cannot pass in spaces with --add-flags with makeBinaryWrapper

[MrQubo]

Describe the bug

It seems it's impossible to pass argument that contains space with makeBinaryWrapper. With makeShellWrapper it's possible with --add-flags '"a b"'. But makeBinaryWrapper splits it as two arguments "a and b".

User @gerg-l:matrix.org on matrix proposed to add --add-flag to bypass split by space on --add-flags.
I'm guessing it might be @Gerg-L?

Steps To Reproduce

I've made a derivation for testing:

default.nix

{ stdenv, writeTextFile, makeBinaryWrapper  }:

stdenv.mkDerivation {
  name = "example";

  src = writeTextFile {
    name = "example.c";
    text = ''
      #include <stdio.h>

      int main(int argc, const char const * argv[])
      {
        for (int i = 0; i < argc; i += 1) {
          puts(argv[i]);
        }
      }
    '';
  };
  dontUnpack = true;

  nativeBuildInputs = [ makeBinaryWrapper ];

  buildPhase = ''
    gcc $src -o example
  '';

  installPhase = ''
    install -D example -t $out/bin/
    wrapProgram $out/bin/example --add-flags '"a b"'
  '';

}

shell.nix

with import <nixpkgs> {};

let
  example = pkgs.callPackage ./default.nix {};

in
pkgs.mkShell {
  packages = [ example ];
}

Run with nix-shell --run example.

Expected behaviour

It should be possible to add/append spaces as arguments to wrapped program.

Notify maintainers

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[Gerg-L]

Yup it was me

[eclairevoyant]

Basically this is a limitation when we don't use __structuredAttrs.
See #114044 for a similar issue.

[MrQubo]

Hmm, we could add --add-flag as a workaround for now, but maybe it's better to wait for #318614.

[eclairevoyant]

Can you give an example of why this would be useful?

[MrQubo]

Whenever you need to overwrite some cli arguments and those arguments contain spaces.
E.g. of arguments that could contain spaces are space-delimited lists or shell commands.

[Gerg-L]

Basically this is a limitation when we don't use __structuredAttrs

i don't understand how __structuredAttrs would matter at all here
maybe when using wrapGAppsHook or similar, but not when using raw wrapProgram in the postInstall

[MrQubo]

You're right, it doesn't matter for the current implementation. Though, with structuredAttrs we could implement makeWrapper differently, using derivation arguments. E.g.

stdenv.mkDerivation {
...
wrapPrograms = [
  {
    path = "bin/example";
    addFlags = [ "--cmd" "foo bar" ];
  }
];
}