src/Controller/SecurityController.php at line 39

/*
 * The $user argument type (?User) must be nullable because the login page
 * must be accessible to anonymous visitors too.
 */
#[Route('/login', name: 'security_login')]
public function login(
    #[CurrentUser] ?User $user,
    Request $request,
    AuthenticationUtils $helper,
): Response {
    // if user is already logged in, don't display the login page again
    if ($user) {
        return $this->redirectToRoute('app_dashboard', [
            '_locale' => $request->getLocale(),
        ]);
    }

    // this statement solves an edge-case: if you change the locale in the login
    // page, after a successful login you are redirected to a page in the previous
    // locale. This code regenerates the referrer URL whenever the login page is
    // browsed, to ensure that its locale is always the current one.
    $this->saveTargetPath($request->getSession(), 'main', $this->generateUrl('homepage'));

    return $this->render('security/login.html.twig', [
        // last username entered by the user (if any)
        'last_username' => $helper->getLastUsername(),
        // last authentication error (if any)
        'error' => $helper->getLastAuthenticationError(),
    ]);
}