nix run error when trying to run an "app" from file with -f flag (in non-flake project)

[adrian-gierakowski]

Describe the bug

Given following my-apps.nix file:

let
  pkgs = import (builtins.fetchTarball "https://github.com/nixos/nixpkgs/archive/ff0dbd94265ac470dda06a657d5fe49de93b4599.tar.gz") {};
in {
  hello = {
    type = "app";
    program = "${pkgs.hello}/bin/hello";
  };
}

running:

 nix run -f my-apps.nix hello

results in an errer:

error: attribute '' should have type 'derivation'

Steps To Reproduce

see above

Expected behavior

the hello program should be ran, leading to following output:

Hello, world!

nix-env --version output

nix-env (Nix) 2.21.1

Additional context

Priorities

Add 👍 to issues you find important.