getSourceFieldConstraints example

  public function validate() {
    $media_source = $this->getSource();

    if ($media_source instanceof MediaSourceEntityConstraintsInterface) {
      $entity_constraints = $media_source->getEntityConstraints();
      $this->getTypedData()->getDataDefinition()->setConstraints($entity_constraints);
    }

    if ($media_source instanceof MediaSourceFieldConstraintsInterface) {
      $source_field_name = $media_source->getConfiguration()['source_field'];
      $source_field_constraints = $media_source->getSourceFieldConstraints();
      $this->get($source_field_name)->getDataDefinition()->setConstraints($source_field_constraints);
    }

    return parent::validate();
  }

  /** * {@inheritdoc} */
  public static function baseFieldDefinitions(EntityTypeInterface $entity_type) {
    $fields = parent::baseFieldDefinitions($entity_type);