wp_get_current_user does not work properly on log in page

Question

Desired Outcome

I am developing a plugin that should redirect the user away from log in page if they are already logged in.

So if anyone goes to example.com/wp-login.php and they are already logged in, the redirect should kick in.

Current Progress

I am using login_init hook to determine that we are in the log in page and wp_get_current_user() to get the user.

function redirect_logged_in_users() {
   if (is_user_logged_in()) {
     wp_redirect($destination);
  }
}

add_action('login_init', 'redirect_logged_in_users');

The Problem

This works well in any other page using some other hook, like init, but whenever I try this with login_init the wp_get_current_user() returns an empty user as if no one is logged in.

I know that there's a user logged in.

Additional Context

I am not a WordPress dev and I am almost sure that I am doing something in a non-WordPress way. Happy to take any other approach which helps to achieve the goal.

Answer 1

You have a chicken and egg problem going. login_init is called PRIOR to the user actually logged in. It just indicates with the login page has been displayed. (https://developer.wordpress.org/reference/hooks/login_init/)

The hook should be: wp_login. This fires after a user has successfully logged-in.
https://developer.wordpress.org/reference/hooks/wp_login/

add_action('wp_login', 'redirect_logged_in_users');