verify(navigationService.pop());
       expect(userBox.isEmpty, true);
       expect(urlBox.isEmpty, true);
       expect(orgBox.isEmpty, true);

test/view_model_tests/lang_view_model_test.dart

@@ -7,6 +7,7 @@ import 'package:mockito/mockito.dart';
 import 'package:shared_preferences/shared_preferences.dart';
 import 'package:talawa/constants/routing_constants.dart';
 import 'package:talawa/models/mainscreen_navigation_args.dart';
+import 'package:talawa/models/user/user_info.dart';
 import 'package:talawa/services/graphql_config.dart';
 import 'package:talawa/view_model/lang_view_model.dart';
 
@@ -100,7 +101,7 @@ void main() {
       await model.initialize();
 
       // consider if user is not logged in.
-      when(userConfig.loggedIn).thenReturn(false);
+      when(userConfig.currentUser).thenReturn(User(id: 'null'));
 
       when(
         navigationService.pushScreen(
@@ -126,7 +127,7 @@ void main() {
       );
 
       // consider if user is logged in.
-      when(userConfig.loggedIn).thenReturn(true);
+      when(userConfig.currentUser).thenReturn(User(id: 'xyz1'));
 
       when(
         navigationService.popAndPushScreen(

test/widget_tests/after_auth_screens/app_settings/app_setting_page_test.dart

@@ -8,6 +8,7 @@ import 'package:mockito/mockito.dart';
 import 'package:provider/provider.dart';
 import 'package:talawa/constants/constants.dart';
 import 'package:talawa/constants/custom_theme.dart';
+import 'package:talawa/constants/routing_constants.dart';
 import 'package:talawa/models/language/language_model.dart';
 import 'package:talawa/router.dart' as router;
 import 'package:talawa/services/graphql_config.dart';
@@ -308,5 +309,28 @@ Future<void> main() async {
       final logoutButton = find.textContaining('LogOut');
       await tester.tap(logoutButton);
     });
+
+    testWidgets('Test if Logout is successful', (tester) async {
+      final model = AppSettingViewModel();
+      when(model.logout()).thenAnswer((_) async => true);
+
+      await tester.pumpWidget(createChangePassScreenDark());
+      await tester.pumpAndSettle();
+
+      await tester.tap(find.byKey(const Key('Logout')));
+      await tester.pumpAndSettle();
+
+      final logoutButton = find.textContaining('LogOut');
+      await tester.tap(logoutButton);
+
+      verify(navigationService.pop());
+      verify(
+        navigationService.removeAllAndPush(
+          Routes.setUrlScreen,
+          Routes.splashScreen,
+          arguments: '',
+        ),
+      );
+    });
   });
 }