editablePackageSources doesn't work for packages in a src directory

[MartinEekGerhardsen]

Describe the issue

When a package is in a src directory, the editablePackageSources attribute doesn't work.

Additional context

Set up a package app in the main directory, with a single __init__.py file:

def main():
    print("test")

If the flake.nix and pyproject.toml files are set up like this:

default.nix/shell.nix/flake.nix:

{
  description = "Application packaged using poetry2nix";

  inputs = {
    flake-utils.url = "github:numtide/flake-utils";
    nixpkgs.url = "github:NixOS/nixpkgs/nixos-unstable-small";
    poetry2nix = {
      url = "github:nix-community/poetry2nix";
      inputs.nixpkgs.follows = "nixpkgs";
    };
  };

  outputs = { self, nixpkgs, flake-utils, poetry2nix }:
    flake-utils.lib.eachDefaultSystem (system:
      let
        pkgs = nixpkgs.legacyPackages.${system};
        inherit (poetry2nix.lib.mkPoetry2Nix { inherit pkgs; }) mkPoetryEnv;

      in
      {
        packages.myapp-env = mkPoetryEnv {
          projectDir = self;
          editablePackageSources.app = ./.;
        };
        devShells.default = pkgs.mkShell {
          inputsFrom = [ self.packages.${system}.myapp-env.env ];
        };
      });
}

pyproject.toml:

[tool.poetry]
name = "app"
version = "0.1.0"
description = ""
authors = ["Your Name <you@example.com>"]
license = "MIT"
readme = "README.md"

[tool.poetry.scripts]
testing = "app:main"

[tool.poetry.dependencies]
python = "^3.11"

[build-system]
requires = ["poetry-core"]
build-backend = "poetry.core.masonry.api"

poetry.lock:

# This file is automatically @generated by Poetry 1.6.1 and should not be changed by hand.
package = []

[metadata]
lock-version = "2.0"
python-versions = "^3.11"
content-hash = "81b2fa642d7f2d1219cf80112ace12d689d053d81be7f7addb98144d56fc0fb2"

The result is that changing the main function in app/__init__.py will change the behaviour of the testing script (within the devshell defined in the flake).

If this app package is moved to a src folder, and the following changes are applied to the flake.nix and pyproject.toml files, this behaviour is lost, and only recompiling the project will apply the changes. The only changes are changing the editablePackageSources.app attribute from ./. to ./src in the flake.nix file, and adding packages = [{include="app", from="src}] to the [tool.poetry] field of the pyproject.toml file:

default.nix/shell.nix/flake.nix:

{
  description = "Application packaged using poetry2nix";

  inputs = {
    flake-utils.url = "github:numtide/flake-utils";
    nixpkgs.url = "github:NixOS/nixpkgs/nixos-unstable-small";
    poetry2nix = {
      url = "github:nix-community/poetry2nix";
      inputs.nixpkgs.follows = "nixpkgs";
    };
  };

  outputs = { self, nixpkgs, flake-utils, poetry2nix }:
    flake-utils.lib.eachDefaultSystem (system:
      let
        pkgs = nixpkgs.legacyPackages.${system};
        inherit (poetry2nix.lib.mkPoetry2Nix { inherit pkgs; }) mkPoetryEnv;

      in
      {
        packages.myapp-env = mkPoetryEnv {
          projectDir = self;
          editablePackageSources.app = ./src;
        };
        devShells.default = pkgs.mkShell {
          inputsFrom = [ self.packages.${system}.myapp-env.env ];
        };
      });
}

pyproject.toml:

[tool.poetry]
name = "app"
version = "0.1.0"
description = ""
authors = ["Your Name <you@example.com>"]
license = "MIT"
readme = "README.md"
packages = [
    {include = "app", from = "src"},
]

[tool.poetry.scripts]
testing = "app:main"

[tool.poetry.dependencies]
python = "^3.11"

[build-system]
requires = ["poetry-core"]
build-backend = "poetry.core.masonry.api"

poetry.lock:

# This file is automatically @generated by Poetry 1.6.1 and should not be changed by hand.
package = []

[metadata]
lock-version = "2.0"
python-versions = "^3.11"
content-hash = "81b2fa642d7f2d1219cf80112ace12d689d053d81be7f7addb98144d56fc0fb2"