RegisterSerializationClassesCompilerPass.php

<?php

namespace Drupal\serialization;

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

/**
 * Adds services tagged 'normalizer' and 'encoder' to the Serializer.
 */
class RegisterSerializationClassesCompilerPass implements CompilerPassInterface {
    
    /**
     * Adds services to the Serializer.
     *
     * @param \Symfony\Component\DependencyInjection\ContainerBuilder $container
     *   The container to process.
     */
    public function process(ContainerBuilder $container) {
        $definition = $container->getDefinition('serializer');
        // Retrieve registered Normalizers and Encoders from the container.
        foreach ($container->findTaggedServiceIds('normalizer') as $id => $attributes) {
            // The 'serializer' service is the public API: mark normalizers private.
            $container->getDefinition($id)
                ->setPublic(FALSE);
            $priority = $attributes[0]['priority'] ?? 0;
            $normalizers[$priority][] = new Reference($id);
        }
        foreach ($container->findTaggedServiceIds('encoder') as $id => $attributes) {
            // The 'serializer' service is the public API: mark encoders private.
            $container->getDefinition($id)
                ->setPublic(FALSE);
            $priority = $attributes[0]['priority'] ?? 0;
            $encoders[$priority][] = new Reference($id);
        }
        // Add the registered Normalizers and Encoders to the Serializer.
        if (!empty($normalizers)) {
            $definition->replaceArgument(0, $this->sort($normalizers));
        }
        if (!empty($encoders)) {
            $definition->replaceArgument(1, $this->sort($encoders));
        }
        // Find all serialization formats known.
        $formats = [];
        $format_providers = [];
        foreach ($container->findTaggedServiceIds('encoder') as $service_id => $attributes) {
            $format = $attributes[0]['format'];
            $formats[] = $format;
            if ($provider_tag = $container->getDefinition($service_id)
                ->getTag('_provider')) {
                $format_providers[$format] = $provider_tag[0]['provider'];
            }
        }
        $container->setParameter('serializer.formats', $formats);
        $container->setParameter('serializer.format_providers', $format_providers);
    }
    
    /**
     * Sorts by priority.
     *
     * Order services from highest priority number to lowest (reverse sorting).
     *
     * @param array $services
     *   A nested array keyed on priority number. For each priority number, the
     *   value is an array of Symfony\Component\DependencyInjection\Reference
     *   objects, each a reference to a normalizer or encoder service.
     *
     * @return array
     *   A flattened array of Reference objects from $services, ordered from high
     *   to low priority.
     */
    protected function sort($services) {
        krsort($services);
        return array_merge([], ...$services);
    }

}