AddEventAliasesPass has been added, allowing applications and bundles to extend the event alias mapping used by RegisterListenersPass.event attribute of the kernel.event_listener tag optional for FQCN events.EventDispatcherInterface::dispatch() method should be updated to dispatch($event, string $eventName = null), not doing so is deprecatedEvent class, use Symfony\Contracts\EventDispatcher\Event insteadkernel.event_listener by defaultTraceableEventDispatcher::getOrphanedEvents() method has been added.TraceableEventDispatcherInterface has been deprecated.ContainerAwareEventDispatcher classreset() method to the TraceableEventDispatcherInterfaceTraceableEventDispatcherInterface without the reset() method has been deprecated.getListenerPriority($eventName, $listener) has been added to the
EventDispatcherInterface.Event::setDispatcher(), Event::getDispatcher(), Event::setName()
and Event::getName() have been removed.
The event dispatcher and the event name are passed to the listener call.