The view-dependent stuff is in fact separated from the business conversion logic and can be used in a non-web context if you want.

Here's the version for use in a view context: https://github.com/rails/rails/blob/master/actionview/lib/ac...

You can see that this method has some XSS prevention logic.

Here's the converter itself: https://github.com/rails/rails/blob/master/activesupport/lib...