[Nix-dev] Are nix-shells supposed to nest?

[Peter Simons]

Hi folks,

the Github issue #13011 [1] asks an interesting question, namely: can we
nest nix-shell environments? A simple experiment suggests it's possible,
but the result you get when do you it is quite surprising:

  $ nix-shell -p haskell.compiler.ghc784 --run 'nix-shell -p haskell.compiler.ghc7103 --run "ghc --version"'
  The Glorious Glasgow Haskell Compilation System, version 7.8.4

Apparently, the inner shell ends up being the outer shell in that
example. So now I wonder: can someone explain why $PATH is set up in
that example as it is?

And what is our policy with regard to that feature? Can users of
nix-shell expect nested shells to work in some predictable way? Or is
that something you're not supposed to do?

Best regards,
Peter


[1] https://github.com/NixOS/nixpkgs/issues/13011