admin_ui-8.x-1.x-dev/modules/jsonapi_support/jsonapi_support.install

<?php

/**
 * @file
 * Install, update and uninstall functions for the jsonapi_support module.
 */

/**
 * Implements hook_requirements().
 */
function jsonapi_support_requirements($phase) {
  $requirements = [];
  if ($phase === 'runtime' || $phase === 'install') {
    if (\Drupal::moduleHandler()->moduleExists('jsonapi_extras')) {
      $requirements['jsonapi_support__jsonapi_extras'] = [
        'title' => t('JSONAPI Support compatibility'),
        'value' => t('JSONAPI Support module is not yet compatible with JSONAPI extras module.'),
        'severity' => REQUIREMENT_ERROR,
      ];
    }
  }
  return $requirements;
}