DependencySerializationTrait.php

<?php

namespace Drupal\Core\DependencyInjection;

use Drupal\Core\Entity\EntityStorageInterface;
use Symfony\Component\DependencyInjection\ContainerInterface;

/**
 * Provides dependency injection friendly methods for serialization.
 */
trait DependencySerializationTrait {
    
    /**
     * An array of service IDs keyed by property name used for serialization.
     *
     * @var array
     */
    protected $_serviceIds = [];
    
    /**
     * An array of entity type IDs keyed by the property name of their storages.
     *
     * @var array
     */
    protected $_entityStorages = [];
    
    /**
     * {@inheritdoc}
     */
    public function __sleep() {
        $this->_serviceIds = [];
        $vars = get_object_vars($this);
        foreach ($vars as $key => $value) {
            if (is_object($value) && isset($value->_serviceId)) {
                // If a class member was instantiated by the dependency injection
                // container, only store its ID so it can be used to get a fresh object
                // on unserialization.
                $this->_serviceIds[$key] = $value->_serviceId;
                unset($vars[$key]);
            }
            elseif ($value instanceof ContainerInterface) {
                $this->_serviceIds[$key] = 'service_container';
                unset($vars[$key]);
            }
            elseif ($value instanceof EntityStorageInterface) {
                // If a class member is an entity storage, only store the entity type ID
                // the storage is for so it can be used to get a fresh object on
                // unserialization. By doing this we prevent possible memory leaks when
                // the storage is serialized when it contains a static cache of entity
                // objects and additionally we ensure that we'll not have multiple
                // storage objects for the same entity type and therefore prevent
                // returning different references for the same entity.
                $this->_entityStorages[$key] = $value->getEntityTypeId();
                unset($vars[$key]);
            }
        }
        return array_keys($vars);
    }
    
    /**
     * {@inheritdoc}
     */
    public function __wakeup() {
        // Tests in isolation potentially unserialize in the parent process.
        $phpunit_bootstrap = isset($GLOBALS['__PHPUNIT_BOOTSTRAP']);
        if ($phpunit_bootstrap && !\Drupal::hasContainer()) {
            return;
        }
        $container = \Drupal::getContainer();
        foreach ($this->_serviceIds as $key => $service_id) {
            // In rare cases, when test data is serialized in the parent process,
            // there is a service container but it doesn't contain all expected
            // services. To avoid fatal errors during the wrap-up of failing tests, we
            // check for this case, too.
            if ($phpunit_bootstrap && !$container->has($service_id)) {
                continue;
            }
            $this->{$key} = $container->get($service_id);
        }
        $this->_serviceIds = [];
        // In rare cases, when test data is serialized in the parent process, there
        // is a service container but it doesn't contain all expected services. To
        // avoid fatal errors during the wrap-up of failing tests, we check for this
        // case, too.
        if ($this->_entityStorages && (!$phpunit_bootstrap || $container->has('entity_type.manager'))) {
            
            /** @var \Drupal\Core\Entity\EntityTypeManagerInterface $entity_type_manager */
            $entity_type_manager = $container->get('entity_type.manager');
            foreach ($this->_entityStorages as $key => $entity_type_id) {
                $this->{$key} = $entity_type_manager->getStorage($entity_type_id);
            }
        }
        $this->_entityStorages = [];
    }

}