class EntityWorkspaceConflictConstraintValidator

class EntityWorkspaceConflictConstraintValidator extends ConstraintValidator implements ContainerInjectionInterface {
  
  /**
   * The entity type manager.
   *
   * @var \Drupal\Core\Entity\EntityTypeManagerInterface
   */
  protected $entityTypeManager;
  
  /**
   * The workspace manager service.
   *
   * @var \Drupal\workspaces\WorkspaceManagerInterface
   */
  protected $workspaceManager;
  
  /**
   * The workspace association service.
   *
   * @var \Drupal\workspaces\WorkspaceAssociationInterface
   */
  protected $workspaceAssociation;
  
  /**
   * The workspace repository service.
   *
   * @var \Drupal\workspaces\WorkspaceRepositoryInterface
   */
  protected $workspaceRepository;
  
  /**
   * Constructs an EntityUntranslatableFieldsConstraintValidator object.
   *
   * @param \Drupal\Core\Entity\EntityTypeManagerInterface $entity_type_manager
   *   The entity type manager service.
   * @param \Drupal\workspaces\WorkspaceManagerInterface $workspace_manager
   *   The workspace manager service.
   * @param \Drupal\workspaces\WorkspaceAssociationInterface $workspace_association
   *   The workspace association service.
   * @param \Drupal\workspaces\WorkspaceRepositoryInterface $workspace_repository
   *   The Workspace repository service.
   */
  public function __construct(EntityTypeManagerInterface $entity_type_manager, WorkspaceManagerInterface $workspace_manager, WorkspaceAssociationInterface $workspace_association, WorkspaceRepositoryInterface $workspace_repository) {
    $this->entityTypeManager = $entity_type_manager;
    $this->workspaceManager = $workspace_manager;
    $this->workspaceAssociation = $workspace_association;
    $this->workspaceRepository = $workspace_repository;
  }
  
  /**
   * {@inheritdoc}
   */
  public static function create(ContainerInterface $container) {
    return new static($container->get('entity_type.manager'), $container->get('workspaces.manager'), $container->get('workspaces.association'), $container->get('workspaces.repository'));
  }
  
  /**
   * {@inheritdoc}
   */
  public function validate($entity, Constraint $constraint) {
    /** @var \Drupal\Core\Entity\EntityInterface $entity */
    if (isset($entity) && !$entity->isNew()) {
      $active_workspace = $this->workspaceManager
        ->getActiveWorkspace();
      // Get the latest revision of the entity in order to check if it's being
      // edited in a different workspace.
      $latest_revision = $this->workspaceManager
        ->executeOutsideWorkspace(function () use ($entity) {
        $storage = $this->entityTypeManager
          ->getStorage($entity->getEntityTypeId());
        return $storage->loadRevision($storage->getLatestRevisionId($entity->id()));
      });
      // If the latest revision of the entity is tracked in a workspace, it can
      // only be edited in that workspace or one of its descendants.
      if ($latest_revision_workspace = $latest_revision->workspace->entity) {
        $descendants_and_self = $this->workspaceRepository
          ->getDescendantsAndSelf($latest_revision_workspace->id());
        if (!$active_workspace || !in_array($active_workspace->id(), $descendants_and_self, TRUE)) {
          $this->context
            ->buildViolation($constraint->message)
            ->setParameter('%label', $latest_revision_workspace->label())
            ->addViolation();
        }
      }
    }
  }

}