Enum class not found when trying to use it in settings.php

Question

I defined an enum in a custom module:

namespace Drupal\my_module\Enum;

enum BuildType: string {
  case Apple = 'apple_build';
  case Orange = 'orange_build';
}

And I want to use it in settings.php to change the config directory of the site:

settings.php:

$build_type = BuildType::from(getenv('build_type'));

$settings['config_sync_directory'] = dirname(DRUPAL_ROOT) . '/config/base_' . $build_type->value;

$settings['custom_translations_directory'] = dirname(DRUPAL_ROOT) . '/translations/' . $build_type->value;

However, when I do this, I get a namespace error:

Error: Class "Drupal\my_module\Enum\BuildType" not found in /var/www/html/web/sites/default/settings.custom.php on line 14 #0 /var/www/html/web/sites/default/settings.php(32): include()

How can I correctly namespace my enum for use in settings.php?

Answer 1

The settings.php file is loaded from DrupalKernel::initializeSettings(), which is called from DrupalKernel::handle() before DrupalKernel::boot().

See the code in Settings::initialize(), called by DrupalKernel::initializeSettings().

if (is_readable($app_root . '/' . $site_path . '/settings.php')) {
  require $app_root . '/' . $site_path . '/settings.php';
}

This means that when the code in settings.php is executed, the dependency injection container hasn't yet initialized, the services aren't yet available, and modules are not loaded. Classes/interfaces/traits defined from contributed/custom modules are not yet available either.

Since the settings.php file does not have access to classes/interfaces a module defines, it should load the file containing the class/interface definition directly or define the class/interface itself. Since the settings.php file is loaded with require, the code to load the class file or declaring the class should be wrapped in an if statement.

if (!class_exists('BuildType')) {
  // Load the class file or declare the class.
}

Answer 2

Here's the final code based on apaderno's answer:

settings.php:

if (!class_exists('BuildType') {
  enum BuildType: string {
    case Apple = 'apple_build';
    case Orange = 'orange_build';
  }
}

$build_type = BuildType::from(getenv('build_type'));

$settings['config_sync_directory'] = dirname(DRUPAL_ROOT) . '/config/base_' . $build_type->value;

$settings['custom_translations_directory'] = dirname(DRUPAL_ROOT) . '/translations/' . $build_type->value;