Unable to patch binary in Python environment with uv

[dmarcoux]

In another issue, I wrote about how to patch the ruff binary in a Python virtual environment relying on venv.

This was my devenv.nix:

  (...)

  languages.python = {
    enable = true;
    version = "3.12.7";
    venv = {
      enable = true;
      requirements = ./requirements.txt;
    };
  };

  tasks = {
    # Patch ruff to make it runnable
    "venv:patchelf" = {
      exec = "${lib.getExe pkgs.patchelf} --set-interpreter ${pkgs.stdenv.cc.bintools.dynamicLinker} $VIRTUAL_ENV/bin/ruff";
      after = [ "devenv:python:virtualenv" ]; # Runs after this
      before = [ "devenv:enterShell" ]; # Runs before this
    };
  };

Since then, I've migrated to uv and I am now unable to patch the ruff binary. devenv.nix is now like this:

(...)

  languages.python = {
    enable = true;
    version = "3.12.7";
    # Enable uv, an extremely fast Python package and project manager - https://docs.astral.sh/uv/
    uv = {
      enable = true;
      package = pkgs-unstable.uv;
      # Sync the project's dependencies (from `pyproject.toml`) with the virtual environment
      sync.enable = true;
    };
    # Enable Python virtual environment. It's created with `uv venv`.
    venv.enable = true;
  };

  tasks = {
    "venv:patchelf-ruff" = {
      description = "Patch ruff binary. It is dynamically linked to ld, which will not work with Nix";
      exec = "${lib.getExe pkgs.patchelf} --set-interpreter ${pkgs.stdenv.cc.bintools.dynamicLinker} $VIRTUAL_ENV/bin/ruff";
      after = [ "devenv:python:uv" ]; # Our task runs after this
      before = [ "devenv:enterShell" ]; # Our task runs before this
    };
  };

I don't know why, but I cannot execute the ruff binary anymore. uv run ruff errors out with cannot execute binary file. Executing ruff directly (it's in the $PATH), results in zsh: exec format error: ruff.

So somehow, setting up the Python virtual environment with uv changes something... but what exactly?

Thank you for your help!