Symfony 8.1 is a minor release. According to the Symfony release process, there should be no significant backward compatibility breaks. Minor backward compatibility breaks are prefixed in this document with [BC BREAK], make sure your code is compatible with these entries before upgrading. Read more about this in the Symfony documentation.

If you're upgrading from a version below 8.0, follow the 8.0 upgrade guide first.

• [BC BREAK] Add object support to input options and arguments' default by changing the $default type to mixed in InputArgument, InputOption, #[Argument] and #[Option]
• Add optional $format argument to SymfonyStyle::createProgressBar(), SymfonyStyle::progressStart(), and SymfonyStyle::progressIterate() to allow passing a custom ProgressBar format string
• Deprecate passing both InputArgument::REQUIRED and InputArgument::OPTIONAL modes to InputArgument constructor
• Deprecate passing more than one out of InputOption::VALUE_NONE, InputOption::VALUE_REQUIRED and InputOption::VALUE_OPTIONAL modes to InputOption constructor

• Deprecate configuring options alias, parent, synthetic, file, arguments, properties, configurator or calls when using from_callable
• Deprecate default index/priority methods when defining tagged locators/iterators; use the #[AsTaggedItem] attribute instead
• Deprecate named autowiring aliases that don't use #[Target]

   use Symfony\Component\DependencyInjection\Attribute\Target;
  
   public function __construct(
  +    #[Target]
       private StorageInterface $imageStorage,
   ) {

• Deprecate setting an $aliasMap in RegisterMappingsPass. Namespace aliases are no longer supported in Doctrine.

• Always set LIBXML_NONET in Crawler::addXmlContent() so external entities cannot trigger network requests

• Add argument $deprecationsNamespacesMapping to DebugClassLoader::enable() to configure namespace-to-vendor remapping for deprecation checks

• Deprecate passing boolean as the second argument of ValidatorExtension and FormTypeValidatorExtension's constructors; pass a ViolationMapperInterface instead
• Add argument $violationMapper to ValidatorExtensionTrait and TypeTestCase's getExtensions() methods

• Deprecate calling Filesystem::mirror() with option copy_on_windows, use option follow_symlinks instead

• Deprecate setting the framework.profiler.collect_serializer_data config option

• Deprecate the framework.http_cache.terminate_on_cache_hit config option

• Deprecate parameters router.request_context.scheme and router.request_context.host; use the router.request_context.base_url parameter or the framework.router.default_uri config option instead

• Deprecate setting framework.http_client.default_options.caching.max_ttl to null, use a positive integer instead

• Deprecate senders nesting level for messenger routing config; use string or a list of strings instead

• Deprecate registering console commands by overriding Bundle::registerCommands(), use the #[AsCommand] attribute or the console.command service tag instead

• Deprecate calling FrameworkExtension::load() directly without first loading ServicesBundle's extension. Tests that wire up a ContainerBuilder by hand should now do:

  +new ServicesBundle()->getContainerExtension()->load([], $container);
  
   new FrameworkExtension()->load($config, $container);

  For real kernels, FrameworkBundle carries a #[RequiredBundle(ServicesBundle::class)] attribute that should be processed already.

• Deprecate passing null as $maxTtl to CachingHttpClient, pass a positive integer instead

• Deprecate setting public properties of Request and Response objects directly; use setters or constructor arguments instead
• ParameterBag::getInt() and ParameterBag::getBoolean() now throw UnexpectedValueException instead of silently returning 0/false when the value cannot be converted

• Deprecate BundleInterface, use the one from the DependencyInjection component instead

• Deprecate MergeExtensionConfigurationPass, use the one from the DependencyInjection component instead

• Deprecate FileLocator, use the one from the DependencyInjection component instead

• Deprecate ServicesResetter, ServicesResetterInterface, and ResettableServicePass, use the ones from the DependencyInjection component instead

• Deprecate passing a non-flat list of attributes to Controller::setController()

• Deprecate the Symfony\Component\HttpKernel\DependencyInjection\Extension class, use the parent Symfony\Component\DependencyInjection\Extension\Extension class instead:

  - use Symfony\Component\HttpKernel\DependencyInjection\Extension;
  + use Symfony\Component\DependencyInjection\Extension\Extension;
  
  class ExampleExtension extends Extension
  {
      // ...
  }

• Deprecate passing a ControllerArgumentsEvent to the ViewEvent constructor; pass a ControllerArgumentsMetadata instead

• Deprecate Bundle::registerCommands(), use the #[AsCommand] attribute or the console.command service tag instead of overriding this method

• Serializers now return Envelope<MessageDecodingFailedException> on decode failure instead of throwing; custom serializers that still throw are supported via a BC fallback in receivers
• Receivers no longer delete messages from the queue on decode failure; they are routed through the normal retry/failure transport path instead
• Add argument $fetchSize to ReceiverInterface::get() and QueueReceiverInterface::getFromQueues()
• Deprecate StopWorkerOnTimeLimitListener in favor of using the time_limit worker option
• Add forceRetry() method to RecoverableExceptionInterface

• Add getParentRoleNames() method to RoleHierarchyInterface
• Make RoleHierarchyInterface::getReachableRoleNames() return roles as both keys and values
• Deprecate SameOriginCsrfTokenManager::onKernelResponse(), SameOriginCsrfTokenManager::clearCookies() and SameOriginCsrfTokenManager::persistStrategy(); this logic is now handled automatically by SameOriginCsrfListener
• Deprecate passing the $eraseCredentials argument to AuthenticatorManager::__construct(), as the eraseCredentials() method was removed in Symfony 8.0

• Deprecate the security.erase_credentials config option and the security.authentication.manager.erase_credentials container parameter, as the eraseCredentials() method was removed in Symfony 8.0

• Deprecate datetime constructor as a fallback, in version 9.0 a Symfony\Component\Serializer\Exception\NotNormalizableValueException will be thrown when a date could not be parsed using the default format
• Change the signature of PartialDenormalizationException::__construct($data, array $errors) to __construct(mixed $data, array $notNormalizableErrors, array $extraAttributesErrors = [])
• Deprecate PartialDenormalizationException::getErrors(), use getNotNormalizableValueErrors() instead

• Add argument $format to Ulid::isValid()

• Deprecate ConstraintValidatorInterface::initialize() and ConstraintValidatorInterface::validate() in favor of ConstraintValidatorInterface::validateInContext(). The ConstraintValidator abstract class handles the context management when extending it. When writing tests with ConstraintValidatorTestCase, use the new validate method to abstract the way to use the constraint validator.

  Your code	Action required
  extends ConstraintValidator	Nothing to do
  implements ConstraintValidatorInterface directly	Implement validateInContext()
  tests using ConstraintValidatorTestCase	Call $this->validate() instead of $this->validator->validate()

• Implementing ConstraintViolationListInterface without implementing findByCodes() is deprecated

• Deprecate Hydrator and Instantiator classes, use deepclone_hydrate() from the deepclone extension instead