There is! It’s called Nickel, and nickel-nix is an experimental implementation that integrates it into Nix.
And while that is a welcome development, I can’t help but feel there is just too few people doing too many things. A lot of work in the Nix ecosystem is still conceptual, there is divided attention between the old and new CLI, way more tickets are being opened than completed, same for PRs.
And let’s not forget, almost all contributors to Nix offer consulting on how to integrate Nix as far as I understand, so the amount of stuff that has to be done is just completely overwhelming compared to the amount of stuff that can be done.
I mean just look at one of the core team’s weekly meeting notes, the issue tracker and the PR List;
8 Issues/PRs discussed. 21 Issues opened. 11 PRs opened. All within one week. Maybe I’m pessimistic, but it seems to me that there is a severe lack of manpower. Most issues aren’t even triaged, ever.