interface ServiceSubscriberInterface

interface ServiceSubscriberInterface {
    
    /**
     * Returns an array of service types (or {@see SubscribedService} objects) required
     * by such instances, optionally keyed by the service names used internally.
     *
     * For mandatory dependencies:
     *
     *  * ['logger' => 'Psr\Log\LoggerInterface'] means the objects use the "logger" name
     *    internally to fetch a service which must implement Psr\Log\LoggerInterface.
     *  * ['loggers' => 'Psr\Log\LoggerInterface[]'] means the objects use the "loggers" name
     *    internally to fetch an iterable of Psr\Log\LoggerInterface instances.
     *  * ['Psr\Log\LoggerInterface'] is a shortcut for
     *  * ['Psr\Log\LoggerInterface' => 'Psr\Log\LoggerInterface']
     *
     * otherwise:
     *
     *  * ['logger' => '?Psr\Log\LoggerInterface'] denotes an optional dependency
     *  * ['loggers' => '?Psr\Log\LoggerInterface[]'] denotes an optional iterable dependency
     *  * ['?Psr\Log\LoggerInterface'] is a shortcut for
     *  * ['Psr\Log\LoggerInterface' => '?Psr\Log\LoggerInterface']
     *
     * additionally, an array of {@see SubscribedService}'s can be returned:
     *
     *  * [new SubscribedService('logger', Psr\Log\LoggerInterface::class)]
     *  * [new SubscribedService(type: Psr\Log\LoggerInterface::class, nullable: true)]
     *  * [new SubscribedService('http_client', HttpClientInterface::class, attributes: new Target('githubApi'))]
     *
     * @return string[]|SubscribedService[] The required service types, optionally keyed by service names
     */
    public static function getSubscribedServices() : array;

}