Rector rules that implement Rector\Core\Contract\Rector\ConfigurableRectorInterface can be configured.
Typical example is Rector\Renaming\Rector\Name\RenameClassRector:
<?php
// rector.php
declare(strict_types=1);
use Rector\Renaming\Rector\Name\RenameClassRector;
use Symfony\Component\DependencyInjection\Loader\Configurator\ContainerConfigurator;
return static function (ContainerConfigurator $containerConfigurator): void {
$services = $containerConfigurator->services();
$services->set(RenameClassRector::class)
->call('configure', [[
// we use constant for keys to save you from typos
RenameClassRector::OLD_TO_NEW_CLASSES => [
'App\SomeOldClass' => 'App\SomeNewClass',
],
]]);
};