Have you ever submitted a PR to try get something like this into Rails 4?

[nickcoyne]

I'm wondering why this behaviour has not been implemented into Rails 4?

[kares]

Hey Nick, no I have not really ... I feel like it's an ugly hack and to do it properly I would need to refactor quite a lot of internals. But if you feel like it - feel free to modify and submit my pieces if you find the useful.

[nickcoyne]

This goes way beyond my knowledge of rails/rack internals. I've created an issue for Rails - rails/rails#16982