eca-1.0.x-dev/modules/form/src/Plugin/ECA/Condition/FormFieldExists.php

<?php

namespace Drupal\eca_form\Plugin\ECA\Condition;

/**
 * Checks whether the current form contains a specific form field.
 *
 * @EcaCondition(
 *   id = "eca_form_field_exists",
 *   label = @Translation("Form field: exists"),
 *   description = @Translation("Looks up the current form structure whether a specified field exists."),
 *   eca_version_introduced = "1.0.0"
 * )
 */
class FormFieldExists extends FormFieldConditionBase {

  /**
   * Whether to use form field value filters or not.
   *
   * @var bool
   */
  protected bool $useFilters = FALSE;

  /**
   * {@inheritdoc}
   */
  public function evaluate(): bool {
    if (!$this->getCurrentFormState()) {
      return FALSE;
    }
    $field_name = trim((string) $this->tokenService->replace($this->configuration['field_name']));
    if ($field_name === '') {
      throw new \InvalidArgumentException('Cannot use an empty string as field name');
    }
    $this->configuration['field_name'] = $field_name;
    return $this->negationCheck(!empty($this->getTargetElement()));
  }

}