ParagraphsDemoUserToTextUser.php

<?php

namespace Drupal\paragraphs_demo\Plugin\paragraphs\Conversion;

use Drupal\paragraphs\ParagraphInterface;
use Drupal\paragraphs\ParagraphsConversionBase;

/**
 * Provides a Paragraphs conversion plugin.
 *
 * @ParagraphsConversion(
 *   id = "paragraphs_demo_user_to_text_user",
 *   label = @Translation("Convert to Text and User"),
 *   source_type = "user",
 *   target_types = {"text", "user"},
 *   weight = 0
 * )
 */
class ParagraphsDemoUserToTextUser extends ParagraphsConversionBase {

  /**
   * {@inheritdoc}
   */
  public function convert(array $settings, ParagraphInterface $original_paragraph, array $converted_paragraphs = NULL) {
    $username = "Empty user field";
    $user = NULL;
    if ($original_paragraph
      ->get('field_user_demo')->entity) {
      $username = $original_paragraph
        ->get('field_user_demo')->entity
        ->label();
      $user = $original_paragraph
        ->get('field_user_demo')->entity;
    }
    return [
      [
        'type' => 'text',
        'field_text_demo' => [
          'value' => $username,
        ],
      ],
      [
        'type' => 'user',
        'field_user_demo' => $user ?: NULL,
      ],
    ];
  }

}