aggregator-2.x-dev/tests/modules/aggregator_display_configurable_test/aggregator_display_configurable_test.module

<?php

/**
 * @file
 * A module for testing when aggregator_feed base fields' displays configurable.
 */

use Drupal\Core\Entity\EntityTypeInterface;

/**
 * Implements hook_entity_base_field_info_alter().
 */
function aggregator_display_configurable_test_entity_base_field_info_alter(&$base_field_definitions, EntityTypeInterface $entity_type) {
  /** @var \Drupal\Core\Field\BaseFieldDefinition[] $base_field_definitions */

  if ($entity_type->id() === 'aggregator_feed') {
    $base_field_definitions['title']->setDisplayConfigurable('view', TRUE);
    $base_field_definitions['description']->setDisplayConfigurable('view', TRUE);
    $base_field_definitions['image']->setDisplayConfigurable('view', TRUE);
  }

  if ($entity_type->id() === 'aggregator_item') {
    $base_field_definitions['title']->setDisplayConfigurable('view', TRUE);
    $options = [
      'type' => 'text_default',
      'label' => 'above',
    ];
    $base_field_definitions['title']->setDisplayOptions('view', $options);
  }
}

/**
 * Implements hook_entity_type_build().
 */
function aggregator_display_configurable_test_entity_type_build(array &$entity_types) {
  // Allow skipping of extra preprocessing for configurable display.
  $entity_types['aggregator_feed']->set('enable_base_field_custom_preprocess_skipping', TRUE);
  $entity_types['aggregator_item']->set('enable_base_field_custom_preprocess_skipping', TRUE);
}