Same name in other branches

1. 9 core/modules/big_pipe/src/Render/BigPipe.php \Drupal\big_pipe\Render\BigPipe::sendPlaceholders()
2. 8.9.x core/modules/big_pipe/src/Render/BigPipe.php \Drupal\big_pipe\Render\BigPipe::sendPlaceholders()
3. 11.x core/modules/big_pipe/src/Render/BigPipe.php \Drupal\big_pipe\Render\BigPipe::sendPlaceholders()

Sends BigPipe placeholders' replacements as embedded AJAX responses.

Parameters

array $placeholders: Associative array; the BigPipe placeholders. Keys are the BigPipe placeholder IDs.

array $placeholder_order: Indexed array; the order in which the BigPipe placeholders must be sent. Values are the BigPipe placeholder IDs. (These values correspond to keys in $placeholders.)

\Drupal\Core\Asset\AttachedAssetsInterface $cumulative_assets: The cumulative assets sent so far; to be updated while rendering BigPipe placeholders.

Throws

\Exception If an exception is thrown during the rendering of a placeholder, it is caught to allow the other placeholders to still be replaced. But when error logging is configured to be verbose, the exception is rethrown to simplify debugging.

1 call to BigPipe::sendPlaceholders()

BigPipe::sendContent in core/modules/big_pipe/src/Render/BigPipe.php

Sends an HTML response in chunks using the BigPipe technique.

File

core/modules/big_pipe/src/Render/BigPipe.php, line 498

Class

BigPipe

Service for sending an HTML response in chunks (to get faster page loads).

Namespace

Drupal\big_pipe\Render

Code

protected function sendPlaceholders(array $placeholders, array $placeholder_order, AttachedAssetsInterface $cumulative_assets) {
    // Return early if there are no BigPipe placeholders to send.
    if (empty($placeholders)) {
        return;
    }
    // Send the start signal.
    $this->sendChunk("\n" . static::START_SIGNAL . "\n");
    // A BigPipe response consists of an HTML response plus multiple embedded
    // AJAX responses. To process the attachments of those AJAX responses, we
    // need a fake request that is identical to the main request, but with
    // one change: it must have the right Accept header, otherwise the work-
    // around for a bug in IE9 will cause not JSON, but <textarea>-wrapped JSON
    // to be returned.
    // @see \Drupal\Core\EventSubscriber\AjaxResponseSubscriber::onResponse()
    $fake_request = $this->requestStack
        ->getMainRequest()
        ->duplicate();
    $fake_request->headers
        ->set('Accept', 'application/vnd.drupal-ajax');
    // Create a Fiber for each placeholder.
    $fibers = [];
    foreach ($placeholder_order as $placeholder_id) {
        if (!isset($placeholders[$placeholder_id])) {
            continue;
        }
        $placeholder_render_array = $placeholders[$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 => $fiber) {
            try {
                if (!$fiber->isStarted()) {
                    $fiber->start();
                }
                elseif ($fiber->isSuspended()) {
                    $fiber->resume();
                }
                // If the Fiber hasn't terminated by this point, move onto the next
                // placeholder, we'll resume this Fiber again when we get back here.
                if (!$fiber->isTerminated()) {
                    // If we've gone through the placeholders once already, and they're
                    // still not finished, then start to allow code higher up the stack
                    // to get on with something else.
                    if ($iterations) {
                        $fiber = \Fiber::getCurrent();
                        if ($fiber !== NULL) {
                            $fiber->suspend();
                        }
                    }
                    continue;
                }
                $elements = $fiber->getReturn();
                unset($fibers[$placeholder_id]);
                // Create a new AjaxResponse.
                $ajax_response = new AjaxResponse();
                // JavaScript's querySelector automatically decodes HTML entities in
                // attributes, so we must decode the entities of the current BigPipe
                // placeholder ID (which has HTML entities encoded since we use it to
                // find the placeholders).
                $big_pipe_js_placeholder_id = Html::decodeEntities($placeholder_id);
                $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
                // AjaxResponseAttachmentsProcessor and hence:
                // - the necessary AJAX commands to load the necessary missing asset
                //   libraries and updated AJAX page state are added to the AJAX
                //   response
                // - the attachments associated with the response are finalized,
                // which allows us to track the total set of asset libraries sent in
                // the initial HTML response plus all embedded AJAX responses sent so
                // far.
                $fake_request->query
                    ->set('ajax_page_state', [
                    'libraries' => implode(',', $cumulative_assets->getAlreadyLoadedLibraries()),
                ] + $cumulative_assets->getSettings()['ajaxPageState']);
                $ajax_response = $this->filterEmbeddedResponse($fake_request, $ajax_response);
                // Send this embedded AJAX response.
                $json = $ajax_response->getContent();
                $output = <<<EOF
<script type="application/vnd.drupal-ajax" data-big-pipe-replacement-for-placeholder-with-id="{<span class="php-variable">$placeholder_id</span>}">
{<span class="php-variable">$json</span>}
</script>
EOF;
                $this->sendChunk($output);
                // Another placeholder was rendered and sent, track the set of asset
                // libraries sent so far. Any new settings are already sent; we
                // don't need to track those.
                if (isset($ajax_response->getAttachments()['drupalSettings']['ajaxPageState']['libraries'])) {
                    $cumulative_assets->setAlreadyLoadedLibraries(explode(',', $ajax_response->getAttachments()['drupalSettings']['ajaxPageState']['libraries']));
                }
            } catch (\Exception $e) {
                unset($fibers[$placeholder_id]);
                if ($this->configFactory
                    ->get('system.logging')
                    ->get('error_level') === ERROR_REPORTING_DISPLAY_VERBOSE) {
                    throw $e;
                }
                else {
                    trigger_error($e, E_USER_ERROR);
                }
            }
        }
        $iterations++;
    }
    // Send the stop signal.
    $this->sendChunk("\n" . static::STOP_SIGNAL . "\n");
}

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