J4.x

J4.x:Writing A CLI Application

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Joomla 4 comes with an updated way of writing CLI Commands. We'll try and cover the most important changes here and teach you how to write your own CLI commands in Joomla 4.

Brief Overview of changes in Joomla 4

When you built a CLI application in Joomla 4 you'd create a full Application instance by extending JApplicationCli. In Joomla 4 instead of building up a full new application instance we've built a new Joomla Application that uses the Symfony Console component to make the process of integrating your components much easier than it was previously. The Joomla 3 way of building an application through JApplication will work in Joomla 4, however is deprecated and will be removed in Joomla 5.

The new Console Package (a new package in version 2 of the Joomla Framework) contains the base code and it's extended in the CMS to add support for things like using JInput.

The advantage of the new way is that we have a single application that means using JApplication::isClient('cli') will work. The introduction of \\Joomla\\CMS\\Application\\CMSApplicationInterface means that all applications within Joomla should have a consistent set of methods available for extensions to use.

Creating a Command

The most rudimentary command just prints a title and some text into the terminal.

	/**
	 * The default command name
	 *
	 * @var    string
	 * @since  4.0.0
	 */
	protected static $defaultName = 'commandgroup:commandname';

	/**
	 * Internal function to execute the command.
	 *
	 * @param   InputInterface   $input   The input to inject into the command.
	 * @param   OutputInterface  $output  The output to inject into the command.
	 *
	 * @return  integer  The command exit code
	 *
	 * @since   4.0.0
	 */
	protected function doExecute(InputInterface $input, OutputInterface $output): int
	{
		$symfonyStyle = new SymfonyStyle($input, $output);

		$symfonyStyle->title('Hello World Command Title');

		// You might want to do some stuff here in Joomla

		$symfonyStyle->success('Hello World!');

		return 0;
	}

	/**
	 * Configure the command.
	 *
	 * @return  void
	 *
	 * @since   4.0.0
	 */
	protected function configure(): void
	{
		$this->setDescription('This command prints hello world to whoever calls it');
		$this->setHelp(
			<<<EOF
The <info>%command.name%</info> command prints hello world to whoever calls it
<info>php %command.full_name%</info>
EOF
		);
	}

Let's cover the 3 parts of this code:

  • configure function: Configures information about the command setting up information in the class which is shown when a user lists help information for the command* doExecute function: This method does the work of the command - you'd normally go and execute a Joomla Component here (i.e. Dispatch a components dispatcher)* defaultName property: This is the command name that is run when executed (remember this we'll come back to it in a second!)If you need more help there's an excellent Video produced as part of our GSOC 2018 program to help you out!

Adding the command to the Application by Plugin

Inside your plugin you're going to register to the event \Joomla\Application\ApplicationEvents::BEFORE_EXECUTE using the method getSubscribedEvents. The following Example required a command RunHelloCommand and registers it.

class PlgsystemMyConsole extends CMSPlugin implements SubscriberInterface
{

    public static function getSubscribedEvents(): array
    {
        return [
            \Joomla\Application\ApplicationEvents::BEFORE_EXECUTE => 'registerCommands',
        ];
    }

    public function registerCommands(): void
    {
        $serviceId = 'hello.world';

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

        Factory::getContainer()->get(\Joomla\CMS\Console\Loader\WritableLoaderInterface::class)->add('hello:world', $serviceId);
    }

}

This method registerCommands adds your command into the Dependency Injection Container then registers that command against the name of the command for when it's called by the Joomla CLI Application (note the first parameter of WritableLoaderInterface::add() should be the same as the defaultName property inside your Command Class.

Calling the Command

To call the command you just created you need to run it through the Joomla CLI Command:

php cli/joomla.php my:command