HtmlResponse.php

<?php

namespace Drupal\Core\Render;

use Drupal\Core\Cache\CacheableMetadata;
use Drupal\Core\Cache\CacheableResponseInterface;
use Drupal\Core\Cache\CacheableResponseTrait;
use Symfony\Component\HttpFoundation\Response;

/**
 * A response that contains and can expose cacheability metadata and attachments.
 *
 * Supports Drupal's caching concepts: cache tags for invalidation and cache
 * contexts for variations.
 *
 * Supports Drupal's idea of #attached metadata: libraries, settings, http_header and html_head.
 *
 * @see \Drupal\Core\Cache\CacheableResponse
 * @see \Drupal\Core\Render\AttachmentsInterface
 * @see \Drupal\Core\Render\AttachmentsTrait
 */
class HtmlResponse extends Response implements CacheableResponseInterface, AttachmentsInterface {
    use CacheableResponseTrait;
    use AttachmentsTrait;
    
    /**
     * {@inheritdoc}
     */
    public function setContent($content) {
        // A render array can automatically be converted to a string and set the
        // necessary metadata.
        if (is_array($content) && isset($content['#markup'])) {
            $content += [
                '#attached' => [
                    'html_response_attachment_placeholders' => [],
                    'placeholders' => [],
                ],
            ];
            $this->addCacheableDependency(CacheableMetadata::createFromRenderArray($content));
            $this->setAttachments($content['#attached']);
            $content = $content['#markup'];
        }
        return parent::setContent($content);
    }

}