contacts.install

<?php

 /**
  * @file
  * Install related hook implementations for the contacts module.
  */

use Drupal\Core\Installer\Exception\InstallerException;

/**
 * Implements hook_requirements().
 */
function contacts_requirements($phase) {
  $requirements = [];

  // Test admin theme is enabled.
  if ($phase == 'install') {
    /* @var $themeHandler \Drupal\Core\Extension\ThemeHandler */
    $themeHandler = \Drupal::service('theme_handler');

    if (!$themeHandler->themeExists('contacts_theme')) {
      // See if the theme is available to install. If it is we'll do that in
      // contacts_module_preinstall().
      $theme_data = \Drupal::service('theme_handler')->rebuildThemeData();

      // If the theme is not available, show an error.
      if (!isset($theme_data['contacts_theme'])) {
        $requirements['contacts_theme_missing'] = [
          'description' => t('Contacts theme missing: to enable the contacts module you must first enable the contacts theme.'),
          'severity' => REQUIREMENT_ERROR,
        ];
      }
      // Otherwise check for any missing dependencies.
      else {
        $themes = ['contacts_theme' => NULL];

        while (in_array(NULL, $themes, TRUE)) {
          foreach (array_keys($themes, NULL, TRUE) as $theme) {
            foreach ($theme_data[$theme]->requires as $requirement) {
              // See if we are missing this dependency.
              if (!isset($theme_data[$requirement['name']])) {
                $themes[$theme] = FALSE;
              }
              // Otherwise, add the dependency to the list to be checked.
              else {
                $themes += [$requirement['name'] => NULL];
              }
            }

            // If we've got this far, we have this themes' dependencies.
            $themes[$theme] = TRUE;
          }
        }

        // If we have missing dependencies, report an error.
        if ($missing = array_keys($themes, FALSE, TRUE)) {
          $requirements['contacts_theme_dependency'] = [
            'description' => t('Contacts theme missing dependencies @dependencies: to enable the contacts module you must first enable the contacts theme.', [
              '@dependencies' => implode(', ', $missing),
            ]),
            'severity' => REQUIREMENT_ERROR,
          ];
        }
      }

    }
  }

  return $requirements;
}

/**
 * Implements hook_module_preinstall().
 *
 * Module config depends on a layout provided by the theme.
 */
function contacts_module_preinstall($module) {
  if ($module == 'contacts') {
    /* @var $themeHandler \Drupal\Core\Extension\ThemeHandler */
    $themeHandler = \Drupal::service('theme_handler');

    if (!$themeHandler->themeExists('contacts_theme')) {
      // Try to install theme.
      $result = \Drupal::service('theme_installer')
        ->install(['contacts_theme']);
      if (!$result) {
        throw new InstallerException('Failed to install contacts theme.');
      }
    }
  }
}