Error description for option conflicts

[danbst]

Issue description

I think, that error description for module options conflict is not newbie friendly. At least it should mention the ways to solve this conflict, e.g. lib.mkForce or lib.mkOverride. For example, you cannot set this option

Steps to reproduce

module1:

{ networking.firewall.enable = true; }

module2:

{
   imports = [ ./module1.nix ];
   networking.firewall.enable = false;
}

results into

building Nix...
building the system configuration...
error: The option `networking.firewall.enable' has conflicting definitions, in `/etc/nixos/services/module.nix' and `<unknown-file>'.
(use ‘--show-trace’ to show detailed location information)

Example 2: one-liner

  containers.t.config.imports = [ <nixpkgs/nixos/modules/virtualisation/amazon-image.nix> ];

building Nix...
building the system configuration...
error: The unique option `containers.t.networking.hostName' is defined multiple times, in `/nix/store/28wbqc87ygsm1h1zzim2w843fa35iyz4-nixexprs.tar.xz/nixos/modules/virtualisation/amazon-image.nix' and `<unknown-file>'.

Technical details

• System: 16.03.858.b8d7324 (Emu)

[Profpatsch]

cc @nbp

[nbp]

Thanks for the report, about the fact that NixOS error messages do not describe any way to solve the issue which is reported.

I will look into it.

[davidak]

Sometimes it even don't describe where the issue is, like:

error: The unique option `containers.target0.networking.hostName' is defined multiple times, in `<unknown-file>' and `<unknown-file>'.

I would consider <unknown-file> a bug since Nix should know where the conflict is.

My code:

configuration.nix

{ config, pkgs, ... }:

let
  target = import ../gvm-test-target-container/configuration.nix;
in
{
...
  containers = {
    target0 = {
      config = target;
    };
  };

../gvm-test-target-container/configuration.nix

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

{ boot.isContainer = true;
  networking.hostName = mkDefault "foo";
  networking.useDHCP = false;
  networking.firewall.enable = false;
...
}

[stale]

Thank you for your contributions.

This has been automatically marked as stale because it has had no activity for 180 days.

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[samuela]

It would still be helpful to get a more actionable error message here. In particular something pointing users towards mkForce, mkOverride, etc.

[stale]

I marked this as stale due to inactivity. → More info

[samuela]

Still an issue.

[stale]

I marked this as stale due to inactivity. → More info

[montchr]

Still an issue, yes. I found my way to this issue while looking for advice about tracking down an <unknown-file>. Better advice around resolving option conflicts is one thing, but <unknown-file> feels to me like it compounds upon the issue even further.

[bobvanderlinden]

I think this is solved by #62712, b3cc29c and fe734ef