WIP: enable __structuredAttrs in stdenv.mkDerivation

[FRidh]

This is an attempt at adding support for __structuredAttrs.

Things done

• Tested using sandboxing (nix.useSandbox on NixOS, or option sandbox in nix.conf on non-NixOS)
• Built on platform(s)
  • NixOS
  • macOS
  • other Linux distributions
• Tested via one or more NixOS test(s) if existing and applicable for the change (look inside nixos/tests)
• Tested compilation of all pkgs that depend on this change using nix-shell -p nix-review --run "nix-review wip"
• Tested execution of all binary files (usually in ./result/bin/)
• Determined the impact on package closure size (by running nix path-info -S before and after)
• Ensured that relevant documentation is up to date
• Fits CONTRIBUTING.md.

Notify maintainers

cc @

[FRidh]

While .attrs.sh is bash-compatible, the declared attributes are different than what existed. E.g., the output $out is now ${outputs["out"]}. I suppose for compatibility we should ensure the original variables still function.

[globin]

Feel free to steal from: https://github.com/mayflower/nixpkgs/tree/structured-attrs

[FRidh]

oh, nice! It certainly seems there is still a lot of work required. Is Mayflower going with this any further?

[globin]

I don't have time to progress further for now. Building stdenv partly suceeds to build in my branch, in the sense that as far as I can see the only problem is that I have a problem with input ordering or similar so that the bootstrap tools are referenced instead of stuff built during stdenv bootstrapping. but didn't manage to debug that further until now.

I know @matthewbauer, @Ericson2314 and @edolstra at least were interested in this too.

[globin]

Furthermore I'd propose pushing my branch to NixOS/nixpkgs and create a follow-up PR so that a larger number of people can work on this concurrently? Feel free to just go ahead and do so if you think that should be the way to move forward on this.