How do I redirect users to an external URL?

Question

I implemented a controller class in Drupal 8, which redirects to an external site. If I use \Symfony\Component\HttpFoundation\RedirectResponse, I get this error.

Redirects to external URLs are not allowed by default, use \Drupal\Core\Routing\TrustedRedirectResponse for it.

Using \Drupal\Core\Routing\TrustedRedirectResponse, I get this error.

The controller result claims to be providing relevant cache metadata, but leaked metadata was detected. Please ensure you are not rendering content too early.
Returned object class: \Drupal\Core\Routing\TrustedRedirectResponse

What should I do?

Answer 1

Define a controller and redirect to external URL.

Use TrustedRedirectResponse class in case you know that you want to redirect to an external URL. Example below:

use Drupal\Core\Controller\ControllerBase; 
use Drupal\Core\Routing\TrustedRedirectResponse; 
class ExampleController extends ControllerBase {

  public function example() {
    return new TrustedRedirectResponse('https://google.com');  
  }
}

Answer 2

With a route name on a Controller:

use Drupal\Core\Controller\ControllerBase;
use Drupal\Core\Routing\TrustedRedirectResponse;
class MyControllerClass extends ControllerBase {

  public function foo() {
    //...
    return $this->redirect('user.page');
  }
}

With a absolute url:

return new RedirectResponse('https://google.com');

Answer 3

Alternatively implement hook_redirect_response_alter() (as per #2909182 patch).

Here is the example from redirect_test.module:

use Drupal\redirect\Entity\Redirect;
use Symfony\Component\HttpFoundation\RedirectResponse;

/**
 * Implements hook_redirect_response_alter().
 */
function redirect_test_redirect_response_alter(RedirectResponse $response, Redirect $redirect) {
  $path = 'test/redirect/2/successful';
  $replace = 'test/redirect/other';
  if ($redirect->getRedirect()['uri'] == "internal:/" . $path) {
    $response->setTargetUrl(str_replace($path, $replace, $redirect->getRedirectUrl()->setAbsolute()->toString()));
  }
}