EnforcedResponse.php

<?php

namespace Drupal\Core\Form;

use Symfony\Component\HttpFoundation\Response;

/**
 * A wrapper containing a response which is to be enforced upon delivery.
 *
 * The FormBuilder throws an EnforcedResponseException whenever a form
 * desires to explicitly set a response object. Exception handlers capable of
 * setting the response should extract the response object of such an exception
 * using EnforcedResponse::createFromException(). Then wrap it into an
 * EnforcedResponse object and replace the original response with the wrapped
 * response.
 *
 * @see Drupal\Core\EventSubscriber\EnforcedFormResponseSubscriber::onKernelException()
 * @see Drupal\Core\EventSubscriber\DefaultExceptionSubscriber::createHtmlResponse()
 * @see Drupal\Core\EventSubscriber\DefaultExceptionHtmlSubscriber::createResponse()
 */
class EnforcedResponse extends Response {
    
    /**
     * The wrapped response object.
     *
     * @var \Symfony\Component\HttpFoundation\Response
     */
    protected $response;
    
    /**
     * Constructs a new enforced response from the given exception.
     *
     * Note that it is necessary to traverse the exception chain when searching
     * for an enforced response. Otherwise it would be impossible to find an
     * exception thrown from within a twig template.
     *
     * @param \Throwable $e
     *   The exception where the enforced response is to be extracted from.
     *
     * @return static|null
     *   The enforced response or NULL if the exception chain does not contain a
     *   \Drupal\Core\Form\EnforcedResponseException exception.
     */
    public static function createFromException(\Throwable $e) {
        while ($e) {
            if ($e instanceof EnforcedResponseException) {
                return new static($e->getResponse());
            }
            $e = $e->getPrevious();
        }
    }
    
    /**
     * Constructs an enforced response.
     *
     * Use EnforcedResponse::createFromException() instead.
     *
     * @param \Symfony\Component\HttpFoundation\Response $response
     *   The response to wrap.
     */
    public function __construct(Response $response) {
        parent::__construct('', 500);
        $this->response = $response;
    }
    
    /**
     * Returns the wrapped response.
     *
     * @return \Symfony\Component\HttpFoundation\Response
     *   The wrapped response.
     */
    public function getResponse() {
        return $this->response;
    }

}