Answering my own question a bit, it seems like the example does do exactly that:

https://github.com/nix-community/poetry2nix/blob/0a4d87e50f4eb58e04a4fe48692148196dc04501/templates/app/flake.nix#L41

To be honest I saw it, but I am not sure hot to leverage it in my case.

Gunicorn is ran through a python script calling Popen.

I saw it, but I am not sure hot to leverage it in my case.

Gunicorn is ran through a python script calling Popen.

Hello, we are trying to build pendulum-3.0.0

Without any overrides, we get the following error:
ModuleNotFoundError: No module named 'maturin'
With this override:
buildInputs = (old.buildInputs or [ ]) ++ [ self.maturin ];

We also get the same error.
Searching the code of poetry2nix, we find out some references to maturin, so we did the following override:

pendulum = super.pendulum.overridePythonAttrs (
            old: {
              nativeBuildInputs = (old.nativeBuildInputs or [ ]) ++ [
                pkgs.cargo
                pkgs.rustc
                pkgs.maturin
                # pkgs.rustPlatform.cargoSetupHook
                pkgs.rustPlatform.maturinBuildHook
              ];
              buildInputs = (old.buildInputs or [ ]) ++ [ self.maturin ];
            }
          );

  Now the error is the following:

Executing maturinBuildHook
++ env CC_X86_64_UNKNOWN_LINUX_GNU=/nix/store/62zpnw69ylcfhcpy1di8152zlzmbls91-gcc-wrapper-13.3.0/bin/cc CXX_X86_64_UNKNOWN_LINUX_GN>
error: no matching package named pyo3 found
location searched: registry crates-io
required by package _pendulum v3.0.0 (/build/pendulum-3.0.0/rust)
As a reminder, you're using offline mode (--offline) which can sometimes cause surprising resolution failures, if this error is too >
💥 maturin failed
Caused by: Cargo metadata failed. Does your crate compile with cargo build?
Caused by: cargo metadata exited with an error:

We are out of ideas.

Any ideas?

Ok so using this in my flake :

Ok so using this in my flake :

     in
        {
        packages = {
          default = lookylooApp.dependencyEnv;
        };

make gunicorn available at ./result/bin.
Running gunicorn manualy (without the Popen but from my shell) is working.

I think the problem might come from the python script with a Popen calling gunicorn but "not the gunicorn from my flake"

How can I force the script to use the "generated" gunicorn ?

Should I replace the exe inside the python script ?
Should I update the PATH env, and how ?

I did found a solution :

{
  description = "Application packaged using poetry2nix";

  inputs = {
    nixpkgs.url = "github:NixOS/nixpkgs/nixos-unstable";
    flake-utils = {
      url = "github:numtide/flake-utils";
    };
    poetry2nix = {
      #url = "github:nix-community/poetry2nix";
      url = "git+https://gitea.com/oven_spinout988/poetry2nix";
      inputs.nixpkgs.follows = "nixpkgs";
    };
  };

  outputs = { self, nixpkgs, flake-utils, poetry2nix }:
    flake-utils.lib.eachDefaultSystem
    (system:
    let

      [...]

      lookylooApp = let
        lookylooApp = pkgs.poetry2nix.mkPoetryApplication
          {
            inherit projectDir;
            inherit propagatedBuildInputs;
            overrides = p2n-overrides;
          };
        in lookylooApp.overrideAttrs (old: {
          postInstall = (if lookylooApp ? old then old else '''') + ''
            substituteInPlace $out/lib/${lookylooApp.python.executable}/site-packages/bin/start_website.py \
            --replace "gunicorn" "${lookylooApp.dependencyEnv}/bin/gunicorn"
          '';
        });
    in
      {
        packages = {
          default = lookylooApp;
        };
      };
}

Please let me know if the code can be improved

I did found a solution :

{
  description = "Application packaged using poetry2nix";

  inputs = {
    [...]
  };

  outputs = { self, nixpkgs, flake-utils, poetry2nix }:
    flake-utils.lib.eachDefaultSystem
    (system:
    let

      [...]

      lookylooApp = let
        lookylooApp = pkgs.poetry2nix.mkPoetryApplication
          {
            inherit projectDir;
            inherit propagatedBuildInputs;
            overrides = p2n-overrides;
          };
        in lookylooApp.overrideAttrs (old: {
          postInstall = (if lookylooApp ? old then old else '''') + ''
            substituteInPlace $out/lib/${lookylooApp.python.executable}/site-packages/bin/start_website.py \
            --replace "gunicorn" "${lookylooApp.dependencyEnv}/bin/gunicorn"
          '';
        });
    in
      {
        packages = {
          default = lookylooApp;
        };
      };
}

Please let me know if the code can be improved

class StandaloneApplication(gunicorn.app.base.BaseApplication):
    def __init__(self, app, options=None):
        self.options = options or {}
        self.application = app
        super().__init__()

    def load_config(self):
        config = {
            key: value
            for key, value in self.options.items()
            if key in self.cfg.settings and value is not None
        }
        for key, value in config.items():
            self.cfg.set(key.lower(), value)

    def load(self):
        return self.application

Hey, I'm having an issue with getting pytorch to build. I have a minimal config which works fine:
https://github.com/volkswagenfeature/minimalTorchRocm/tree/a9c7cd346e3a2493cc20489407df0d1f59d82d9f

But once I add pytorch, there's a null somewhere it shouldn't be:
https://github.com/volkswagenfeature/minimalTorchRocm/commit/acf99457e810777a8316c26e69a0b281f0c0945e

Now nix run fails with

warning: Git tree '/home/tristan/Projects/nixos/minimal-replication/minimalTorchRocm' is dirty
error:
       … while calling the 'derivationStrict' builtin

         at /builtin/derivation.nix:9:12: (source not available)

       … while evaluating derivation 'python3-3.12.4-env'
         whose name attribute is located at /nix/store/qxf6anli54ij0q1sdlnlgx9hyl658a4v-source/pkgs/stdenv/generic/make-derivation.nix:334:7

       … while evaluating attribute 'passAsFile' of derivation 'python3-3.12.4-env'

         at /nix/store/qxf6anli54ij0q1sdlnlgx9hyl658a4v-source/pkgs/build-support/trivial-builders/default.nix:69:9:

           68|         inherit buildCommand name;
           69|         passAsFile = [ "buildCommand" ]
             |         ^
           70|           ++ (derivationArgs.passAsFile or [ ]);

       (stack trace truncated; use '--show-trace' to show the full trace)

       error: value is null while a set was expected