[7.x] Allow setting the event handler queue via a getQueue() method

[lupinitylabs]

Using queued event listeners, it is possible to set the queue the resulting job should be executed on using the $queue attribute. This attribute is then adopted by the dispatcher.

However, it is not possible to set the queue name from the config, the environment or otherwise programatically, because the listener instance is created without invoking the constructor in Dispatcher::createListenerAndJob(). Thus, trying to set the queue name in the constructor or anywhere else in the Listener has no effect.

This pull request proposes a non-breaking change to the Dispatcher class that allows a user to set the queue name by defining a getQueue() method within the Listener, as it is already done with retryAfter and retryUntil methods.

If no getQueue method is defined, the code falls back to use the $queue attribute or null, as it was before.

The benefit of this change is to provide developers with a flexible way to influence the target queues instead of having to hard code them.

[taylorotwell]

public function __construct()
{
    $this->queue = 'whatever-you-want';
}

[lupinitylabs]

public function __construct()
{
    $this->queue = 'whatever-you-want';
}

Sure, as I described above, that was my first attempt, but it doesn't work because the listener is instantiated using $listener = (new ReflectionClass($class))->newInstanceWithoutConstructor(); hence the pull request.

Please check out a quick project I hacked together at https://github.com/lupinitylabs/queuename in the hopes of making myself clearer.

Please note: the same issue exists with setting the tries property, so the pull request should probably even be extended by a method to set tries, too.

[lupinitylabs]

@taylorotwell Any chance to have this re-opened?