UPGRADE FROM 5.0 to 5.1

Config

The signature of method NodeDefinition::setDeprecated() has been updated to NodeDefinition::setDeprecation(string $package, string $version, string $message).
The signature of method BaseNode::setDeprecated() has been updated to BaseNode::setDeprecation(string $package, string $version, string $message).
Passing a null message to BaseNode::setDeprecated() to un-deprecate a node is deprecated
Deprecated BaseNode::getDeprecationMessage(), use BaseNode::getDeprecation() instead

The signature of method Definition::setDeprecated() has been updated to Definition::setDeprecation(string $package, string $version, string $message).
The signature of method Alias::setDeprecated() has been updated to Alias::setDeprecation(string $package, string $version, string $message).
The signature of method DeprecateTrait::deprecate() has been updated to DeprecateTrait::deprecation(string $package, string $version, string $message).
Deprecated the Psr\Container\ContainerInterface and Symfony\Component\DependencyInjection\ContainerInterface aliases of the service_container service, configure them explicitly instead.
Deprecated Definition::getDeprecationMessage(), use Definition::getDeprecation() instead.
Deprecated Alias::getDeprecationMessage(), use Alias::getDeprecation() instead.
The inline() function from the PHP-DSL has been deprecated, use inline_service() instead
The ref() function from the PHP-DSL has been deprecated, use service() instead

Deprecated passing $usePutenv argument to Dotenv's constructor, use Dotenv::usePutenv() instead.

Deprecated LegacyEventDispatcherProxy. Use the event dispatcher without the proxy.

Not configuring the rounding_mode option of the PercentType is deprecated. It will default to \NumberFormatter::ROUND_HALFUP in Symfony 6.
Not passing a rounding mode to the constructor of PercentToLocalizedStringTransformer is deprecated. It will default to \NumberFormatter::ROUND_HALFUP in Symfony 6.
Implementing the FormConfigInterface without implementing the getIsEmptyCallback() method is deprecated. The method will be added to the interface in 6.0.
Implementing the FormConfigBuilderInterface without implementing the setIsEmptyCallback() method is deprecated. The method will be added to the interface in 6.0.
Added argument callable|null $filter to ChoiceListFactoryInterface::createListFromChoices() and createListFromLoader() - not defining them is deprecated.
Using Symfony\Component\Form\Extension\Validator\Util\ServerParams class is deprecated, use its parent Symfony\Component\Form\Util\ServerParams instead.
The NumberToLocalizedStringTransformer::ROUND_* constants have been deprecated, use \NumberFormatter::ROUND_* instead.

Deprecated passing a RouteCollectionBuilder to MicroKernelTrait::configureRoutes(), type-hint RoutingConfigurator instead
Deprecated not setting the "framework.router.utf8" configuration option as it will default to true in Symfony 6.0
Deprecated session.attribute_bag service and session.flash_bag service.

Deprecate Response::create(), JsonResponse::create(), RedirectResponse::create(), and StreamedResponse::create() methods (use __construct() instead)
Made the Mime component an optional dependency

Made WarmableInterface::warmUp() return a list of classes or files to preload on PHP 7.4+ not returning an array is deprecated
Deprecated support for service:action syntax to reference controllers. Use serviceOrFqcn::method instead.

The component has been deprecated, use EnglishInflector from the String component instead.

Deprecated passing Mailgun headers without their "h:" prefix.
Deprecated the SesApiTransport class. It has been replaced by SesApiAsyncAwsTransport Run composer require async-aws/ses to use the new classes.
Deprecated the SesHttpTransport class. It has been replaced by SesHttpAsyncAwsTransport Run composer require async-aws/ses to use the new classes.

Deprecated AmqpExt transport. It has moved to a separate package. Run composer require symfony/amqp-messenger to use the new classes.
Deprecated Doctrine transport. It has moved to a separate package. Run composer require symfony/doctrine-messenger to use the new classes.
Deprecated RedisExt transport. It has moved to a separate package. Run composer require symfony/redis-messenger to use the new classes.
Deprecated use of invalid options in Redis and AMQP connections.
Deprecated not declaring a \Throwable argument in RetryStrategyInterface::isRetryable()
Deprecated not declaring a \Throwable argument in RetryStrategyInterface::getWaitingTime()

[BC BREAK] The ChatMessage::fromNotification() method's $recipient and $transport arguments were removed.
[BC BREAK] The EmailMessage::fromNotification() and SmsMessage::fromNotification() methods' $transport argument was removed.

The signature of method OptionsResolver::setDeprecated() has been updated to OptionsResolver::setDeprecated(string $option, string $package, string $version, $message).
Deprecated OptionsResolverIntrospector::getDeprecationMessage(), use OptionsResolverIntrospector::getDeprecation() instead.

Deprecated the @expectedDeprecation annotation, use the ExpectDeprecationTrait::expectDeprecation() method instead.

Deprecated anonymous: lazy in favor of lazy: true

Before

security:
    firewalls:
        main:
            anonymous: lazy

After

security:
    firewalls:
        main:
            anonymous: true
            lazy: true

Marked the AnonymousFactory, FormLoginFactory, FormLoginLdapFactory, GuardAuthenticationFactory, HttpBasicFactory, HttpBasicLdapFactory, JsonLoginFactory, JsonLoginLdapFactory, RememberMeFactory, RemoteUserFactory and X509Factory as @internal. Instead of extending these classes, create your own implementation based on SecurityFactoryInterface.

Deprecated ROLE_PREVIOUS_ADMIN role in favor of IS_IMPERSONATOR attribute.

before

{% if is_granted('ROLE_PREVIOUS_ADMIN') %}
    <a href="">Exit impersonation</a>
{% endif %}

after

{% if is_granted('IS_IMPERSONATOR') %}
    <a href="">Exit impersonation</a>
{% endif %}

Deprecated LogoutSuccessHandlerInterface and LogoutHandlerInterface, register a listener on the LogoutEvent event instead.
Deprecated DefaultLogoutSuccessHandler in favor of DefaultLogoutListener.
Deprecated RememberMeServicesInterface implementations without a logout(Request $request, Response $response, TokenInterface $token) method.