TestWaitTerminateMiddleware.php

<?php

namespace Drupal\Core\Test\StackMiddleware;

use Drupal\Core\Lock\LockBackendInterface;
use Drupal\Core\State\StateInterface;
use Symfony\Component\HttpFoundation\Request;
use Symfony\Component\HttpFoundation\Response;
use Symfony\Component\HttpKernel\HttpKernelInterface;

/**
 * Acquire a lock to signal request termination to the test runner.
 */
class TestWaitTerminateMiddleware implements HttpKernelInterface {
  
  /**
   * Constructs a test wait terminate stack middleware object.
   *
   * @param \Symfony\Component\HttpKernel\HttpKernelInterface $httpKernel
   *   The decorated kernel.
   * @param \Drupal\Core\State\StateInterface $state
   *   The state server.
   * @param \Drupal\Core\Lock\LockBackendInterface $lock
   *   The lock backend.
   */
  public function __construct(protected HttpKernelInterface $httpKernel, protected StateInterface $state, protected LockBackendInterface $lock) {
  }
  
  /**
   * {@inheritdoc}
   */
  public function handle(Request $request, $type = self::MAIN_REQUEST, $catch = TRUE) : Response {
    $result = $this->httpKernel
      ->handle($request, $type, $catch);
    if ($this->state
      ->get('drupal.test_wait_terminate')) {
      // Set a header on the response to instruct the test runner that it must
      // await the lock. Note that the lock acquired here is automatically
      // released from within a shutdown function.
      $this->lock
        ->acquire('test_wait_terminate');
      $result->headers
        ->set('X-Drupal-Wait-Terminate', '1');
    }
    return $result;
  }

}