git log

• nixos: introduce nixpkgs.pkgsFun, deprecate nixpkgs.pkgs

  Despite what the description of nixpkgs.pkgs option said, the
  use of nixpkgs.pkgs actually produced 2x evaluation slowdown
  after a54a799 because NixOS had
  to reevaluate nixpkgs to reapply overlays the second time.

  The use of nixpkgs.pkgs also complicates many things, e.g. why
  are overlays reapplied, but configuration is not? It also
  prevents proper config type checking via Typed nixpkgs.config with Gentoo-like use-flags #56227.

  nixpkgs.pkgsFun approach is much simpler and doesn't have
  any of those problems, half of the code in that module can also be
  dropped after nixpkgs.pkgs option is completely removed.

  If such an option is really needed for optimizion purposes of
  nixosTests or whatever (which I doubt, note that e.g.
  NixOps users actually lose on average by using it for above
  reasons), it should be made internal and hidden from users.

nix-instantiate environment

• Host OS: Linux 4.9, SLNOS 19.09
• Nix: nix-env (Nix) 2.2
• Multi-user: yes
• Sandbox: yes
• NIXPKGS_CONFIG:

{
  checkMeta = true;
  doCheckByDefault = true;
}

nix-env -qaP diffs

• On x86_64-linux:
  • Updated (2):
    • tests.nixos-functions.nixos-test
    • tests.nixos-functions.nixosTest-test
• On aarch64-linux: ditto
• On x86_64-darwin: noop

/cc @roberth @Ericson2314 @matthewbauer from git-blame, @7c6f434c