nix flake show shows darwinConfigurations: unknown

[diktomat]

When using nix-darwin in a flake, nix flake show doesn't know how to display darwin configurations, and instead shows unknown. Compared with nixos configurations:

{
  outputs = {darwin, nixpkgs}: {
    darwinConfigurations.<hostname> = darwin.lib.darwinSystem {<omitted>};
    nixosConfigurations.<hostname> = nixpkgs.lib.nixosSystem {<omitted>};
  }
}

❯ nix flake show
git+file:///foo
├───darwinConfigurations: unknown
└───nixosConfigurations
    └───<hostname>: NixOS configuration

[reckenrode]

This is a Nix limitation. nix flake show only knows how to display certain outputs (e.g., packages and nixosConfigurations), and it’s not currently extensible.

There is an open issue (NixOS/nix#6454) about adding extensibility, but a desire was expressed for a different approach than the one proposed. There is also an issue (NixOS/nix#6257) about making the output schema more flexible regarding modules and configurations, which would allow Nix to know about e.g., nix-darwin configurations (for nix flake check but presumably also nix flake show).

[roberth]

Regardless of plans for genericity (thanks @reckenrode for linking) this specific case has been solved for nix flake check since Nix 2.13:

• flake check: Recognize well known community attributes NixOS/nix#7606

EDIT: nix flake show does not recognize this yet, but nix flake check does handle it.

[Enzime]

Closing this as this is an upstream issue

We might reopen it if this PR ever gets merged NixOS/nix#8892