Cachix not working?

[Thieso]

Hello,

I am trying to install a ros environment and as far as I understand I should not need to build all the packages when using the binary cache. However, when I use the flake.nix:

{
  description = "ROS Test";

  nixConfig = {
    substituters = [ 
      "https://nix-community.cachix.org"
      "https://cache.nixos.org/"
      "https://ros.cachix.org"
     ];
    trusted-public-keys = [
      "cache.nixos.org-1:6NCHdD59X431o0gWypbMrAURkbJ16ZPMQFGspcDShjY="
      "nix-community.cachix.org-1:mB9FSh9qf2dCimDSUo8Zy7bkq5CX+/rkCWyvRCYg3Fs="
      "ros.cachix.org-1:dSyZxI8geDCJrwgvCOHDoAfOm5sV1wCPjBkKL+38Rvo="
    ];
  };

  inputs = {
    flake-utils.url = "github:numtide/flake-utils";
    ros-flake.url = "github:lopsided98/nix-ros-overlay";
  };

  outputs = { self, nixpkgs, flake-utils, ros-flake }: 
      let
        system = "x86_64-linux";
        pkgs = import nixpkgs {
          inherit system;
          overlays = [ros-flake.overlays.default];
        };
      in
      {
        devShells.x86_64-linux.default = pkgs.mkShell {
          name = "ros devenv";
          buildInputs = with pkgs; with pkgs.rosPackages.humble; [
            ros-core
            colcon
            geometry-msgs
            sensor-msgs
            rviz2
          ];
        };
      };
}

and then start the shell with

nix develop

it starts building >100 packages which is not what I would expect. Am I doing something wrong?

Thanks for the help

[wentasah]

It's likely because you try build the ROS packages against a "random" version of nixpkgs and not the version, that was used for populating the cache. Try adding

nixpkgs.follows = "ros-flake/nixpkgs";

to the inputs of your flake.

BTW, this was the reason why I submitted #359 yesterday :-) However, if I do the change, I still have to compile some packages. I'm not sure why. Maybe, it has something to do with #353.

[Thieso]

Ah perfect thank you. Yes #359 is fully supported by me. I struggled a bit and created my example from the flake.nix files in the issues. Thanks for the help.

[Thieso]

So after all, this does not fix the issue. It creates a different amount of packages to build, such that I assume the new package versions are used but it still builds >100 packages. Can someone confirm that the Cachix is working for them for a simple example?

[lopsided98]

There's definitely something wrong with the GitHub actions build, so probably many packages aren't being built.

[Thieso]

Ah I see. I will try to take a look but sadly I am still a beginner in Nix.

[Thieso]

Ok that works now again, Thank you