That’s good to hear @avh4. In my opinion we need to be careful around changes in binwrap. It might be problematic on NixOS right now but it provides support for Mac, Windows and plenty of Linux distros. In my opinion it’s better to be slightly more defensive - we should avoid breaking what is working fine.
Furthermore I don’t think the issue is with binwrap itself but with the way it’s used in npm scripts. I was thinking I about patching it in a way so that binwrap would work as usual but than I though nixpkgs way is usually to build from source and cache the binary so this approach (not using binwrap) is more nixpkgs way in the end I think.
Not sure if you know but elm-format is already in nixpkgs so anyone on NixOS or with nix can just install it via nix-env -i elmPackages.elm-format.