Show field list in an autocomplete

src/Controller/FieldList.php

@@ -0,0 +1,34 @@
+<?php
+
+namespace Drupal\uceap_logging\Controller;
+
+use Drupal\Core\Controller\ControllerBase;
+use Symfony\Component\HttpFoundation\JsonResponse;
+use Symfony\Component\HttpFoundation\Request;
+use Drupal\field\Entity\FieldStorageConfig;
+
+class FieldList extends ControllerBase {
+
+  public function autocomplete(Request $request) {
+    $string = $request->query->get('q');
+
+    $fields = \Drupal::entityTypeManager()
+      ->getStorage('field_storage_config')
+      ->loadMultiple();
+
+    $matches = [];
+
+    foreach ($fields as $field) {
+      $name = $field->getName();
+
+      if (stripos($name, $string) !== FALSE) {
+        $matches[] = [
+          'value' => $name,
+          'label' => $name,
+        ];
+      }
+    }
+
+    return new JsonResponse($matches);
+  }
+}

src/Form/LoggingSettingsForm.php

@@ -4,6 +4,7 @@
 
 use Drupal\Core\Form\ConfigFormBase;
 use Drupal\Core\Form\FormStateInterface;
+use Drupal\field\Entity\FieldStorageConfig;
 
 /**
  * Configure UCEAP Logging settings.
@@ -31,11 +32,11 @@ public function buildForm(array $form, FormStateInterface $form_state) {
     $config = $this->config('uceap_logging.settings');
 
     $form['sensitive_fields'] = [
-      '#type' => 'textarea',
-      '#title' => $this->t('Sensitive Fields'),
-      '#description' => $this->t('Enter field machine names (one per line) that should have their values masked in entity change logs. When these fields are modified, they will appear in logs with masked values (e.g., ***MASKED***) instead of actual values.'),
-      '#default_value' => implode("\n", $config->get('sensitive_fields') ?? []),
-      '#rows' => 10,
+      '#type' => 'textfield',
+      '#title' => $this->t('Select Field Machine Name'),
+      '#autocomplete_route_name' => 'uceap_logging.field_list',
+      '#multiple' => TRUE,
+      '#default_value' => implode(', ', $config->get('sensitive_fields')) ?? [],
     ];
 
     $form['help'] = [
@@ -63,17 +64,10 @@ public function buildForm(array $form, FormStateInterface $form_state) {
    * {@inheritdoc}
    */
   public function submitForm(array &$form, FormStateInterface $form_state) {
-    // Convert textarea input to array.
-    $sensitive_fields_raw = $form_state->getValue('sensitive_fields');
-    $sensitive_fields = array_filter(
-      array_map('trim', explode("\n", $sensitive_fields_raw)),
-      function ($field) {
-        return !empty($field);
-      }
-    );
+    $selectable_sensitive_fields_raw = explode(",", $form_state->getValue('sensitive_fields'));
 
     $this->config('uceap_logging.settings')
-      ->set('sensitive_fields', array_values($sensitive_fields))
+      ->set('sensitive_fields', array_values($selectable_sensitive_fields_raw))
       ->save();
 
     parent::submitForm($form, $form_state);

uceap_logging.routing.yml

@@ -5,3 +5,10 @@ uceap_logging.settings:
     _title: 'Logging Settings'
   requirements:
     _permission: 'administer site configuration'
+
+uceap_logging.field_list:
+  path: '/field-list'
+  defaults:
+    _controller: '\Drupal\uceap_logging\Controller\FieldList::autocomplete'
+  requirements:
+    _permission: 'access content'