Generic class to allow overwriting a service

ServiceAliasPass.php

<?php

namespace Symfony\Component\DependencyInjection\Compiler;

use Symfony\Component\DependencyInjection\Compiler\CompilerPassInterface;
use Symfony\Component\DependencyInjection\ContainerBuilder;
use Symfony\Component\DependencyInjection\Alias;

/**
 * Overwrites a service with an alias to a new service, and injects the old service as a parent of the new one
 *
 * @author Christophe Coevoet <stof@notk.org>
 */
class ServiceAliasPass implements CompilerPassInterface
{
    private $oldService;
    private $newService;
    private $renameTo;

    public function __construct($oldService, $newService, $renameTo = null)
    {
        $this->oldService = $oldService;
        $this->newService = $newService;
        $this->renameTo = $renameTo;

        if (!$this->renameTo) {
            $this->renameTo = $this->newService . '.parent';
        }
    }

    public function process(ContainerBuilder $container)
    {
        if ($container->hasAlias($this->oldService)) {
            // Service we're overwriting is an alias.
            // Register a private alias for this service to inject it as the parent
            $container->setAlias($this->renameTo, new Alias((string) $container->getAlias($this->oldService), false));
        } else {
            // Service we're overwriting is a definition.
            // Register it again as a private service to inject it as the parent
            $definition = $container->getDefinition($this->oldService);
            $definition->setPublic(false);
            $container->setDefinition($this->renameTo, $definition);
        }

        $container->setAlias($this->oldService, $this->newService);
    }
}