New in Symfony 6.1: Service Autowiring Attributes

Contributed by Kevin Bond in #45657 and #45783

Attributes are probably one of the new features in PHP that have the most positive impact on the way we develop applications. They add structured, machine-readable metadata information in code. In Symfony we added support for them in:

• New in Symfony 5.2: Routing PHP attributes
• New in Symfony 5.2: Constraints as PHP attributes
• New in Symfony 5.2: Controller argument attributes
• New in Symfony 5.3: Service Autoconfiguration attributes
• New in Symfony 5.3: Autowiring Iterators/Locators and Aliases with Attributes
• New in Symfony 6.1: Service Decoration Attributes

In Symfony 6.1 we're introducing another feature related to attributes so you can instruct the autowiring logic with PHP attributes.

By default, the autowiring logic reads the type-hints on your constructor (/setters) and that's enough to automate the resolution of most dependencies.

However, sometimes you may need another service than the default one, or you may need a scalar value, etc. In similar situations, you had to use explicit configuration in your config/services.yaml file.

Thanks to the new #[Autowire] attribute, you can now instruct the autowiring logic to replace the default rule by a more specific one in case you need so:

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use Symfony\Component\DependencyInjection\Attribute\Autowire;

class MyService
{
    public function __construct(
        #[Autowire(service: 'some_service')]
        private $service1,

        #[Autowire(expression: 'service("App\\Mail\\MailerConfiguration").getMailerMethod()')]
        private $service2,

        #[Autowire('%env(json:file:resolve:AUTH_FILE)%')]
        private $parameter1,

        #[Autowire('%kernel.project_dir%/config/dir')]
        private $parameter2,
    ) {}

    // ...
}