Symfony2: There is no extension able to load the configuration for

Question

I am building an extension to load config files from all installed bundles.

my Extension looks like this:

namespace Acme\MenuBundle\DependencyInjection;
// use ...
use Acme\MenuBundle\DependencyInjection\Configuration;

class AcmeMenuExtension extends Extension {
    public function load(array $configs, ContainerBuilder $container) {

        $configuration = new Configuration();
        $config = $this->processConfiguration($configuration, $configs);

        $finder = new \Symfony\Component\Finder\Finder();
        $finder
            ->directories()
            ->in($container->getParameter('kernel.root_dir') . '/../src/*/*Bundle/Resources')
            ->path('config');

        $possibleLocations = array();
        foreach ($finder as $c_dir) {
            $possibleLocations[] = $c_dir->getPathName();
        }
         
        $loader = new Loader\YamlFileLoader($container, new FileLocator($possibleLocations));
        $loader->load('menu.yml');
    }
}

And then there is my (very simple) Configuration class: I will add a more complex tree in the future, but for now I want it to work with this:

namespace Acme\MenuBundle\DependencyInjection;
// use ...

class Configuration implements ConfigurationInterface {  
    public function getConfigTreeBuilder() {
        $treeBuilder = new TreeBuilder();
        $rootNode = $treeBuilder->root('mw_menu'); 

        $rootNode
            ->children()
                ->scalarNode('mw_menu')->defaultValue('')->end()
            ->end(); 

        return $treeBuilder;
    }
}

For testing I only placed a "menu.yml" file inside the current MenuBundle\Resources\config with this content:

# file: src\Acme\MenuBundle\Resource\config\menu.yml
mw_menu: "some teststring"

For manual testing I use a testAction in a default Controller, which does actually nothing but render an empty template.

Anyway, I get this error:

InvalidArgumentException: There is no extension able to load the configuration for     
"mw_menu" (in {path to symfony}/app/../src/Acme/MenuBundle/Resources\config\menu.yml).
Looked for namespace "mw_menu", found none

How can I fix that?

From what I currently understand, Symfony notices the key 'mw_menu' in the config file, but is not able to find the matching configuration.

I worked along the cookbook article: How to expose a semantic configuration?

Please note: I know of Knp Menu Bundle and similar Bundles but I do want to implement a menu myself.

Additionally I found this notice. Is he right?

Solution

That's because your code:

$rootNode = $treeBuilder->root('mw_menu'); 

$rootNode
    ->children()
    ->scalarNode('mw_menu')->defaultValue('')->end()
    ->end();

means that the config file should look like this:

mw_menu: 
    mw_menu: "some teststring" 

---

An example:

To be more specific, you need to adapt your code to whatever node you want. In general, people use a general root, like mw_menu, and then secondary value like database_driver in the following example:

$rootNode = $treeBuilder->root('mw_menu'); 

$rootNode
    ->children()
    ->scalarNode('database_driver')->defaultValue('orm')->end()
    ->end();

Which would then look like this in config file:

mw_menu: 
    database_driver: mongo_db