How can I access config parameters defined in a custom extension? - symfony

Question

I created a custom extension in my app for the sole purpose of being able to define config in yaml. I am unable to retrieve configuration params with ParameterBagInterface. What am I missing with the following approach?
config/packages/myapp.yaml
myapp:
foo:
bar: '%env(MYAPP_BAR)%'
I created a command to test if I could retrieve the config. When run, I get the error:
The parameter "myapp" must be defined.
class FooCommand extends Command
{
...
public function __construct(ParameterBagInterface $params, $name = '')
{
$this->params = $params;
parent::__construct();
}
...
protected function execute(InputInterface $input, OutputInterface $output): int
{
dd($this->params->get('myapp'));
...
I set all this up by creating the following files and modifying Kernel.php
src/DependencyInjection/Configuration.php
src/DependencyInjection/MyappExtension.php
Note that in the extension file below, the dd($config) prints everything defined in myapp.yaml.
src/DependencyInjection/MyappExtension.php
class MyappExtension extends Extension
{
public function load(array $configs, ContainerBuilder $container)
{
$configuration = new Configuration();
$config = $this->processConfiguration($configuration, $configs);
// This dumps my config as an array
// dd($config);
}
}
src/DependencyInjection/Configuration.php
class Configuration implements ConfigurationInterface
{
public function getConfigTreeBuilder()
{
$treeBuilder = new TreeBuilder('myapp');
$treeBuilder->getRootNode()
->children()
->arrayNode('foo')
->children()
->scalarNode('bar')->end()
->end()
->end()
->end();
return $treeBuilder;
}
src/Kernel.php (1 line modification)
...
protected function configureContainer(ContainerBuilder $container, LoaderInterface $loader): void
{
$container->addResource(new FileResource($this->getProjectDir().'/config/bundles.php'));
$container->registerExtension(new MyappExtension());
...