Fix #7272 - Allow users to override importsArgs in eval-config.nix.

[nbp]

These changes renames the lib.evalModules argument attribute from specialArgs into importsArgs, to represent the actual use of this argument. Also, this change modify nixos lib/eval-config.nix to expose this argument and to use it to override the default set of arguments defined in this file.

This would solve the issue #7272, by renaming extraArgs into importsArgs. The difference between the 2 arguments is that extraArgs is now evaluated as _module.args, and importsArgs is for arguments which are used for the resolution of imports attributes value.

cc @edolstra , @shlevy

[wizeman]

Could you tell me how this fixes #7272?

I've tried applying your commit and then evaluating the following configuration:

{ config, pkgs, lib, hydra_path, ... }:

{
  _module.importsArgs.hydra_path = lib.mkDefault "/root/src/localrepos/hydra";

  imports = [
    "${hydra_path}/hydra-module.nix"
  ];
}

... but this fails with:

error: while evaluating the attribute ‘config.system.build.toplevel’ at /nixdev/nixpkgs/nixos/lib/eval-config.nix:54:5:
while evaluating the attribute ‘config’ at /nixdev/nixpkgs/lib/modules.nix:86:25:
while evaluating ‘yieldConfig’ at /nixdev/nixpkgs/lib/modules.nix:73:29, called from /nixdev/nixpkgs/lib/modules.nix:72:16:
while evaluating ‘mergeModules’ at /nixdev/nixpkgs/lib/modules.nix:164:26, called from /nixdev/nixpkgs/lib/modules.nix:63:17:
while evaluating ‘mergeModules'’ at /nixdev/nixpkgs/lib/modules.nix:168:36, called from /nixdev/nixpkgs/lib/modules.nix:165:5:
while evaluating ‘concatMap’ at /nixdev/nixpkgs/lib/lists.nix:54:18, called from /nixdev/nixpkgs/lib/modules.nix:204:9:
while evaluating ‘fold’ at /nixdev/nixpkgs/lib/lists.nix:20:19, called from /nixdev/nixpkgs/lib/modules.nix:63:38:
while evaluating ‘fold'’ at /nixdev/nixpkgs/lib/lists.nix:23:15, called from /nixdev/nixpkgs/lib/lists.nix:27:8:
while evaluating ‘closeModules’ at /nixdev/nixpkgs/lib/modules.nix:90:27, called from /nixdev/nixpkgs/lib/modules.nix:58:16:
while evaluating anonymous function at /nixdev/nixpkgs/lib/modules.nix:92:49, called from /nixdev/nixpkgs/lib/lists.nix:49:19:
infinite recursion encountered

When trying the old way:

{ config, pkgs, lib
, hydra_path ? "/root/src/localrepos/hydra"
, ... }:

{
  imports = [
    "${hydra_path}/hydra-module.nix"
  ];
}

... it also fails with infinite recursion.

What am I doing wrong?

[nbp]

@wizeman,

Basically, this would work the same way as you described in #7272 (comment) , except that instead of having an argument named extraArgs it would be named importsArgs, in your release.nix file:

 1 {
 2   wizynet
 3 , hydra_path
 4 , rg_path
 5 , wizytests_path
 6 , kodiOffPath
 7 , nixpkgs
 8 }:
 9 
10 let
11 
12   pkgs = import nixpkgs { };
13 
14   eval = modules: (import <nixpkgs/nixos/lib/eval-config.nix> {
15     inherit modules;
16     importsArgs = {
17       inherit hydra_path rg_path wizytests_path kodiOffPath;
18     };
19   });

Also, I recall @edolstra mentioning that hydra updates NIX_PATH environment variable with the path of the project inputs, such that you should be able to use <hydra_path> in your import statements. If this alternative works for you, this would avoid landing the current fix.

[wizeman]

Right, I understand how the release.nix file would look like (the file evaluated by Hydra which overrides the default values), but how would the individual config-*.nix files declare and use arguments with default values?

The point of having the default values was so that I could directly evaluate (e.g.) config-wizylap.nix locally using nixos-rebuild switch or nixops deploywithout having to manually specify those values.

[domenkozar]

@nbp what's the status of this?

[nbp]

@wizeman ,
Right, this only solve a problem which is that we can set default values from out-side NixOS, so the current patch does not solve the issue, and I originaly thought that the issue was related to the modulePaths, which as it got reverted made me accidentally thought that this was fixed, but this is not.

I suggested an alternative in #7272 (comment) which I think might work for your use case, if you were to separate the module arguments from the paths arguments.

@domenkozar Thanks for pinging.

[nbp]

Note, #11106 should solve this problem without the need of adding extra arguments to modules, by importing the configuration with nixos.extraModules option. The idea then would be that you define the paths as options in one special module that you include everywhere, and then do the following:

{ config, lib, ... }:

with lib;
{
  options = {
    customImports.hydra_path = mkOption { default = "/root/src/localrepos/hydra"; };
    …
  };

  config = {
    nixos.path = <nixos>;
    nixos.extraModules = with config.customImports; [ hydra_path rg_path wizytests_path kodiOffPath ];
  };
}

This module will basically re-evaluate NixOS with the additional extra modules as-if they were dynamic-imports.

[nbp]

Closing as this issue is solved by #11106.