Dispatch failed authentication event in callback

+++ b/src/Controller/FacebookAuthController.php
@@ -62,12 +63,22 @@ class FacebookAuthController extends OAuth2ControllerBase {
+    $redirect = 'user.login';
+    $redirect_param = [];
+
+    if ($error_dest = $this->dataHandler->get('login_error_destination')) {
+      $url = Url::fromUserInput($error_dest);
+      $redirect = $url->getRouteName();
+      $redirect_param = $url->getRouteParameters();
+      // Set current login_error_destination to null. so, it can be set again.
+      $this->dataHandler->set('login_error_destination', NULL);
+    }

Can we somehow include this logic in Social Auth itself? It would be applicable to all other modules as well.

because each social site has different way to notify error.

In case of error, I think we can just call a function defined in Social Auth which takes care of dispatching the event and providing the error information. It is up to the event subscriber to handle the different errors that the implementers might throw. See my last comment in the related issue.

I made some changes to make the code a bit simpler and pass the error to the event handler. Thank you! I hope this helps with your project!