Infinite recursion when using namespace in home configuration

[Bear-03]

Hello.

I am trying to build a simple flake with snowfall, but when I try to use a namespaced module in my home configuration, I get the following error:

building the system configuration...
error:
       … while calling the 'head' builtin
         at /nix/store/4r8s42c9mwfvgdlxv0izb1cmlzrsb5nz-source/lib/attrsets.nix:1574:11:
         1573|         || pred here (elemAt values 1) (head values) then
         1574|           head values
             |           ^
         1575|         else

       … while evaluating the attribute 'value'
         at /nix/store/4r8s42c9mwfvgdlxv0izb1cmlzrsb5nz-source/lib/modules.nix:816:9:
          815|     in warnDeprecation opt //
          816|       { value = addErrorContext "while evaluating the option `${showOption loc}':" value;
             |         ^
          817|         inherit (res.defsFinal') highestPrio;

       … while evaluating the option `system.build.toplevel':

       … while evaluating definitions from `/nix/store/4r8s42c9mwfvgdlxv0izb1cmlzrsb5nz-source/nixos/modules/system/activation/top-level.nix':

       … while evaluating the option `assertions':

       … while evaluating definitions from `/nix/store/q1ss75nhmjiydyqw8lbzwbx7cqk8z0qq-source/nixos/common.nix':

       … while evaluating the module argument `namespace' in "/nix/store/9bwi858z3pzcgf9g40bwqvr52lz2zycd-s6wc8mk3jb8ja70aawm5s0ndmda1cyvh-source/homes/x86_64-linux/bear@nixos-laptop/default.nix":

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

       error: infinite recursion encountered
       at /nix/store/4r8s42c9mwfvgdlxv0izb1cmlzrsb5nz-source/lib/modules.nix:515:28:
          514|         addErrorContext (context name)
          515|           (args.${name} or config._module.args.${name})
             |                            ^
          516|       ) (functionArgs f);

I am fairly surprised this is happening since the flake is as small as it can get. Just a module, a home configuration file and a system configuration file; here's their contents:

# modules/home/foo/default.nix
{ namespace, lib, ... }:
with lib;
{
    options."${namespace}".foo = {
        enable = mkEnableOption "Foo";
    };
}

# homes/x86_64-linux/bear@nixos-laptop
{ pkgs, lib, namespace, ... }:
{
    "${namespace}".foo.enable = true;
    home.stateVersion = "24.05";
}

# systems/x86_64-linux/nixos-laptop
{ config, namespace, lib, pkgs, ... }:
{
    imports = [./hardware.nix];

    users.users."bear" = {
        isNormalUser = true;
    };

    system.stateVersion = "24.05";
}

# flake.nix
{
    description = "DataMarket's NixOS flake";

    inputs = {
        # Nix Packages
        nixpkgs.url = "github:nixos/nixpkgs/nixos-unstable";

        # Snowfall
        snowfall-lib = {
            url = "github:snowfallorg/lib";
            inputs.nixpkgs.follows = "nixpkgs";
        };

        # Home Manager
        home-manager = {
            url = "github:nix-community/home-manager/release-24.05";
            inputs.nixpkgs.follows = "nixpkgs";
        };
    };

    outputs = inputs: inputs.snowfall-lib.mkFlake {
        inherit inputs;
        src = ./.;

        channels-config = {
            allowUnfree = true;
        };
    };
};

If i change "${namespace}" to a hardcoded internal in the line the module is enabled, it works.

Thanks in advance.

[jakehamilton]

Ah I think this is an issue with using home-manager as a NixOS module. I checked and it looks like that path is the only one that does not pass down namespace. It absolutely should, this is a bug. We pass namespace to everything else, I am pretty sure that I missed this one instance.

https://github.com/snowfallorg/lib/blob/main/snowfall-lib/home/default.nix#L276

More clearly stated: when using home-manager as a NixOS module, home-manager needs to have namespace passed as a specialArg, but Snowfall Lib is not doing that.

[Bear-03]

Ah I see, thanks. Is this planned to be resolved? For now I can just hardcore the namespace, but I'd like to do it the correct way.

[jakehamilton]

It should be fixed in a future release, just depends on me or someone else having the time and energy to implement the change.

[dtgagnon]

@Bear-03

I noticed a few things that don't quite align with @jakehamilton's suspicion, nor the infinite recursion related error. Perhaps there's more at play here then I'm understanding. That said, here's what I noticed:

1. You have this module option declared in the /modules/home/ directory, but you are attempting to enable it in /systems//nixos-laptop/default.nix. In my experience, there appears to be a strong separation between the home modules and the nixos system modules. For example, you declare home modules only in the user homes/<architecture>/<user>@<host>/default.nix file and nixos modules only in the system systems/<architecture>/<host>/default.nix file. I'm pretty sure you'll get an error if you attempt to activate a module across those boundaries, as you appear to have done in your examples. I'm assuming you don't have a modules/nixos/foo/default.nix as well as a modules/home/foo/default.nix file.

# modules/**home/**foo/default.nix
{ namespace, lib, ... }:
 with lib;
 {
     options."${namespace}".foo = {
         enable = mkEnableOption "Foo";
     };
 }

2. I may be ignorant, but I believe this is a typo on the architecture.

# homes/**x64_86-linux**/bear@nixos-laptop **---> The architecture is `x86_64-linux`, is it not?**
 { pkgs, lib, namespace, ... }:
 {
     "${namespace}".foo.enable = true;
     home.stateVersion = "24.05";
 }

# systems/**x64_84-linux**/nixos-laptop  **---> Same architecture typo.**
{ config, namespace, lib, pkgs, ... }:
 {
     imports = [./hardware.nix];
 
     users.users."bear" = {
         isNormalUser = true;
     };
 
     system.stateVersion = "24.05";
 }

3. You're not declaring a specific namespace in your flake. I guess ${namespace} doesn't pass the namespace when it's defaulting to internal? If you declared any namespace here, as shown below, you should be fine using ${namespace} in your configuration modules.

# flake.nix
{
    description = "DataMarket's NixOS flake";

    inputs = {
        # Nix Packages
        nixpkgs.url = "github:nixos/nixpkgs/nixos-unstable";

        # Snowfall
        snowfall-lib = {
            url = "github:snowfallorg/lib";
            inputs.nixpkgs.follows = "nixpkgs";
        };

        # Home Manager
        home-manager = {
            url = "github:nix-community/home-manager/release-24.05";
            inputs.nixpkgs.follows = "nixpkgs";
        };
    };

    outputs = inputs: inputs.snowfall-lib.mkFlake {
        inherit inputs;
        src = ./.;

        **snowfall.namespace = "<some-namespace>"; -----> You're missing a line like this, so the default is being used, which is `internal`, per the documentation. This is why things work when you switch to `internal` in your config.**

        channels-config = {
            allowUnfree = true;
        };
    };
};

[Bear-03]

1. I am not sure what you mean. I am enabling them in homes/x64_86-linux/bear@nixos-laptop, as the comment in the snippet says.

2. My bad, that was indeed a typo I made when writing the issue body. However, in the minimal working example that I tested, that error is not present. I will edit the body so this is clear.

3. I have tried this both with an explicit namespace and the implicit internal namespace and neither of them have worked. Even if that was the case, i don't think it would make sense for "internal" to work any different between nixos and home modules.

[dtgagnon]

1. Yeah my bad, I misread, from what I see you have that correct.

2. I agree that it should work the same for both, and there's apparently a pull request waiting for review and merging that fixes that. On another note, I have gotten the declared namespace to work in both nixos and home modules, but the only thing that I have that's different is both a mkLib and mkFlake part to my output, and the mkLib output declares the custom namespace. Not sure that's intended, cause it's a bit confusing, but this is what works for me.

outputs =
    inputs:
    let
      lib = inputs.snowfall-lib.mkLib {
        inherit inputs;
        src = ./.;
        snowfall = {
          meta = {
            name = "";
            title = "";
          };
          namespace = "";
        };
      };
    in

    lib.mkFlake
      {
        inherit inputs;
        src = ./.;

        channels-config = {
          allowUnfree = true;
          permittedInsecurePackages = [ ];
        };

        ...etc...

[anntnzrb]

Fixed

The namespace argument is now available in home-manager configurations when used as NixOS modules.

Root Cause

When home-manager is used as a NixOS module, the namespace was not being passed to home-manager.extraSpecialArgs, even though it was correctly passed when home-manager is used standalone. This caused infinite recursion when trying to use namespace in home configuration files.

Solution

Added inherit (snowfall-config) namespace; to home-manager.extraSpecialArgs in snowfall-lib/home/default.nix:278.

Usage

You can now use namespace in your home configuration files:

# homes/x86_64-linux/user@host/default.nix
{ namespace, lib, ... }:
{
  "${namespace}".foo.enable = true;
  home.stateVersion = "24.05";
}

And in your home modules:

# modules/home/foo/default.nix
{ namespace, lib, ... }:
with lib;
{
  options."${namespace}".foo = {
    enable = mkEnableOption "Foo";
  };
}

Closes #147
Commit: anntnzrb/snowfall-lib@3d03566