[doc] Which parameters do nix-build and nix-instatiate pass when evaluating a derivation?

Help
1

I copied and adapted an example from the documentation on how to use the fetchGit fetcher.

{ stdenv, fetchgit }:

stdenv.mkDerivation {
  name = "simple-dlna-browser";
  src = fetchgit {
    url = "https://github.com/javier-lopez/learn.git";
    sparseCheckout = [
      "sh/tools/simple-dlna-browser"
    ];
    sha256 = "0000000000000000000000000000000000000000000000000000";
  };
  installPhase = ''
    mkdir $out/bin
    chmod +x sh/tools/simple-dlna-browser
    cp sh/tools/simple-dlna-browser $out/bin/
  '';
}

But it fails

$ nix-build simple-dlna-browser.nix 
error: cannot evaluate a function that has an argument without a value ('stdenv')

       Nix attempted to evaluate a function as a top level expression; in
       this case it must have its arguments supplied either by default
       values, or passed explicitly with '--arg' or '--argstr'. See
       https://nixos.org/manual/nix/stable/expressions/language-constructs.html#functions.

       at /home/nixos/nixos/derivations/scripts/simple-dlna-browser.nix:1:3:

            1| { stdenv, fetchgit }:
             |   ^
            2|

So I went to the nix-build documentation and nix-instantiate documentation, but it doesn’t explain which parameters it passes when evaluating the expression. I assume pkgs but what else? Is this documented somewhere?

2

It doesn’t pass any parameters unless specifically given on the command line, it just passes an empty attrset if the file contains a function.

For a derivation file formatted for callPackage like this, you’ll need to invoke that, either on the command line or with a default.nix to glue it together for nix-build:
nix-build -E '(import <nixpkgs> {}).callPackage ./foo.nix {}'

1 Like
3

Thanks. I create an issue on github to improve the documentation: nix-build is missing which parameters is passes expressions · Issue #7544 · NixOS/nix · GitHub