EntityReferenceLabelFormatter.php

<?php

namespace Drupal\Core\Field\Plugin\Field\FieldFormatter;

use Drupal\Core\Cache\CacheableMetadata;
use Drupal\Core\Entity\EntityInterface;
use Drupal\Core\Entity\Exception\UndefinedLinkTemplateException;
use Drupal\Core\Field\Attribute\FieldFormatter;
use Drupal\Core\Field\FieldItemListInterface;
use Drupal\Core\Form\FormStateInterface;
use Drupal\Core\StringTranslation\TranslatableMarkup;

/**
 * Plugin implementation of the 'entity reference label' formatter.
 */
class EntityReferenceLabelFormatter extends EntityReferenceFormatterBase {
    
    /**
     * {@inheritdoc}
     */
    public static function defaultSettings() {
        return [
            'link' => TRUE,
        ] + parent::defaultSettings();
    }
    
    /**
     * {@inheritdoc}
     */
    public function settingsForm(array $form, FormStateInterface $form_state) {
        $elements['link'] = [
            '#title' => $this->t('Link label to the referenced entity'),
            '#type' => 'checkbox',
            '#default_value' => $this->getSetting('link'),
        ];
        return $elements;
    }
    
    /**
     * {@inheritdoc}
     */
    public function settingsSummary() {
        $summary = [];
        $summary[] = $this->getSetting('link') ? $this->t('Link to the referenced entity') : $this->t('No link');
        return $summary;
    }
    
    /**
     * {@inheritdoc}
     */
    public function viewElements(FieldItemListInterface $items, $langcode) {
        $elements = [];
        $output_as_link = $this->getSetting('link');
        foreach ($this->getEntitiesToView($items, $langcode) as $delta => $entity) {
            $elements[$delta] = [
                '#entity' => $entity,
            ];
            $label = $entity->label();
            $cacheability = CacheableMetadata::createFromObject($entity);
            // If the link is to be displayed and the entity has a uri, display a
            // link.
            if ($output_as_link && !$entity->isNew()) {
                try {
                    $uri = $entity->toUrl();
                } catch (UndefinedLinkTemplateException) {
                    // This exception is thrown by
                    // \Drupal\Core\Entity\EntityInterface::toUrl() and it means that the
                    // entity type doesn't have a link template nor a valid
                    // "uri_callback", so don't bother trying to output a link for the
                    // rest of the referenced entities.
                    $elements[$delta]['#plain_text'] = $label;
                    $cacheability->applyTo($elements[$delta]);
                    continue;
                }
                $uri_access = $uri->access(return_as_object: TRUE);
                $cacheability->addCacheableDependency($uri_access);
                if ($uri_access->isAllowed()) {
                    $elements[$delta] += [
                        '#type' => 'link',
                        '#title' => $label,
                        '#url' => $uri,
                        '#options' => $uri->getOptions(),
                    ];
                    if (!empty($items[$delta]->_attributes)) {
                        $elements[$delta]['#options'] += [
                            'attributes' => [],
                        ];
                        $elements[$delta]['#options']['attributes'] += $items[$delta]->_attributes;
                        // Unset field item attributes since they have been included in the
                        // formatter output and shouldn't be rendered in the field template.
                        unset($items[$delta]->_attributes);
                    }
                }
                else {
                    $elements[$delta]['#plain_text'] = $label;
                }
            }
            else {
                $elements[$delta]['#plain_text'] = $label;
            }
            $cacheability->applyTo($elements[$delta]);
        }
        return $elements;
    }
    
    /**
     * {@inheritdoc}
     */
    protected function checkAccess(EntityInterface $entity) {
        return $entity->access('view label', NULL, TRUE);
    }

}