class AccessPolicyProcessorInFibersTest

class AccessPolicyProcessorInFibersTest extends KernelTestBase {
  use UserCreationTrait;
  
  /**
   * {@inheritdoc}
   */
  protected static $modules = [
    'system',
    'user',
  ];
  
  /**
   * Tests the behavior of the access policy processor running inside fibers.
   */
  public function testAccessPolicyProcessorInFibers() : void {
    // Create a role and then empty the static cache, so that it will need to be
    // loaded from storage.
    $this->createRole([
      'administer modules',
    ], 'test_role');
    \Drupal::entityTypeManager()->getStorage('user_role')
      ->resetCache();
    // Create a render array with two elements that have lazy builders. The
    // first lazy builder prints the ID of the current user. The second lazy
    // builder checks the permissions of a different user, which results in a
    // call to AccountPolicyProcessor::processAccessPolicies(). In that method,
    // if the current user ID is different from the ID of the account being
    // processed, the current user is temporarily switched to that account.
    // This is done in order to make sure the correct user's data is used when
    // saving to the variation cache.
    //
    // Note that for the purposes of this test, the lazy builder that accesses
    // the current user ID has to come before the other lazy builder in the
    // render array. Ordering the array this way results in the second lazy
    // builder starting to run before the first. This happens because as render
    // contexts are updated as they are bubbled, the BubbleableMetadata object
    // associated with the render element merges its attached placeholder to the
    // front of the list to be processed.
    $build = [
      [
        '#lazy_builder' => [
          self::class . '::lazyBuilderCheckCurrentUserCallback',
          [],
        ],
        '#create_placeholder' => TRUE,
      ],
      [
        // Add a space between placeholders.
'#markup' => ' ',
      ],
      [
        '#lazy_builder' => [
          self::class . '::lazyBuilderCheckAccessCallback',
          [],
        ],
        '#create_placeholder' => TRUE,
      ],
    ];
    $user2 = new UserSession([
      'uid' => 2,
    ]);
    $this->setCurrentUser($user2);
    $expected = 'The current user id is 2. User 3 can administer modules.';
    $output = (string) \Drupal::service(RendererInterface::class)->renderRoot($build);
    $this->assertSame($expected, $output);
  }
  
  /**
   * Lazy builder that displays the current user ID.
   */
  public static function lazyBuilderCheckCurrentUserCallback() : array {
    return [
      '#markup' => new FormattableMarkup('The current user id is @id.', [
        '@id' => \Drupal::currentUser()->id(),
      ]),
    ];
  }
  
  /**
   * Lazy builder that checks permissions on a different user.
   */
  public static function lazyBuilderCheckAccessCallback() : array {
    $user3 = new UserSession([
      'uid' => 3,
      'roles' => [
        'test_role' => 'test_role',
      ],
    ]);
    return [
      '#markup' => new FormattableMarkup('User @id can administer modules.', [
        '@id' => $user3->id(),
      ]),
      '#access' => $user3->hasPermission('administer modules'),
    ];
  }

}