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    <h3>Editing: NotTaggedControllerValueResolver.php</h3>
    <textarea name="content" rows="20" cols="80">&lt;?php

/*
 * This file is part of the Symfony package.
 *
 * (c) Fabien Potencier &lt;fabien@symfony.com&gt;
 *
 * For the full copyright and license information, please view the LICENSE
 * file that was distributed with this source code.
 */

namespace Symfony\Component\HttpKernel\Controller\ArgumentResolver;

use Psr\Container\ContainerInterface;
use Symfony\Component\DependencyInjection\Exception\RuntimeException;
use Symfony\Component\HttpFoundation\Request;
use Symfony\Component\HttpKernel\Controller\ArgumentValueResolverInterface;
use Symfony\Component\HttpKernel\ControllerMetadata\ArgumentMetadata;

/**
 * Provides an intuitive error message when controller fails because it is not registered as a service.
 *
 * @author Simeon Kolev &lt;simeon.kolev9@gmail.com&gt;
 */
final class NotTaggedControllerValueResolver implements ArgumentValueResolverInterface
{
    private $container;

    public function __construct(ContainerInterface $container)
    {
        $this-&gt;container = $container;
    }

    /**
     * {@inheritdoc}
     */
    public function supports(Request $request, ArgumentMetadata $argument): bool
    {
        $controller = $request-&gt;attributes-&gt;get('_controller');

        if (\is_array($controller) &amp;&amp; \is_callable($controller, true) &amp;&amp; \is_string($controller[0])) {
            $controller = $controller[0].'::'.$controller[1];
        } elseif (!\is_string($controller) || '' === $controller) {
            return false;
        }

        if ('\\' === $controller[0]) {
            $controller = ltrim($controller, '\\');
        }

        if (!$this-&gt;container-&gt;has($controller) &amp;&amp; false !== $i = strrpos($controller, ':')) {
            $controller = substr($controller, 0, $i).strtolower(substr($controller, $i));
        }

        return false === $this-&gt;container-&gt;has($controller);
    }

    /**
     * {@inheritdoc}
     */
    public function resolve(Request $request, ArgumentMetadata $argument): iterable
    {
        if (\is_array($controller = $request-&gt;attributes-&gt;get('_controller'))) {
            $controller = $controller[0].'::'.$controller[1];
        }

        if ('\\' === $controller[0]) {
            $controller = ltrim($controller, '\\');
        }

        if (!$this-&gt;container-&gt;has($controller)) {
            $controller = (false !== $i = strrpos($controller, ':'))
                ? substr($controller, 0, $i).strtolower(substr($controller, $i))
                : $controller.'::__invoke';
        }

        $what = sprintf('argument $%s of &quot;%s()&quot;', $argument-&gt;getName(), $controller);
        $message = sprintf('Could not resolve %s, maybe you forgot to register the controller as a service or missed tagging it with the &quot;controller.service_arguments&quot;?', $what);

        throw new RuntimeException($message);
    }
}
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