drush_plugin__composer_check/ComposerCheck/RequirementsLoader.php

<?php

namespace Fgm\ComposerCheck;

/**
 * Class RequirementsLoader loads a composer.json file.
 */
class RequirementsLoader extends LoaderBase implements LoaderInterface {

  /**
   * {@inheritdoc}
   */
  public function __construct(string $directory) {
    $this->file = realpath("${directory}/composer.json");
  }

  /**
   * {@inheritdoc}
   */
  public function parse() {
    $this->run = $this->contents['require'] ?? [];
    $this->dev = $this->contents['require-dev'] ?? [];
  }

}