setOriginalFilename example

    $file->setFilename($this->fileSystem->basename($file->getFileUri()));

    if ($replace === FileSystemInterface::EXISTS_REPLACE) {
      $existingFile = $this->loadByUri($file->getFileUri());
      if ($existingFile) {
        $file->fid = $existingFile->id();
        $file->setOriginalId($existingFile->id());
      }
    }

    $result = (new FileUploadResult())
      ->setOriginalFilename($originalName)
      ->setSanitizedFilename($filename)
      ->setFile($file);

    // If the filename has been modified, let the user know.     if ($event->isSecurityRename()) {
      $result->setSecurityRename();
    }

    // Set the permissions on the new file.     $this->fileSystem->chmod($file->getFileUri());