Issues installing Nickel in a Nix flake devshell

[carletes]

Issues installing Nickel in a Nix flake devshell

[vkleen]

Thanks for trying it out! There seem to be some incompatibilities with rust-overlay and the newest nixpkgs, I guess. There's two ways of fixing this, either you keep the nixpkgs version from Nickel pinned:

    nickel = {
      url = "github:tweag/nickel/1.0-release";
      # inputs.nixpkgs.follows = "nixpkgs"; <--- just remove this
      inputs.flake-utils.follows = "flake-utils";
    };

or you can fetch a new version of the rust-overlay like so:

  inputs = {
    nixpkgs.url = "nixpkgs/nixos-unstable";
    flake-utils.url = "github:numtide/flake-utils";
    rust-overlay = {
      url = "github:oxalica/rust-overlay";
      inputs.nixpkgs.follows = "nixpkgs";
      inputs.flake-utils.follows = "flake-utils";
    };

    nickel = {
      url = "github:tweag/nickel/1.0-release";
      inputs.nixpkgs.follows = "nixpkgs";
      inputs.flake-utils.follows = "flake-utils";
      inputs.rust-overlay.follows = "rust-overlay";
    };
  };

  outputs = { self, nixpkgs, flake-utils, nickel, ... }: # <--- you also need the ... or explicitly rust-overlay as an extra input

[vkleen]

For reference, the issue is oxalica/rust-overlay#121, which has been fixed in rust-overlay at oxalica/rust-overlay@c949d34.

[carletes]

Thanks for your prompt reply, @vkleen! Your second option (adding an explicit rust-overlay input) does the trick.

I also realised that Nickel 1.0 is already in https://github.com/NixOS/nixpkgs, so the following works for me as well:

{
  description = "Nickel experiments";

  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 {
          buildInputs = with pkgs; [
            nickel

            # Keep this line if you use bash.
            pkgs.bashInteractive
          ];
        };
      });
}