Summary of Changes

To register commands to the console application, the best practice is to have a console plugin catching the Joomla\Application\ApplicationEvents::BEFORE_EXECUTE event and adding the command via $event->getApplication()->addCommand(). However, this comes with a performance penalty of having instantiated a Joomla\Console\Command\AbstractCommand class object. This issue is in part caused by the design of Joomla\Console\Loader\LoaderInterface which in essence specifies a read-only API once the loader is instantiated, which is suitable for the environments that Symfony applications are built for (and where the joomla/console package design came from, in addition to internally using it to the extent practical) or less dynamic Joomla! Framework applications. This read-only API isn't a great fit for the CMS environment.

To bypass this performance penalty, a new Joomla\CMS\Console\Loader\WritableLoaderInterface is introduced with a Joomla\CMS\Console\Loader\WritableContainerLoader implementation of it, and the console application adjusted to use this writable loader. This means plugins would now be able to add the command to the lazy loader and have it instantiated as late as possible as a container service instead of requiring the command class always be instantiated (and yes, even though this is a CLI thing, you still don't want a performance trade-off of potentially instantiating 50 unused classes).

Testing Instructions

Running php cli/joomla.php with this patch applied still works. Unit tests for the new class pass. If creating a console plugin to add a command, this snippet is the gist of what you'd do to register a command.

use Joomla\Application\Event\ApplicationEvent;
use Joomla\CMS\Console\Loader\WritableLoaderInterface;
use Joomla\CMS\Factory;
use Joomla\DI\Container;

public function onBeforeExecute(ApplicationEvent $event): void
{
    $serviceId = 'my.command';

    Factory::getContainer()->share(
        $serviceId,
        function (Container $container) {
            // do stuff to create command class and return it
        },
        true
    );

    Factory::getContainer()->get(WritableLoaderInterface::class)->add('my:command', $serviceId);
}