Issue #3000623: Implement pagination for autocomplete requests

js/select2.js

@@ -38,6 +38,7 @@
             }
             return $.extend({}, params, {
               q: params.term,
+              page: params.page || 1
               selected: selected.filter(function (selected) {
                 return !selected.startsWith('$ID:');
               })

src/Controller/EntityAutocompleteController.php

@@ -83,7 +83,20 @@ public function handleAutocomplete(Request $request, $target_type, $selection_ha
         // key/value store.
         throw new AccessDeniedHttpException();
       }
-      $matches['results'] = $this->matcher->getMatches($target_type, $selection_handler, $selection_settings, mb_strtolower($input), $request->query->get('selected', []));
+
+      $matches['results'] = $this->matcher->getMatches($target_type, $selection_handler, $selection_settings, mb_strtolower($input), $request->query->get('selected', []), $request->query->get('page') - 1);
+
+      // Remove reflection in Drupal 10.0.0.
+      $options = $selection_settings + [
+        'target_type' => $target_type,
+        'handler' => $selection_handler,
+      ];
+      $handler = \Drupal::service('plugin.manager.entity_reference_selection')->getInstance($options);
+      $method = new \ReflectionMethod($handler, 'getReferenceableEntities');
+      $parameters = $method->getParameters();
+      if (count($parameters) > 3 && $parameters[3]->getName() === 'offset') {
+        $matches['pagination']['more'] = count($matches['results']) == 10;
+      }
     }
 
     return new JsonResponse($matches);

src/EntityAutocompleteMatcher.php

@@ -51,6 +51,8 @@ public function __construct(SelectionPluginManagerInterface $selection_manager,
    *   (optional) The label of the entity to query by.
    * @param array $selected
    *   (optional) An array of already selected items.
+   * @param int $page
+   *   (optional) An offset for the results.
    *
    * @return array
    *   An array of matched entity labels, in the format required by the AJAX
@@ -61,7 +63,7 @@ public function __construct(SelectionPluginManagerInterface $selection_manager,
    *
    * @see \Drupal\system\Controller\EntityAutocompleteController
    */
-  public function getMatches($target_type, $selection_handler, array $selection_settings, $string = '', array $selected = []) {
+  public function getMatches($target_type, $selection_handler, array $selection_settings, $string = '', array $selected = [], $page = 0) {
     $matches = [];
 
     $options = $selection_settings + [
@@ -73,9 +75,10 @@ public function getMatches($target_type, $selection_handler, array $selection_se
     if (isset($string)) {
       // Get an array of matching entities.
       $match_operator = !empty($selection_settings['match_operator']) ? $selection_settings['match_operator'] : 'CONTAINS';
-      $match_limit = isset($selection_settings['match_limit']) ? (int) $selection_settings['match_limit'] : 10;
-      $entity_labels = $handler->getReferenceableEntities($string, $match_operator, $match_limit + count($selected));
 
+      $match_limit = isset($selection_settings['match_limit']) ? (int) $selection_settings['match_limit'] : 10;
+      $entity_labels = $handler->getReferenceableEntities($string, $match_operator, $match_limit + count($selected), $page * 10);
+
       // Loop through the entities and convert them into autocomplete output.
       foreach ($entity_labels as $values) {
         foreach ($values as $entity_id => $label) {