psycopg-pool extra is silently ignored

[genevieve-me]

I just tried packaging a python tool with pyproject.nix, and am running into some issues with psycopg-pool. It's a standalone package on pypi, but I pull it in as an extra: "psycopg[pool]~=3.1" under [dependencies] in pyproject.toml.

In nixpkgs, this package is under pkgs.python3Packages.psycopg.optional-dependencies.pool. When I was previously building this tool with pkgs.python3Packages.buildPythonApplication, I had something like:

    propagatedBuildInputs = with pkgs.python3Packages; [
      psycopg
      psycopg.optional-dependencies.pool
    ];

However, the following flake produces a python environment without psycopg-pool via nix develop, or a package that fails with ModuleNotFoundError for psycopg_pool when run after nix build:

{
  inputs.nixpkgs.url = "github:nixos/nixpkgs/nixos-unstable";
  inputs.pyproject-nix.url = "github:nix-community/pyproject.nix";
  inputs.pyproject-nix.inputs.nixpkgs.follows = "nixpkgs";

  outputs =
    { nixpkgs, pyproject-nix, ... }:
    let
      project = pyproject-nix.lib.project.loadPyproject { projectRoot = ./.; };
      pkgs = nixpkgs.legacyPackages.x86_64-linux;
      python = pkgs.python3;
    in
    {
      devShells.x86_64-linux.default =
        let
          arg = project.renderers.withPackages {
            inherit python;
          };
          pythonEnv = python.withPackages arg;
        in
        pkgs.mkShell { packages = [ pythonEnv ]; };

      packages.x86_64-linux.default =
        let
          attrs = project.renderers.buildPythonPackage { inherit python; extras = [ "dev" ]; };
        in
        python.pkgs.buildPythonPackage (attrs);
    };
}

What's odd is that if I add a pypi package that's not in nixpkgs to my pyproject.toml dependencies, the build fails with (for example) error: attribute 'ural' missing, which makes complete sense. I didn't see any code in pyproject.nix that would translate psycopg-pool into psycopg.optional-dependencies.pool, so I'm not sure why this is failing silently instead of loudly. (If I add psycopg-pool to my dependencies in pyproject.toml, it does fail in this way).

(PS: This tool is a lifesaver, thanks for your work on it!)

[genevieve-me]

This one might be user error, but I also have a followup question: in order to work around this, I changed my pyproject.toml to include "psycopg-pool>=3.1",, and changed the above flake.nix
to include

      # removed: python = pkgs.python3;
      python = pkgs.python3.override {
        packageOverrides = self: super: {
          psycopg-pool = pkgs.python3Packages.psycopg.optional-dependencies.pool;
        };
      };

Now my build fails during pythonRuntimeDepsCheck with psycopg-pool>=3.1 not satisfied by version 3.1.10.dev1. I'm confused by this, since nixos-unstable is on version 3.1.17 (and as far as I could tell in the commit history, 3.1.10.dev1 was never in nixpkgs) - would appreciate if someone could shed some light on what's happening there.

(Plus, potentially relevant side note to the original issue - in my testing it seems the [pool] extra for psycopg gets totally ignored no matter what I do, which is surprising).