Add Searchable Entity Formatter.

src/Plugin/Field/FieldFormatter/SearchableEntityFormatter.php

@@ -0,0 +1,100 @@
+<?php
+
+namespace Drupal\advanced_search\Plugin\Field\FieldFormatter;
+
+use Drupal\Core\Entity\EntityInterface;
+use Drupal\Core\Field\FieldItemListInterface;
+use Drupal\Core\Field\Plugin\Field\FieldFormatter\EntityReferenceLabelFormatter;
+use Drupal\Core\Form\FormStateInterface;
+
+/**
+ * Plugin implementation of the 'searchable_entity_formatter' formatter.
+ *
+ * @FieldFormatter(
+ *   id = "searchable_entity_formatter",
+ *   label = @Translation("Searchable entity formatter"),
+ *   field_types = {
+ *     "entity_reference"
+ *   }
+ * )
+ */
+class SearchableEntityFormatter extends EntityReferenceLabelFormatter {
+
+  /**
+   * {@inheritdoc}
+   */
+  public static function defaultSettings() {
+    return [
+      'search_link' => 'search?f[0]',
+      'search_var' => 'all_subjects',
+      'search_term' => FALSE,
+    ] + parent::defaultSettings();
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function settingsForm(array $form, FormStateInterface $form_state) {
+    $elements['search_link'] = [
+      '#title' => t('Search base path'),
+      '#type' => 'textfield',
+      '#required' => TRUE,
+      '#default_value' => $this->getSetting('search_link'),
+    ];
+    $elements['search_var'] = [
+      '#title' => t('Search variable'),
+      '#type' => 'textfield',
+      '#required' => TRUE,
+      '#default_value' => $this->getSetting('search_var'),
+    ];
+    $elements['search_term'] = [
+      '#title' => t('Use label as search term'),
+      '#type' => 'checkbox',
+      '#default_value' => $this->getSetting('search_term'),
+    ];
+    return $elements;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function settingsSummary() {
+    $summary = [];
+    $summary[] = t('Search path: @search_link', ['@search_link' => $this->getSetting('search_link')]);
+    $summary[] = t('Variable: @search_var', ['@search_var' => $this->getSetting('search_var')]);
+    $summary[] = $this->getSetting('search_term') ? t('Use label as search term') : t('Use ID as search term');
+    return $summary;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function viewElements(FieldItemListInterface $items, $langcode) {
+    $par_elements = parent::viewElements($items, $langcode);
+    foreach ($this->getEntitiesToView($items, $langcode) as $delta => $entity) {
+      $search_var = $this->getSetting('search_var');
+      $search_term = $this->getSetting('search_term');
+
+      if ($search_term == TRUE) {
+        $param = $par_elements[$delta]['#title'];
+      }
+      else {
+        $param = $entity->id();
+      }
+
+      $url = \Drupal::service('facets.utility.url_generator')->getUrl([$search_var => [$param]]);
+
+      $par_elements[$delta]['#url'] = $url;
+
+    }
+    return $par_elements;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  protected function checkAccess(EntityInterface $entity) {
+    return $entity->access('view label', NULL, TRUE);
+  }
+
+}