Symfony 4.4 google captcha integration to login form using KarserRecaptcha3Bundle

LoginSubcriber.php

<?php

namespace App\EventSubscriber;

use App\Form\LoginType;
use Symfony\Component\EventDispatcher\EventSubscriberInterface;
use Symfony\Component\Form\FormFactoryInterface;
use Symfony\Component\HttpFoundation\RedirectResponse;
use Symfony\Component\HttpFoundation\Session\Flash\FlashBagInterface;
use Symfony\Component\HttpKernel\Event\RequestEvent;
use Symfony\Component\HttpKernel\KernelEvents;
use Symfony\Component\Security\Core\Security;


class LoginSubscriber implements EventSubscriberInterface
{
    /**
     * @var FormFactoryInterface
     */
    private $formFactory;

    /**
     * @var FlashBagInterface
     */
    private $flashBag;

    public function __construct(FlashBagInterface $flashBag, FormFactoryInterface $formFactory)
    {
        $this->formFactory = $formFactory;
        $this->flashBag = $flashBag;
    }

    /**
     * @return array
     */
    public static function getSubscribedEvents()
    {
        /**
         * You can add event subscriber on KernelEvents::REQUEST with priority 9.
         * because class Symfony\Bundle\SecurityBundle\Debug\TraceableFirewallListener(responsible for registering the events for symfony firewall) has priority 8.
         */
        return array(
            KernelEvents::REQUEST => ['onLogin', 9]
        );
    }

    /**
     * @param RequestEvent $event
     */
    public function onLogin(RequestEvent $event)
    {
        if ('public_login' !== $event->getRequest()->attributes->get('_route')) {
            return;
        }

        //form generation should be in the same way (createdNamed in this case) as in LoginController
        $loginForm = $this->formFactory->createNamed(null, LoginType::class);
        if (!$loginForm->has('captcha')) {
            return;
        }
        $loginForm->handleRequest($event->getRequest());

        if (!$loginForm->isSubmitted()) {
            return;
        }

        if (!$loginForm->get('captcha')->isValid()) {
            $errors = $loginForm->get('captcha')->getErrors();
            $message = count($errors) ? $errors[0]->getMessage() : 'Failed to pass robot test';
            $this->flashBag->add(
                'error',
                $message
            );
            $session = $event->getRequest()->getSession();
            $session->set(Security::LAST_USERNAME, $loginForm->get('_username')->getData());

            //to prevent request to call next event
            $event->setResponse(new RedirectResponse($event->getRequest()->getRequestUri()));
        }
    }
}

LoginType.php

<?php

namespace App\Form;

use Karser\Recaptcha3Bundle\Form\Recaptcha3Type;
use Karser\Recaptcha3Bundle\Validator\Constraints\Recaptcha3;
use Symfony\Component\Form\AbstractType;
use Symfony\Component\Form\Extension\Core\Type\CheckboxType;
use Symfony\Component\Form\Extension\Core\Type\EmailType;
use Symfony\Component\Form\Extension\Core\Type\PasswordType;
use Symfony\Component\Form\FormBuilderInterface;
use Symfony\Component\OptionsResolver\OptionsResolver;

class LoginType extends AbstractType
{

    public function buildForm(FormBuilderInterface $builder, array $options)
    {
        $builder
            ->add('_username', EmailType::class, ['attr' => ['placeholder' => 'email'], 'data' => $options['lastUsername']])
            ->add('_password', PasswordType::class, ['attr' => ['placeholder' => 'password']])
            ->add('_remember_me', CheckboxType::class, ['required' => false])
        ;
        $builder->add('captcha', Recaptcha3Type::class, [
            'constraints' => new Recaptcha3(),
            'action_name' => 'login'
        ]);
    }

    public function configureOptions(OptionsResolver $resolver)
    {
        $resolver->setDefaults([
            //default csrf parameters defined in Symfony codes. without this configuratio csrf check will fail
            'csrf_field_name' => '_csrf_token',
            'csrf_token_id'   => 'authenticate',
          
            'lastUsername' => null
        ]);
    }
}