How to properly enable the twig's sandbox extension in Symfony2? - php

Question

In Symfony2, there is some Twig module disabled by default. One of them is the debug extension, that adds {% debug %} tag (useful on a development environment).
To enable it, nothing really difficult, you add this service to your configuration :
debug.twig.extension:
class: Twig_Extensions_Extension_Debug
tags:
- { name: 'twig.extension' }
But how to enable the {% sandbox %} tag?
My issue is that the extension's constructor takes security policies :
public function __construct(Twig_Sandbox_SecurityPolicyInterface $policy, $sandboxed = false)
{
$this->policy = $policy;
$this->sandboxedGlobally = $sandboxed;
}
By reading the twig documentation, I seen the way to do it natively (without Symfony2) :
$tags = array('if');
$filters = array('upper');
$methods = array(
'Article' => array('getTitle', 'getBody'),
);
$properties = array(
'Article' => array('title', 'body'),
);
$functions = array('range');
$policy = new Twig_Sandbox_SecurityPolicy($tags, $filters, $methods, $properties, $functions);
$sandbox = new Twig_Extension_Sandbox($policy);
$twig->addExtension($sandbox);
I can do something like that inside a service just before using the sandbox, but that's not as clear as the dependancy injection we're used to.
Is there a better / proper way to enable the twig's sandbox extension in Symfony2?

Answer 1

Why not create a private service of the security policy:
parameters:
twig.sandbox.tags:
- if
twig.sandbox.filters:
- upper
twig.sandbox.methods:
Article: [getTitle, getBody]
twig.sandbox.properties:
Article: [title, body]
twig.sandbox.functions:
- range
twig.sandbox.policy:
class: Twig_Sandbox_SecurityPolicy
arguments:
- %twig.sandbox.tags%
- %twig.sandbox.filters%
- %twig.sandbox.methods%
- %twig.sandbox.properties%
- %twig.sandbox.functions%
public: false
You can then inject this service into the twig.sandbox.extension service:
twig.sandbox.extension:
class: Twig_Extension_Sandbox
arguments:
- #twig.sandbox.policy
tags:
- { name: twig.extension }
Done. Marking the twig.sandbox.policy private ensures it won't be accessible using the container (it can still be injected into other services, but I think that's not an issue).
Disclaimer: I haven't tested this and it probably needs some tweaking before it actually works so don't copy paste!