References to pkgs from ~/.config/nixpkgs/config.nix produce infinite recursion

[lilyball]

Describe the bug

When using ~/.config/nixpkgs/config.nix to configure nixpkgs, this file may optionally be a function that takes a single { pkgs }: parameter. This is necessary when adding configuration for blocklistedLicenses in order to reference the licenses in question. Example usage:

{ pkgs }:

{
  blocklistedLicenses = with pkgs.lib.licenses; [ agpl3Only agpl3Plus ];
}

As of #240433 (darwin.stdenv: Darwin stdenv rework), the reference to pkgs within this file produces an infinite recursion error:

error:
       … <borked>

         at «none»:0: (source not available)

       … while evaluating a branch condition

         at /Users/lily/Dev/Nix/nixpkgs/pkgs/stdenv/booter.nix:99:7:

           98|     thisStage =
           99|       if args.__raw or false
             |       ^
          100|       then args'

       (stack trace truncated; use '--show-trace' to show the full trace)

       error: infinite recursion encountered

       at /Users/lily/.config/nixpkgs/config.nix:4:30:

            3| {
            4|   blocklistedLicenses = with pkgs.lib.licenses; [ agpl3Only agpl3Plus ];
             |                              ^
            5| }

Steps To Reproduce

Steps to reproduce the behavior:

1. Ensure your nixpkgs contains commit a845397
2. Ensure the file ~/.config/nixpkgs/config.nix contains the contents listed above and that there is no NIXPKGS_CONFIG env var (or set NIXPKGS_CONFIG to the path of a file containing the above)
3. Run something like nix-instantiate --eval --expr 'with import ./. {}; hello.version' (if from a nixpkgs checkout, or import <nixpkgs> if appropriate).

Expected behavior

This should run successfully (in this case, printing the version of the hello package).

Additional context

Merely doing something like blocklistedLicenses = assert builtins.isAttrs pkgs; []; is sufficient to cause this issue. Sticking this in some of the other config values (like allowUnfree) doesn't cause a problem, though I didn't test all of them. Looking at the full stack trace I think it's because it's trying to test the validity of ../../build-support/cc-wrapper during bootstrap, so it's likely just the allowlisted/blocklisted licenses that will end up evaluated here.

I really wish the config here was given { lib } instead, but that's a backwards-incompatible change.

Notify maintainers

Folks involved in the relevant PR: @reckenrode @viraptor @veprbl @emilazy @Atemu @tjni @willcohen @siraben @uri-canva

Metadata

Please run nix-shell -p nix-info --run "nix-info -m" and paste the result.

[user@system:~]$ nix run nixpkgs#nix-info -- -m
 - system: `"x86_64-darwin"`
 - host os: `Darwin 22.6.0, macOS 10.16`
 - multi-user?: `no`
 - sandbox: `yes`
 - version: `nix-env (Nix) 2.15.1`
 - channels(lily): `"darwin, home-manager"`
 - channels(root): `""`
 - nixpkgs: `/etc/nix/inputs/nixpkgs`

[reckenrode]

This also appears broken on Linux.

$ nix run nixpkgs#nix-info -- -m
 - system: `"x86_64-linux"`
 - host os: `Linux 6.1.41, NixOS, 22.11 (Raccoon), 22.11.20230703.ea4c80b`
 - multi-user?: `yes`
 - sandbox: `yes`
 - version: `nix-env (Nix) 2.11.1`
 - nixpkgs: `/etc/nix/inputs/nixpkgs`
$  git rev-list a845397 -n 1
a845397040d1b85cec4ee41edb8598d8086c3d95
$ NIXPKGS_CONFIG=$(pwd)/../bug/config.nix nix-instantiate --eval --expr 'with import ./. {}; hello.version' --show-trace
error: infinite recursion encountered

       at /home/reckenrode/nixpkgs/../bug/config.nix:4:30:

            3| {
            4|   blocklistedLicenses = with pkgs.lib.licenses; [ agpl3Only agpl3Plus ];
             |                              ^
            5| }

       … while evaluating anonymous lambda

       at /home/reckenrode/nixpkgs/pkgs/stdenv/generic/check-meta.nix:41:40:

           40|   hasBlocklistedLicense = assert areLicenseListsValid; attrs:
           41|     hasLicense attrs && lib.lists.any (l: builtins.elem l blocklist) (lib.lists.toList attrs.meta.license);
             |                                        ^
           42|

       … from call site
# etc

[reckenrode]

The nixos-22.11 channel works, so I’m using that as a known good commit to do a git bisect on Linux.

[reckenrode]

git bisect points to d7aad24, which is the logic the Darwin stdenv rework copied. 😫

[lilyball]

I'm curious if anyone actually has any use for referencing anything other than lib from pkgs in the config file. In theory we could just hand the config file { pkgs = { inherit lib; }; } and call it a day. Though I'm guessing there's at least one person out there who's actually accessing other things from pkgs for whatever reason (I suppose there's a potential use of e.g. permittedInsecurePackages = [ pkgs.someInsecurePackage.name ]).