ContextProvidersPass.php

<?php

namespace Drupal\Core\DependencyInjection\Compiler;

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

/**
 * Adds the context provider service IDs to the context manager.
 */
class ContextProvidersPass implements CompilerPassInterface {
    
    /**
     * {@inheritdoc}
     *
     * Passes the service IDs of all context providers to the context repository.
     */
    public function process(ContainerBuilder $container) {
        $context_providers = [];
        foreach (array_keys($container->findTaggedServiceIds('context_provider')) as $id) {
            $context_providers[] = $id;
        }
        $definition = $container->getDefinition('context.repository');
        $definition->addArgument($context_providers);
    }

}