symfony2 dynamic config blogpost config.yml

config.yml

tactician:
  default_bus: queued
  commandbus:
    default:
      middleware:
        - tactician.middleware.command_handler
    queued:
      middleware:
        - tactician.middleware.queued_command_handler

Configuration.php

// ..Bundle/DependencyInjectionConfiguration::getConfigTreeBuilder
$rootNode
    ->validate()
        ->ifTrue(function($config) {
            return is_array($config) &&
            array_key_exists('default_bus', $config) &&
            array_key_exists('commandbus', $config);
        })
        ->then(function($config) {
            $busNames = array_keys($config[‘commandbus’]);
            if (!in_array($config['default_bus'], $busNames)) {
                // Throw an exception
            }
        })
    ->end()
;