After d95261b435, the following flake.nix fails:
```nix
{
inputs.nixpkgs.url = "github:NixOS/nixpkgs/nixos-unstable";
outputs = { nixpkgs, ... }: {
nixosConfigurations.demo = nixpkgs.lib.nixosSystem {
system = "x86_64-linux";
modules = [
({ lib, ... }: {
boot.loader.grub.enable = false;
fileSystems."/" = { device = "none"; fsType = "tmpfs"; };
nixpkgs.config.packageOverrides =
lib.mkIf false (_: { });
})
];
};
};
}
```
This is the error:
```
$ nix build /tmp/tmp.vWEVitTgK9/#nixosConfigurations.demo.config.system.build.toplevel
evaluation warning: system.stateVersion is not set, defaulting to 26.05. Read why this matters on https://nixos.org/manual/nixos/stable/options.html#opt-system.stateVersion.
error:
… while calling the 'derivationStrict' builtin
at <nix/derivation-internal.nix>:37:12:
36|
37| strict = derivationStrict drvAttrs;
| ^
38|
… while evaluating derivation 'nixos-system-nixos-26.05.20260409.4c1018d'
whose name attribute is located at /nix/store/anvdcc2arw7kqrvwnidvhw6ypkkvws68-source/pkgs/stdenv/generic/make-derivation.nix:541:11
… while evaluating attribute 'buildCommand' of derivation 'nixos-system-nixos-26.05.20260409.4c1018d'
at /nix/store/anvdcc2arw7kqrvwnidvhw6ypkkvws68-source/nixos/modules/system/activation/top-level.nix:64:7:
63| passAsFile = [ "extraDependencies" ];
64| buildCommand = systemBuilder;
| ^
65|
… while evaluating the option `environment.etc.dbus-1.source':
… while evaluating the default value of option `pythonTestDriverPackage`
… while evaluating the module argument `hostPkgs' in "/nix/store/anvdcc2arw7kqrvwnidvhw6ypkkvws68-source/nixos/lib/testing/driver.nix":
… noting that argument `hostPkgs` is not externally provided, so querying `_module.args` instead, requiring `config`
… while evaluating the option `hostPkgs':
(stack trace truncated; use '--show-trace' to show the full, detailed trace)
error: The option `hostPkgs' was accessed but has no value defined. Try setting the option.
```
Setting a `defaultText` fixes the issue.
I've also added a regression test under `nixos/tests/nixos-test-driver/` and
fixed a typo in the option description ("implemetnation").
8e5d6f456d