Issue #3379885 by catch, Wim Leers: Use MessagesCommand in BigPipe to remove...

      - { name: placeholder_strategy, priority: 0 }

  big_pipe:

    class: Drupal\big_pipe\Render\BigPipe

    arguments: ['@renderer', '@session', '@request_stack', '@http_kernel', '@event_dispatcher', '@config.factory']

    arguments: ['@renderer', '@session', '@request_stack', '@http_kernel', '@event_dispatcher', '@config.factory', '@messenger']

  Drupal\big_pipe\Render\BigPipe: '@big_pipe'

  html_response.attachments_processor.big_pipe:

    public: false

use Drupal\Component\Utility\Crypt;

use Drupal\Component\Utility\Html;

use Drupal\Core\Ajax\AjaxResponse;

use Drupal\Core\Ajax\MessageCommand;

use Drupal\Core\Ajax\ReplaceCommand;

use Drupal\Core\Asset\AttachedAssets;

use Drupal\Core\Asset\AttachedAssetsInterface;

use Drupal\Core\Config\ConfigFactoryInterface;

use Drupal\Core\Messenger\MessengerInterface;

use Drupal\Core\Render\HtmlResponse;

use Drupal\Core\Render\RendererInterface;

use Symfony\Contracts\EventDispatcher\EventDispatcherInterface;

   */

  protected $configFactory;

  /**

   * Constructs a new BigPipe class.

   *

   * @param \Drupal\Core\Render\RendererInterface $renderer

   *   The renderer.

   * @param \Symfony\Component\HttpFoundation\Session\SessionInterface $session

   *   The session.

   * @param \Symfony\Component\HttpFoundation\RequestStack $request_stack

   *   The request stack.

   * @param \Symfony\Component\HttpKernel\HttpKernelInterface $http_kernel

   *   The HTTP kernel.

   * @param \Symfony\Contracts\EventDispatcher\EventDispatcherInterface $event_dispatcher

   *   The event dispatcher.

   * @param \Drupal\Core\Config\ConfigFactoryInterface $config_factory

   *   The config factory.

   */

  public function __construct(RendererInterface $renderer, SessionInterface $session, RequestStack $request_stack, HttpKernelInterface $http_kernel, EventDispatcherInterface $event_dispatcher, ConfigFactoryInterface $config_factory) {

  public function __construct(RendererInterface $renderer, SessionInterface $session, RequestStack $request_stack, HttpKernelInterface $http_kernel, EventDispatcherInterface $event_dispatcher, ConfigFactoryInterface $config_factory, protected ?MessengerInterface $messenger = NULL) {

    $this->renderer = $renderer;

    $this->session = $session;

    $this->requestStack = $request_stack;

    $this->httpKernel = $http_kernel;

    $this->eventDispatcher = $event_dispatcher;

    $this->configFactory = $config_factory;

    if (!isset($this->messenger)) {

      @trigger_error('Calling ' . __CLASS__ . '::_construct() without the $messenger argument is deprecated in drupal:10.3.0 and it will be required in drupal:11.0.0. See https://www.drupal.org/node/3343754', E_USER_DEPRECATED);

      $this->messenger = \Drupal::messenger();

    }

  }

  /**

    // Create a Fiber for each placeholder.

    $fibers = [];

    $message_placeholder_id = NULL;

    foreach ($placeholder_order as $placeholder_id) {

      if (!isset($placeholders[$placeholder_id])) {

        continue;

      }

      $placeholder_render_array = $placeholders[$placeholder_id];

      // Ensure the messages placeholder renders last, the render order of every

      // other placeholder is safe to change.

      // @see static::getPlaceholderOrder()

      if (isset($placeholder_render_array['#lazy_builder']) && $placeholder_render_array['#lazy_builder'][0] === 'Drupal\Core\Render\Element\StatusMessages::renderMessages') {

        $message_placeholder_id = $placeholder_id;

      }

      $fibers[$placeholder_id] = new \Fiber(fn() => $this->renderPlaceholder($placeholder_id, $placeholder_render_array));

    }

    $iterations = 0;

    while (count($fibers) > 0) {

      foreach ($fibers as $placeholder_id => $fiber) {

        // Keep skipping the messages placeholder until it's the only Fiber

        // remaining. @todo https://www.drupal.org/project/drupal/issues/3379885

        if (isset($message_placeholder_id) && $placeholder_id === $message_placeholder_id && count($fibers) > 1) {

          continue;

        }

        try {

          if (!$fiber->isStarted()) {

            $fiber->start();

          $ajax_response->addCommand(new ReplaceCommand(sprintf('[data-big-pipe-placeholder-id="%s"]', $big_pipe_js_placeholder_id), $elements['#markup']));

          $ajax_response->setAttachments($elements['#attached']);

          // Delete all messages that were generated during the rendering of this

          // placeholder, to render them in a BigPipe-optimized way.

          $messages = $this->messenger->deleteAll();

          foreach ($messages as $type => $type_messages) {

            foreach ($type_messages as $message) {

              $ajax_response->addCommand(new MessageCommand($message, NULL, ['type' => $type], FALSE));

            }

          }

          // Push a fake request with the asset libraries loaded so far and

          // dispatch KernelEvents::RESPONSE event. This results in the

          // attachments for the AJAX response being processed by

   *

   * @return array

   *   Indexed array; the order in which the BigPipe placeholders will start

   *   execution. Placeholders begin execution in DOM order, except for the

   *   messages placeholder which must always be executed last. Note that due to

   *   execution. Placeholders begin execution in DOM order. Note that due to

   *   the Fibers implementation of BigPipe, although placeholders will start

   *   executing in DOM order, they may finish and render in any order. Values

   *   are the BigPipe placeholder IDs. Note that only unique placeholders are

    foreach ($xpath->query('//span[@data-big-pipe-placeholder-id]') as $node) {

      $placeholder_ids[] = Html::escape($node->getAttribute('data-big-pipe-placeholder-id'));

    }

    $placeholder_ids = array_unique($placeholder_ids);

    // The 'status messages' placeholder needs to be special cased, because it

    // depends on global state that can be modified when other placeholders are

    // being rendered: any code can add messages to render.

    // This violates the principle that each lazy builder must be able to render

    // itself in isolation, and therefore in any order. However, we cannot

    // change the way \Drupal\Core\Messenger\MessengerInterface::addMessage()

    // works in the Drupal 8 cycle. So we have to accommodate its special needs.

    // Allowing placeholders to be rendered in a particular order (in this case:

    // last) would violate this isolation principle. Thus a monopoly is granted

    // to this one special case, with this hard-coded solution.

    // @see \Drupal\Core\Render\Element\StatusMessages

    // @see \Drupal\Core\Render\Renderer::replacePlaceholders()

    // @see https://www.drupal.org/node/2712935#comment-11368923

    $message_placeholder_ids = [];

    foreach ($placeholders as $placeholder_id => $placeholder_element) {

      if (isset($placeholder_element['#lazy_builder']) && $placeholder_element['#lazy_builder'][0] === 'Drupal\Core\Render\Element\StatusMessages::renderMessages') {

        $message_placeholder_ids[] = $placeholder_id;

      }

    }

    // Return placeholder IDs in DOM order, but with the 'status messages'

    // placeholders at the end, if they are present.

    $ordered_placeholder_ids = array_merge(

      array_diff($placeholder_ids, $message_placeholder_ids),

      array_intersect($placeholder_ids, $message_placeholder_ids)

    );

    return $ordered_placeholder_ids;

    return array_unique($placeholder_ids);

  }

  /**

      $cases['exception__lazy_builder']->bigPipePlaceholderId          => NULL,

      $cases['exception__embedded_response']->bigPipePlaceholderId     => NULL,

    ], [

      0 => $cases['edge_case__html_non_lazy_builder']->bigPipePlaceholderId,

      0 => $cases['html']->bigPipePlaceholderId,

      1 => $cases['edge_case__html_non_lazy_builder']->bigPipePlaceholderId,

      // The suspended placeholder is replaced after the non-suspended

      // placeholder even though it appears first in the page.

      // @see Drupal\big_pipe\Render\BigPipe\Render::sendPlaceholders()

      1 => $cases['edge_case__html_non_lazy_builder_suspend']->bigPipePlaceholderId,

       // The 'html' case contains the 'status messages' placeholder, which is

      // always rendered last.

      2 => $cases['html']->bigPipePlaceholderId,

      2 => $cases['edge_case__html_non_lazy_builder_suspend']->bigPipePlaceholderId,

    ]);

    $this->assertSession()->responseContains('</body>');

    $this->assertTrue($this->container->get('module_installer')->install(['render_placeholder_message_test'], TRUE), 'Installed modules.');

    $this->drupalLogin($this->drupalCreateUser());

    $messages_markup = '<div role="contentinfo" aria-label="Status message"';

    $messages_markup = '<div class="messages messages--status" role="status"';

    $test_routes = [

      // Messages placeholder rendered first.

      'render_placeholder_message_test.first',

      $assert->elementContains('css', 'p.logged-message:nth-of-type(1)', 'Message: P1');

      $assert->elementContains('css', 'p.logged-message:nth-of-type(2)', 'Message: P2');

      $assert->responseContains($messages_markup);

      $assert->elementExists('css', 'div[aria-label="Status message"] ul');

      $assert->elementContains('css', 'div[aria-label="Status message"] ul li:nth-of-type(1)', 'P1');

      $assert->elementContains('css', 'div[aria-label="Status message"] ul li:nth-of-type(2)', 'P2');

      $assert->elementExists('css', 'div[aria-label="Status message"]');

      $assert->responseContains('aria-label="Status message">P1');

      $assert->responseContains('aria-label="Status message">P2');

      // Verify that we end with all messages printed, hence again zero queued.

      $this->drupalGet(Url::fromRoute('render_placeholder_message_test.queued'));

use Drupal\big_pipe\Render\BigPipe;

use Drupal\big_pipe\Render\BigPipeResponse;

use Drupal\Core\Config\ConfigFactoryInterface;

use Drupal\Core\Messenger\MessengerInterface;

use Drupal\Core\Render\ElementInfoManagerInterface;

use Drupal\Core\Render\HtmlResponse;

use Drupal\Core\Render\PlaceholderGeneratorInterface;

          'languages:language_interface',

          'theme',

        ],

      ]

      ],

    );

    $session = $this->prophesize(SessionInterface::class);

      $this->prophesize(HttpKernelInterface::class)->reveal(),

      $this->createMock(EventDispatcherInterface::class),

      $this->prophesize(ConfigFactoryInterface::class)->reveal(),

      $this->prophesize(MessengerInterface::class)->reveal(),

    );

    $response = new BigPipeResponse(new HtmlResponse());