shellify allows generating shell.nix from ad-hoc #Nix environments:

https://github.com/danielrolls/shellify

Why isn't this a core feature??

@cbleslie Congratulations!

@buherator Guix actually has this, guix shell --export-manifest. Disappointing indeed that Nix doesn't. I like the package availability that switching to Nix gave me access to, but they should definitely steal some ideas for CLI design from Guix.