Nix flake only works within devShell: how to bind python package to writeScriptShellBin

Question

So my school has a coding style, and thus a program checking it's compliance.

Recently they added libclang as a dependency of the python environment to their tool. Only problem is, this env is managed by banana-vera using boost, which i succesfully ported to nix so time ago.

So i have a flake:

{
  inputs = {
    nixpkgs.url = "github:NixOS/nixpkgs/nixos-unstable";
    ruleset.url = "git+ssh://git@github.com/Epitech/banana-coding-style-checker.git";
    ruleset.flake = false;
    flake-utils.url = "github:numtide/flake-utils";
  };
  outputs = { self, nixpkgs, ruleset, flake-utils, ... }@inputs:
    flake-utils.lib.eachDefaultSystem
      (system:
        let pkgs = nixpkgs.legacyPackages.${system}; in
        rec {
          packages = flake-utils.lib.flattenTree rec {
            report = (pkgs.writeShellScriptBin "cs" ''
              custom script, running `${pkgs.banana-vera}/bin/vera++ --profile epitech --root ${ruleset}/vera`
            '');
            default = report;
          };

          apps.report.type = "app";
          apps.report.program = "${packages.report}/bin/cs";
          apps.default = apps.report;
        });
}

So i thought at first i could just override the python env banana = pkgs.banana-vera.overrideAttrs { buildInputs = pkgs.banana-vera.buildInputs ++ [ pkgs.libclang ]; } which didn't worked.

I realized that libclang is not the same as the one provided by nixpkgs, and thus made a build for it:

libclangpy = p: p.buildPythonPackage rec {
  pname = "libclang";
  version = "16.0.6";
  format = "wheel";

    src = p.fetchPypi {
      inherit pname version format;
      platform = "manylinux2010_x86_64";
      hash = "sha256-nc3HMJOXiLi2n/1tXXX+U2bj7gB/Hjapl5nsCwwAFJI=";
    };
  };

  pyenv = pkgs.python310.withPackages (p: [ (libclangpy p) ]);
  banana = pkgs.banana-vera.override { python310 = pyenv; };

Which didn't worked either...

At this point, i tried to setup a devShell just to see if the package clang.cindex was installed.

devShells.default = pkgs.mkShell {
  packages = [ pyenv ];
};

Turns out, this worked, and clang.cindex, can be imported from the python env given by the devshell. However, trying to build or run the cs script, and it dosn't work.

So, i tried to build it within the shell, and then it finds the package..? Maybe it could be a propagatedInput then,

banana = pkgs.banana-vera.overrideAttrs {
  propagatedBuildInputs = [ libclangpy ];
};

nope.

Finally i tried this, along some variations of it

banana = pkgs.symlinkJoin {
  name = "banana-patched";
  paths = [ pkgs.banana-vera ];
  nativeBuildInputs = [ pkgs.makeWrapper ];
  postPatch = ''
    wrapProgram $out/bin/vera++ --prefix PYTHONPATH : ${pyenv} 
  '';
};

But it doesn't work either I have tried all the thing i can think of, and yet no result. If anyone have an idea to fix this program