NodeViewBuilder.php

<?php

namespace Drupal\node;

use Drupal\Core\Entity\EntityInterface;
use Drupal\Core\Entity\EntityViewBuilder;
use Drupal\Core\Render\Element\Link;
use Drupal\Core\Security\TrustedCallbackInterface;

/**
 * View builder handler for nodes.
 */
class NodeViewBuilder extends EntityViewBuilder implements TrustedCallbackInterface {
    
    /**
     * {@inheritdoc}
     */
    public function buildComponents(array &$build, array $entities, array $displays, $view_mode) {
        
        /** @var \Drupal\node\NodeInterface[] $entities */
        if (empty($entities)) {
            return;
        }
        parent::buildComponents($build, $entities, $displays, $view_mode);
        foreach ($entities as $id => $entity) {
            $bundle = $entity->bundle();
            $display = $displays[$bundle];
            if ($display->getComponent('links')) {
                $build[$id]['links'] = [
                    '#lazy_builder' => [
                        static::class . '::renderLinks',
                        [
                            $entity->id(),
                            $view_mode,
                            $entity->language()
                                ->getId(),
                            !empty($entity->in_preview),
                            $entity->isDefaultRevision() ? NULL : $entity->getLoadedRevisionId(),
                        ],
                    ],
                ];
            }
            // Add Language field text element to node render array.
            if ($display->getComponent('langcode')) {
                $build[$id]['langcode'] = [
                    '#type' => 'item',
                    '#title' => t('Language'),
                    '#markup' => $entity->language()
                        ->getName(),
                    '#prefix' => '<div id="field-language-display">',
                    '#suffix' => '</div>',
                ];
            }
        }
    }
    
    /**
     * {@inheritdoc}
     */
    protected function getBuildDefaults(EntityInterface $entity, $view_mode) {
        $defaults = parent::getBuildDefaults($entity, $view_mode);
        // Don't cache nodes that are in 'preview' mode.
        if (isset($defaults['#cache']) && isset($entity->in_preview)) {
            unset($defaults['#cache']);
        }
        return $defaults;
    }
    
    /**
     * #lazy_builder callback; builds a node's links.
     *
     * @param string $node_entity_id
     *   The node entity ID.
     * @param string $view_mode
     *   The view mode in which the node entity is being viewed.
     * @param string $langcode
     *   The language in which the node entity is being viewed.
     * @param bool $is_in_preview
     *   Whether the node is currently being previewed.
     * @param $revision_id
     *   (optional) The identifier of the node revision to be loaded. If none
     *   is provided, the default revision will be loaded.
     *
     * @return array
     *   A renderable array representing the node links.
     */
    public static function renderLinks($node_entity_id, $view_mode, $langcode, $is_in_preview, $revision_id = NULL) {
        $links = [
            '#theme' => 'links__node',
            '#pre_render' => [
                [
                    Link::class,
                    'preRenderLinks',
                ],
            ],
            '#attributes' => [
                'class' => [
                    'links',
                    'inline',
                ],
            ],
        ];
        if (!$is_in_preview) {
            $storage = \Drupal::entityTypeManager()->getStorage('node');
            
            /** @var \Drupal\node\NodeInterface $revision */
            $revision = !isset($revision_id) ? $storage->load($node_entity_id) : $storage->loadRevision($revision_id);
            $entity = $revision->getTranslation($langcode);
            $links['node'] = static::buildLinks($entity, $view_mode);
            // Allow other modules to alter the node links.
            $hook_context = [
                'view_mode' => $view_mode,
                'langcode' => $langcode,
            ];
            \Drupal::moduleHandler()->alter('node_links', $links, $entity, $hook_context);
        }
        return $links;
    }
    
    /**
     * Build the default links (Read more) for a node.
     *
     * @param \Drupal\node\NodeInterface $entity
     *   The node object.
     * @param string $view_mode
     *   A view mode identifier.
     *
     * @return array
     *   An array that can be processed by Link::preRenderLinks().
     *
     * @see \Drupal\Core\Render\Element\Link::preRenderLinks()
     */
    protected static function buildLinks(NodeInterface $entity, $view_mode) {
        $links = [];
        // Always display a read more link on teasers because we have no way
        // to know when a teaser view is different than a full view.
        if ($view_mode == 'teaser') {
            $node_title_stripped = strip_tags($entity->label());
            $links['node-readmore'] = [
                'title' => t('Read more<span class="visually-hidden"> about @title</span>', [
                    '@title' => $node_title_stripped,
                ]),
                'url' => $entity->toUrl(),
                'language' => $entity->language(),
                'attributes' => [
                    'rel' => 'tag',
                    'title' => $node_title_stripped,
                ],
            ];
        }
        return [
            '#theme' => 'links__node__node',
            '#links' => $links,
            '#attributes' => [
                'class' => [
                    'links',
                    'inline',
                ],
            ],
        ];
    }
    
    /**
     * {@inheritdoc}
     */
    public static function trustedCallbacks() {
        $callbacks = parent::trustedCallbacks();
        $callbacks[] = 'renderLinks';
        return $callbacks;
    }

}