Lorri misbehaves when the shell has disallowedReferences

[michaelpj]

Describe the bug
lorri fails in some cases if the shell derivation uses disallowedReferences or disallowedRequisites. This can be useful as a safety guard to avoid e.g. situations where your shell depends on building too much stuff (happened to me at work!).

To Reproduce
Steps to reproduce the behavior:

{ pkgs ? (import <nixpkgs> {}) }:
pkgs.mkShell {
  buildInputs = [ pkgs.hello ];
  disallowedReferences = [ pkgs.hello ];
  # so you can nix-build this file and check that it's okay
  nobuildPhase = ''touch $out'';
}

Observe:

• nix-build shell.nix is fine
• lorri will fail with logs: [LogLine("these derivations will be built:"), LogLine(" /nix/store/w23dsh466vh9clalnd0mc8hsgxli5gj8-lorri-keep-env-hack-nix-shell.drv"), LogLine("building \'/nix/store/w23dsh466vh9clalnd0mc8hsgxli5gj8-lorri-keep-env-hack-nix-shell.drv\'..."), LogLine("output \'/nix/store/mggmmwyrpkywaavix36l0il7mcfcvsxg-lorri-keep-env-hack-nix-shell\' is not allowed to refer to the following paths:"), LogLine(" /nix/store/8a6lbpbxbc5lc60ljwhw69sszr25ys5f-hello-2.10"), LogLine("error: build of \'/nix/store/w23dsh466vh9clalnd0mc8hsgxli5gj8-lorri-keep-env-hack-nix-shell.drv\' failed")]

Expected behavior
lorri does not fail if the normal use of the shell.nix does not fail.

Additional context
I'm pretty sure the problem is here:

lorri/src/logged-evaluation.nix

Line 39 in 008646a

drv.drvAttrs // {

This keeps all the drv attributes but messes with the inputs, thus making disallowedReferences and disallowedRequisites do the wrong thing. A simple fix would probably be to just strip those attributes.