Adding intelligent configuration merging to FrameworkExtension

FrameworkExtension.php

<?php

class FrameworkExtension extends Extension
{
    public function configLoad(array $configs, ContainerBuilder $container)
    {
        $loader = new XmlFileLoader($container, __DIR__.'/../Resources/config');

        $loader->load('web.xml');
        $loader->load('form.xml');
        $loader->load('services.xml');

        if ($container->getParameter('kernel.debug')) {
            $loader->load('debug.xml');
            $container->setDefinition('event_dispatcher', $container->findDefinition('debug.event_dispatcher'));
            $container->setAlias('debug.event_dispatcher', 'event_dispatcher');
        }

        $this->doConfigLoad($this->configMerge($configs), $container);

        $this->addClassesToCompile(array(
            'Symfony\\Component\\HttpFoundation\\ParameterBag',
            'Symfony\\Component\\HttpFoundation\\HeaderBag',
            'Symfony\\Component\\HttpFoundation\\Request',
            'Symfony\\Component\\HttpFoundation\\Response',
            'Symfony\\Component\\HttpFoundation\\ResponseHeaderBag',

            'Symfony\\Component\\HttpKernel\\HttpKernel',
            'Symfony\\Component\\HttpKernel\\ResponseListener',
            'Symfony\\Component\\HttpKernel\\Controller\\ControllerResolver',
            'Symfony\\Component\\HttpKernel\\Controller\\ControllerResolverInterface',

            'Symfony\\Bundle\\FrameworkBundle\\RequestListener',
            'Symfony\\Bundle\\FrameworkBundle\\Controller\\ControllerNameParser',
            'Symfony\\Bundle\\FrameworkBundle\\Controller\\ControllerResolver',
            'Symfony\\Bundle\\FrameworkBundle\\Controller\\Controller',

            'Symfony\\Component\\EventDispatcher\\EventInterface',
            'Symfony\\Component\\EventDispatcher\\Event',
            'Symfony\\Component\\EventDispatcher\\EventDispatcherInterface',
            'Symfony\\Component\\EventDispatcher\\EventDispatcher',
            'Symfony\\Bundle\\FrameworkBundle\\EventDispatcher',

            'Symfony\\Component\\Form\\FormContext',
            'Symfony\\Component\\Form\\FormContextInterface',
        ));
    }

    /**
     * Merges a set of configurations into one, normalized array.
     *
     * @param array $configs An array of option arrays to merge
     * @return array
     */
    protected function configMerge(array $configs)
    {
        // The default and available options. These are very specific to this method.
        $options = array(
            'cache_warmer' => null,
            'charset'      => null,
            'csrf_protection' => array(
                'enabled'    => null,
                'field_name' => null,
                'secret'     => null,
            ),
            'document_root' => null,
            'error_handler' => null,
            'esi' => array(
                'enabled' => null,
            ),
            'i18n' => null,
            'ide' => null,
            'param_converter' => null,
            'profiler' => array(
                'only_exceptions' => null,
                'matcher' => array(
                    'ip'      => null,
                    'path'    => null,
                    'service' => null,
                ),
            ),
            'router' => array(
                'cache_warmer' => null,
                'resource'     => null,
            ),
            'session' => array(
                'auto_start'      => null,
                'class'           => null,
                'default_locale'  => null,
                'storage_id'      => 'native',
                // Storage driver options
                'name'            => null,
                'lifetime'        => null,
                'path'            => null,
                'domain'          => null,
                'secure'          => null,
                'httponly'        => null,
                'pdo.db_table'    => null,
                'pdo.db_id_col'   => null,
                'pdo.db_data_col' => null,
                'pdo.db_time_col' => null,
            ),
            'templating' => array(
                'assets_version'   => null,
                'assets_base_urls' => null,
                'cache'            => null,
                'cache_warmer'     => null,
                'engines'          => array(),
                'loaders'          => array(),
            ),
            'test' => null,
            'translator' => array(
                'enabled'  => null,
                'fallback' => null,
            ),
            'validation' => array(
                'enabled'     => null,
                'annotations' => array(
                    'enabled'    => null,
                    'namespaces' => array(),
                ),
            ),
        );

        foreach ($configs as $config) {
            $config = $this->normalizeKeys($config);

            if (isset($config['templating']) && is_array($config['templating'])) {
                $config['templating']['engines'] = $this->normalizeConfig($config['templating'], 'engine');
                $config['templating']['loaders'] = $this->normalizeConfig($config['templating'], 'loader');
                unset($config['templating']['engine'], $config['templating']['loader']);
            }

            if (isset($config['validation']['annotations']) && is_array($config['validation']['annotations'])) {
                $config['validation']['annotations']['namespaces'] = $this->normalizeConfig($config['validation']['annotations'], 'namespace');
                unset($config['validation']['annotations']['namespace']);
            }

            $options = $this->mergeOptions($options, $config);
        }

        return $options;
    }

    /**
     * Merges a single option level.
     *
     * @param array  $options The array that will be modified and returned
     * @param array  $config  The array to be merged in
     * @param string $path    The base path for this option level
     * @throw InvalidArgumentException When an unsupported option is found
     */
    protected function mergeOptions(array $options, array $config, $path = null)
    {
        if ($unsupportedOptions = array_diff_key($config, $options)) {
            throw new \InvalidArgumentException('The following options are not supported: '.implode(', ', $unsupportedOptions));
        }

        foreach ($options as $key => $value) {
            if (array_key_exists($key, $config)) {
                $optionPath = $path ? $path . '.' . $key : $key;

                if (is_array($value) && !is_array($config[$key])) {
                    throw new \InvalidArgumentException(sprintf('Expected array type for option "%s", %s given', $optionPath, gettype($config[$key])));
                }

                switch ($optionPath) {
                    case 'templating.engines':
                    case 'templating.loaders':
                        $options[$key] = array_unique(array_merge($value, $config[$key]));
                        break;

                    case 'validation.annotations.namespaces':
                        $options[$key] = array_merge($value, $config[$key]);
                        break;

                    default:
                        if (is_array($value)) {
                            $options[$key] = $this->mergeOptions($value, $config[$key], $optionPath);
                        } else {
                            $options[$key] = $config[$key];
                        }
                }
            }
        }

        return $options;
    }
}