SchemaListenerController.php

<?php

namespace Drupal\config_test;

use Drupal\Core\Config\ConfigFactoryInterface;
use Drupal\Core\Config\Schema\SchemaIncompleteException;
use Drupal\Core\Controller\ControllerBase;
use Symfony\Component\DependencyInjection\ContainerInterface;

/**
 * Controller for testing \Drupal\Core\Config\Development\ConfigSchemaChecker.
 */
class SchemaListenerController extends ControllerBase {
  
  /**
   * Constructs the SchemaListenerController object.
   *
   * @param \Drupal\Core\Config\ConfigFactoryInterface $config_factory
   *   The config factory.
   */
  public function __construct(ConfigFactoryInterface $config_factory) {
    $this->configFactory = $config_factory;
  }
  
  /**
   * {@inheritdoc}
   */
  public static function create(ContainerInterface $container) {
    return new static($container->get('config.factory'));
  }
  
  /**
   * Tests the BrowserTestBase tests can use strict schema checking.
   */
  public function test() {
    try {
      $this->configFactory
        ->getEditable('config_schema_test.schemaless')
        ->set('foo', 'bar')
        ->save();
    } catch (SchemaIncompleteException $e) {
      return [
        '#markup' => $e->getMessage(),
      ];
    }
  }

}