NIX_BIN_PREFIX: unbound variable

[aaschmid]

Since version 1.2.3 I get the following error

~/work/some-dir
direnv: loading ~/work/some-dir/.envrc
direnv: using nix
/nix/store/4aifrh1mksd52aam92a4zc6hzjvargrk-nix-direnv-1.2.3/share/nix-direnv/direnvrc:145: NIX_BIN_PREFIX: unbound variable

It works with version 1.2.1.

My system info is

 - system: `"x86_64-darwin"`
 - host os: `Darwin 19.6.0, macOS 10.15.7`
 - multi-user?: `yes`
 - sandbox: `yes`
 - version: `nix-env (Nix) 2.3.10`
 - channels(user): `"darwin, home-manager"`
 - channels(root): `"nixpkgs-21.05pre272202.7fd33568097, darwin, home-manager"`
 - nixpkgs: `/nix/var/nix/profiles/per-user/root/channels/nixpkgs`

Which other information are required?

I haven't investigated further yet, but if you have a tip for me how to fix, I can also try to provide a PR

[Mic92]

This is set here:

nix-direnv/direnvrc

Line 4 in 04f80bf

NIX_BIN_PREFIX=$(command -v nix-shell)

Do you have by chance anything in your .envrc that unsets NIX_BIN_PREFIX?

[aaschmid]

I am not sure about your question. I use use_nix() and there NIX_BIN_PREFEX is set:

nix-direnv/direnvrc

Line 145 in 04f80bf

path=$("${NIX_BIN_PREFIX}nix-instantiate" --find-file nixpkgs)

.

Most of my .envrc files only have use nix. I tried with various shell.nix files using nodejs, java, python with virtual envs.

Does that help?

[Mic92]

I am not sure about your question. I use use_nix() and there NIX_BIN_PREFEX is set:

nix-direnv/direnvrc

Line 145 in 04f80bf

path=$("${NIX_BIN_PREFIX}nix-instantiate" --find-file nixpkgs)

.

Most of my .envrc files only have use nix. I tried with various shell.nix files using nodejs, java, python with virtual envs.

Does that help?

Can you put set -x in your ~/.direnvrc before nix-direnv is sourced and
give me the output of an example .envrc.
I currently cannot reproduce what is going on in your case.

[aaschmid]

Here is the result of my first and in depth investigation:

1. My direnvrc installed via home-manager has following line to check for $NIX_BIN_PREFIX: if [[ -z ${NIX_BIN_PREFIX:-/nix/store/q0z2kvkgrpvaipa87jl98qh7g5pym5fj-nix-2.3.10/bin/} ]]; then
2. Changing this to if [[ -z ${NIX_BIN_PREFIX:-} ]]; then and it works as expected
3. This change comes from pkgs/tools/misc/nix-direnv/default.nix line 18: --replace "\''${NIX_BIN_PREFIX:-}" "\''${NIX_BIN_PREFIX:-${nix}/bin/}" \
4. Creating an overlay with following fixes it:

   nixpkgs.overlays = [
    (self: super: {
      nix-direnv = super.nix-direnv.overrideAttrs (oldAttrs: rec {
        # Substitute instead of wrapping because the resulting file is getting sourced, not executed:
        postPatch = ''
          substituteInPlace direnvrc \
            --replace "grep" "${super.gnugrep}/bin/grep"
        '';
      });
    })
  ];

Sorry for not doing deep investigation earlier. If you aggree with that change I can create a PR for it on nixpkgs repo.

[aaschmid]

The other alternative might be changing

--replace "\''${NIX_BIN_PREFIX:-}" "\''${NIX_BIN_PREFIX:-${nix}/bin/}" \

to

--replace "\''${NIX_BIN_PREFIX}" "\''${NIX_BIN_PREFIX:-${nix}/bin/}" \

(Note the missing :- in order to set a proper default for $NIX_BIN_PREFIX if there is a problem with setting it at the beginning ...

[Mic92]

The other alternative might be changing

--replace "\''${NIX_BIN_PREFIX:-}" "\''${NIX_BIN_PREFIX:-${nix}/bin/}" \

to

--replace "\''${NIX_BIN_PREFIX}" "\''${NIX_BIN_PREFIX:-${nix}/bin/}" \

(Note the missing :- in order to set a proper default for $NIX_BIN_PREFIX if there is a problem with setting it at the beginning ...

yes please.

[aaschmid]

@Mic92: Should I also change the nixFlakes usage in the

nix-direnv/default.nix

Line 10 in aca3a32

sed -i "2iNIX_BIN_PREFIX=${nixFlakes}/bin/" direnvrc

as we did in nixpkgs?

[Mic92]

@Mic92: Should I also change the nixFlakes usage in the

nix-direnv/default.nix

Line 10 in aca3a32

sed -i "2iNIX_BIN_PREFIX=${nixFlakes}/bin/" direnvrc

as we did in nixpkgs?

See https://github.com/NixOS/nixpkgs/pull/114622/files#r584597612