UPGRADE FROM 4.0 to 4.1

Config

Implementing ParentNodeDefinitionInterface without the getChildNodeDefinitions() method is deprecated.

Console

Deprecated the setCrossingChar() method in favor of the setDefaultCrossingChar() method in TableStyle.
The Processor class has been made final
Deprecated the setHorizontalBorderChar() method in favor of the setDefaultCrossingChars() method in TableStyle.
Deprecated the getHorizontalBorderChar() method in favor of the getBorderChars() method in TableStyle.
Deprecated the setVerticalBorderChar() method in favor of the setVerticalBorderChars() method in TableStyle.
Deprecated the getVerticalBorderChar() method in favor of the getBorderChars() method in TableStyle.
Added support for iterable messages in write and writeln methods of Symfony\Component\Console\Output\OutputInterface. If you have a custom implementation of the interface, you should make sure it works with iterable as well.

DependencyInjection

Deprecated the TypedReference::canBeAutoregistered() and TypedReference::getRequiringClass() methods.
Deprecated support for auto-discovered extension configuration class which does not implement ConfigurationInterface.

EventDispatcher

The TraceableEventDispatcherInterface has been deprecated.

Form

Deprecated the ChoiceLoaderInterface implementation in CountryType, LanguageType, LocaleType and CurrencyType, use the choice_loader option instead.

Before:

class MyCountryType extends CountryType
{
    public function loadChoiceList()
    {
        // override the method
    }
}

After:

class MyCountryType extends AbstractType
{
    public function getParent()
    {
        return CountryType::class;
    }

    public function configureOptions(OptionsResolver $resolver)
    {
        $resolver->setDefault('choice_loader', ...); // override the option instead
    }
}

Added help option to the form field. If you have custom Form extension for it, you should remove it. Also remove it from the custom form theme.

FrameworkBundle

Deprecated bundle:controller:action and service:action syntaxes to reference controllers. Use serviceOrFqcn::method instead where serviceOrFqcn is either the service ID when using controllers as services or the FQCN of the controller.

Before:

bundle_controller:
    path: /
    defaults:
        _controller: FrameworkBundle:Redirect:redirect

service_controller:
    path: /
    defaults:
        _controller: app.my_controller:myAction

After:

bundle_controller:
    path: /
    defaults:
        _controller: Symfony\Bundle\FrameworkBundle\Controller\RedirectController::redirectAction

service_controller:
    path: /
    defaults:
        _controller: app.my_controller::myAction

Deprecated Symfony\Bundle\FrameworkBundle\Controller\ControllerNameParser
Warming up a router in RouterCacheWarmer that does not implement the WarmableInterface is deprecated and will not be supported anymore in 5.0.
The RequestDataCollector class has been deprecated. Use the Symfony\Component\HttpKernel\DataCollector\RequestDataCollector class instead.

HttpFoundation

Passing the file size to the constructor of the UploadedFile class is deprecated.
The getClientSize() method of the UploadedFile class is deprecated. Use getSize() instead.
Deprecated Symfony\Component\HttpFoundation\Request::getSession() when no session has been set. Use Symfony\Component\HttpFoundation\Request::hasSession() instead.

Security

The ContextListener::setLogoutOnUserChange() method is deprecated.
Using the AdvancedUserInterface is now deprecated. To use the existing functionality, create a custom user-checker based on the Symfony\Component\Security\Core\User\UserChecker.
AuthenticationUtils::getLastUsername() now always returns a string.
The ExpressionVoter::addExpressionLanguageProvider() method is deprecated. Register the provider directly on the injected ExpressionLanguage instance instead.

SecurityBundle

The logout_on_user_change firewall option is deprecated.
The switch_user.stateless firewall option is deprecated, use the stateless option instead.
The SecurityUserValueResolver class is deprecated, use Symfony\Component\Security\Http\Controller\UserValueResolver instead.

Serializer

Decoding XML with XmlEncoder now ignores comment node types by default.

Translation

The FileDumper::setBackup() method is deprecated.
The TranslationWriter::disableBackup() method is deprecated.

TwigBundle

Deprecated relying on the default value (false) of the twig.strict_variables configuration option. You should use %kernel.debug% explicitly instead, which will be the new default in 5.0.

Validator

The Email::__construct() 'strict' property is deprecated. Use 'mode'=>"strict" instead.
Calling EmailValidator::__construct() method with a boolean parameter is deprecated, use EmailValidator("strict") instead.
Deprecated the checkDNS and dnsMessage options of the Url constraint.

Workflow

Deprecated the DefinitionBuilder::reset() method, use the clear() one instead.
Deprecated the add method in favor of the addWorkflow method in Workflow\Registry.
Deprecated SupportStrategyInterface in favor of WorkflowSupportStrategyInterface.
Deprecated the class ClassInstanceSupportStrategy in favor of the class InstanceOfSupportStrategy.
Deprecated passing the workflow name as 4th parameter of Event constructor in favor of the workflow itself.