Put each entity type table into a details element on admin/config/regional/content-language

Closes #3210684

core/lib/Drupal/Core/Field/Plugin/Field/FieldType/EntityReferenceItem.php

@@ -10,6 +10,7 @@
 use Drupal\Core\Entity\FieldableEntityInterface;
 use Drupal\Core\Entity\TypedData\EntityDataDefinition;
 use Drupal\Core\Field\FieldDefinitionInterface;
+use Drupal\Core\Field\FieldException;
 use Drupal\Core\Field\FieldItemBase;
 use Drupal\Core\Field\FieldStorageDefinitionInterface;
 use Drupal\Core\Field\PreconfiguredFieldUiOptionsInterface;
@@ -67,6 +68,12 @@ public static function propertyDefinitions(FieldStorageDefinitionInterface $fiel
     $settings = $field_definition->getSettings();
     $target_type_info = \Drupal::entityTypeManager()->getDefinition($settings['target_type']);
 
+    // If the target entity type doesn't have an ID key, we cannot determine
+    // the target_id data type.
+    if (!$target_type_info->hasKey('id')) {
+      throw new FieldException('Entity type "' . $target_type_info->id() . '" has no ID key and cannot be targeted by entity reference field "' . $field_definition->getName() . '"');
+    }
+
     $target_id_data_type = 'string';
     if ($target_type_info->entityClassImplements(FieldableEntityInterface::class)) {
       $id_definition = \Drupal::service('entity_field.manager')->getBaseFieldDefinitions($settings['target_type'])[$target_type_info->getKey('id')];
@@ -356,13 +363,23 @@ public function storageSettingsForm(array &$form, FormStateInterface $form_state
     $element['target_type'] = [
       '#type' => 'select',
       '#title' => t('Type of item to reference'),
-      '#options' => \Drupal::service('entity_type.repository')->getEntityTypeLabels(TRUE),
       '#default_value' => $this->getSetting('target_type'),
       '#required' => TRUE,
       '#disabled' => $has_data,
       '#size' => 1,
     ];
 
+    // Only allow the field to target entity types that have an ID key. This
+    // is enforced in ::propertyDefinitions().
+    $entity_type_manager = \Drupal::entityTypeManager();
+    $filter = function (string $entity_type_id) use ($entity_type_manager): bool {
+      return $entity_type_manager->getDefinition($entity_type_id)
+        ->hasKey('id');
+    };
+    $options = \Drupal::service('entity_type.repository')->getEntityTypeLabels(TRUE);
+    foreach ($options as $group_name => $group) {
+      $element['target_type']['#options'][$group_name] = array_filter($group, $filter, ARRAY_FILTER_USE_KEY);
+    }
     return $element;
   }
 
@@ -618,8 +635,9 @@ public function getSettableOptions(AccountInterface $account = NULL) {
   }
 
   /**
-   * Render API callback: Processes the field settings form and allows access to
-   * the form state.
+   * Render API callback: Processes the field settings form.
+   *
+   * Allows access to the form state.
    *
    * @see static::fieldSettingsForm()
    */