Nix develop conflicts with home-manager?

Help
1

Hi,

I have a home-manager setup with elixir_1_14 as a package.
I also have a nix flake that looks like this:

{
  description = "Flake with elixir";
  inputs = {
    nixpkgs.url = "nixpkgs/nixos-unstable";    
    flake-utils.url = "github:numtide/flake-utils";
  };

outputs = { self, nixpkgs, flake-utils }:
    flake-utils.lib.eachDefaultSystem
      (system:
        let pkgs = import nixpkgs { 
          inherit system; 
        }; 
        in
        {
          devShells.default = pkgs.mkShell {
            packages = with pkgs; [
              elixir_1_15
            ];
          }; 
        }
      );
  }

When I run nix develop and check the elixir version, I get the correct 1.15.2 version.
But when I run nix develop --command fish, I get the incorrect 1.14.5 version (the package installed by home-manager).

What’s going on here? How can I get the correct package inside the fish shell?

2

I’m not sure if this work but try:

nix develop --command 'fish -C "fish_add_path --path $PATH"'
or
nix develop --command 'fish -C "set -x --unpath PATH $PATH"'

The idea (if it works) is:
nix develop changes your PATH, before executing fish, and fish will use nix develop PATH

1 Like
3

This almost works. The arguments to nix develop are a bit different as seen here: Docs: Add nix develop --command entry by jonringer · Pull Request #7008 · NixOS/nix · GitHub

and only the first command works (with fish_add_path), so the solution is: nix develop --command fish -C "fish_add_path --path $PATH"

Thank you!

1 Like
4

It works with double quotes?
I was expecting $PATH to be resolved when fish runs, that’s why I was using single quotes.

Ie:
nix develop --command fish -C "fish_add_path --path $PATH"
To be:

  1. nix
    • develop
    • –command
    • fish
    • -C
    • “fish_add --path /old/elixir/bin:/usr/bin”
  2. fish
    • -C
    • “fish_add --path /old/elixir/bin:/usr/bin”

And

nix develop --command fish -C 'fish_add_path --path $PATH'
To be:

  1. nix
    • develop
    • –command
    • fish
    • -C
    • ‘fish_add --path $PATH’
  2. fish
    • -C
    • ‘fish_add --path /new/elixir/bin:/usr/bin’
5

you’ve added single quotes around --command 'fish -C ...' and that doesn’t work. The PR I’ve linked shows it with double quotes and that works. I haven’t actual tried to do nix develop -c fish -C 'fish_add_path --path $PATH' but I would expect that to work as well.

6

this suddenly stopped working and I have no idea why.

If I do: nix develop, the nix develop path is the first entry in the path and works correctly
If I do: nix develop -c bash, the first entries are .nix-profile entries:

> nix develop -c bash
[thomas@honor elixir]$ echo $PATH
/home/thomas/.nix-profile/bin:/nix/var/nix/profiles/default/bin:/nix/store/4w22z1kl60hd8z6c50skc58bhbinxqn5-elixir-1.15.2/bin:/nix/store/sprx92b3v49if4m7wi7iahclfsi4nwvn-patchelf-0.15.0/bin:...

and thus this fails.

If I run:

> nix develop -c bash -C 'echo $PATH'
bash: echo $PATH: No such file or directory

which I don’t really understand, with fish I get:

> nix develop -c fish -C 'echo $PATH'
/home/thomas/.local/bin /home/thomas/.nix-profile/bin /nix/var/nix/profiles/default/bin /home/thomas/.bin /nix/store/4w22z1kl60hd8z6c50skc58bhbinxqn5-elixir-1.15.2/bin /nix/store/sprx92b3v49if4m7wi7iahclfsi4nwvn-patchelf-0.

the elixir path is placed after the nix-profile paths, so it doesn’t get precedence.

so I’m now doing this: nix develop -c fish -C 'fish_add_path $nativeBuildInputs/bin' but I’m not sure if this is ok or not. It works though