How to report error in production on Symfony2 with a custom ERROR 500 template and an EventListener?

Question

I want to report my error messages on a custom error 500 template. So, I've followed the official symfony tutorial on overriding the default error templates :

app/
└─ Resources/
   └─ TwigBundle/
      └─ views/
         └─ Exception/
            ├─ error404.html.twig
            ├─ error403.html.twig
            ├─ error.html.twig      # All other HTML errors (including 500)
            ├─ error404.json.twig
            ├─ error403.json.twig
            └─ error.json.twig      # All other JSON errors (including 500)

And my error500.html.twig page template looks like that:

            <div class=" details">
              <h3>Oops! Something went wrong.</h3>
              <p> We are fixing it! Please come back in a while.
                  <br/> TEST</p>
                  <div class="alert alert-danger display-hide" {{message ? 'style="display: block;"'}}>
                      <button class="close" data-close="alert"></button>
                      <span>{{message ? message | trans}}</span>
                  </div>
                <p>
                    <a href="{{path('homepage')}}" class="btn red btn-outline"> OK, take me to the homepage </a>
                    <br> </p>
            </div>

Now, I want to write a particular message parameter by using the ExceptionListener that listen onKernelException , as described on the Symfony cookbook :

use Symfony\Component\HttpKernel\Event\GetResponseForExceptionEvent;
use Symfony\Component\HttpFoundation\Response;
use Symfony\Component\HttpKernel\Exception\HttpExceptionInterface;

class ExceptionListener
{
  public function onKernelException(GetResponseForExceptionEvent $event)
  {
    // You get the exception object from the received event
    $exception = $event->getException();
    $message = sprintf(
        'My Error says: %s with code: %s',
        $exception->getMessage(),
        $exception->getCode()
    );

    // Customize your response object to display the exception details
    $response = new Response();
    $response->setContent($message);

    // HttpExceptionInterface is a special type of exception that
    // holds status code and header details
    if ($exception instanceof HttpExceptionInterface) {
        $response->setStatusCode($exception->getStatusCode());
        $response->headers->replace($exception->getHeaders());
    } else {
        $response->setStatusCode(Response::HTTP_INTERNAL_SERVER_ERROR);
    }

    // Send the modified response object to the event
    $event->setResponse($response);
  }
}

I think that I'm only missing the proper way to set the correct template of the Symfony\\Component\\HttpFoundation\\Response . Actually I've been able to intercept the kernel exception event but I return a classic HTML error page without any template.

I'm using PHP 7 and Symfony 2.8.4 .

EDIT

I've found the proper way to intercept the type of exception through the STATUS CODE:

public function onKernelException(GetResponseForExceptionEvent $event)
 {
    $exception = $event->getException();
    $statusCode = $exception->getStatusCode();
    $message = sprintf(
        'ERROR: %s with code: %s',
        $exception->getMessage(),
        $exception->getCode()
    );

    switch ($statusCode) {
      case 404:
          $errorTemplate = 'TwigBundle:Exception:error404.html.twig';
          break;
      case 403:
          $errorTemplate = 'TwigBundle:Exception:error403.html.twig';
          break;
      default:
          $errorTemplate = 'TwigBundle:Exception:error500.html.twig';
          break;
    }
    $response = $this->templating->renderResponse(
        $errorTemplate,
        ['message' => $message]
        );

    // HttpExceptionInterface is a special type of exception that
    // holds status code and header details
    if ($exception instanceof HttpExceptionInterface) {
        $response->setStatusCode($exception->getStatusCode());
        $response->headers->replace($exception->getHeaders());
    } else {
        $response->setStatusCode(Response::HTTP_INTERNAL_SERVER_ERROR);
    }

    $event->setResponse($response);
}

• Handling exception event in Symfony
• public Exception getException()
• Symfony\\Component\\HttpKernel\\Exception
• GetStatusCode()

Answer 1

You need to render the exception template manually.

To do that, pass the templating service to your event listener:

services:
    app.exception_listener:
        class: AppBundle\EventListener\ExceptionListener
        arguments: [ '@templating' ] # Here
        tags:
            - { name: kernel.event_listener, event: kernel.exception }

Then, add the following in your ExceptionListener class:

use Symfony\Bundle\FrameworkBundle\Templating\EngineInterface;
// ...

class ExceptionListener
{
    /** @var EngineInterface */
    private $templating;

    /**
     * @param EngineInterface $templating
     */
    public function __construct(EngineInterface $templating) 
    {
        $this->templating = $templating;
    }

    // ...
}

Then, use it to render your view:

public function onKernelException(GetResponseForExceptionEvent $event)
{
    // ...

    $response = $this->templating->renderResponse(
        'TwigBundle:Exception:error_500.html.twig',
        ['message' => $message]
    );

    $event->setResponse($response);
}

Note
Your custom (overridden) template should be correctly used, otherwise use 'TwigBundle/Exception/error_500.html.twig' as the first argument of $this->templating->renderResponse() rather than 'TwigBundle:Exception:error_500.html.twig' .

To switch the template used depending on the current environment

Copy the original template from the TwigBundle (that you want use in dev) and copy its content in a new app/Resources/TwigBundle/Exception/error_500_dev.html.twig .

Rename your custom template in error_500_prod.html.twig .

Inject the environment as argument to your service:

app.exception_listener:
    # ...
    arguments: [ '@templating', '%kernel.environment%' ]

Set it as ExceptionListener::$env in the constructor like done for the templating.

Then, use it to render the good template:

$response = $this->renderResponse(
    sprintf('TwigBundle:Exception:error_500_%s', $this->env),
    // ...
);