escape string in extension

[connorhu]

There is an extension which, under certain conditions, either renders a template or returns only a string. When it returns a string, I want to escape it, but when the render is done, the render handles the escaping. Because of this, this extension runs with 'is_safe' => ['html'].
This would be a "cheap" solution for escaping the string:

$escaper = $twig->getExtension(EscaperExtension::class);
return $escaper->escape($twig, self::stringValueForPresentationField($presentation, $field), 'html');

Since the escape method is internal, I feel this is less trusted, but I couldn't find a better solution. What would be a nice, fast and safe solution in this case?
I also considered doing a render, but I think that solution is resource expensive.

[fabpot]

You use this instead (see https://github.com/twigphp/Twig/blob/3.x/doc/deprecated.rst):

$escaper = $twig->getRuntime(EscaperRuntime::class);
return $escaper->escape($twig, self::stringValueForPresentationField($presentation, $field), 'html');

[connorhu]

Thank you very much for your answer!