migrate from poetry2nix to uv2nix

Author: juliankuners

{{cookiecutter.project_slug}}/flake.nix

@@ -3,39 +3,80 @@
   inputs = {
     nixpkgs.url = "nixpkgs/nixos-unstable";
     flake-utils.url = "github:numtide/flake-utils";
-    poetry2nix.url = "github:nix-community/poetry2nix";
+    pyproject-nix = {
+      url = "github:pyproject-nix/pyproject.nix";
+      inputs.nixpkgs.follows = "uv2nix/nixpkgs";
+      # inputs.uv2nix.follows = "nixpkgs";
+    };
+    pyproject-build-systems = {
+      url = "github:pyproject-nix/build-system-pkgs";
+      inputs.pyproject-nix.follows = "pyproject-nix";
+      inputs.uv2nix.follows = "uv2nix";
+      inputs.nixpkgs.follows = "uv2nix/nixpkgs";
+      # inputs.uv2nix.follows = "nixpkgs";
+    };
+    uv2nix = {
+      url = "github:pyproject-nix/uv2nix";
+      inputs.pyproject-nix.follows = "pyproject-nix";
+      # stale nixpkgs is missing the alias `lib.match` -> `builtins.match`
+      # therefore point uv2nix to a patched nixpkgs, which introduces this alias
+      # this is a temporary solution until nixpkgs us up-to-date again
+      inputs.nixpkgs.url = "github:runtimeverification/nixpkgs/libmatch";
+      # inputs.uv2nix.follows = "nixpkgs";
+    };
   };
-  outputs = { self, nixpkgs, flake-utils, poetry2nix }:
-    let
-      allOverlays = [
-        poetry2nix.overlay
-        (final: prev: {
-          {{ cookiecutter.project_slug }} = prev.poetry2nix.mkPoetryApplication {
-            python = prev.python310;
-            projectDir = ./.;
-            groups = [];
-            # We remove `dev` from `checkGroups`, so that poetry2nix does not try to resolve dev dependencies.
-            checkGroups = [];
-           };
-        })
-      ];
-    in flake-utils.lib.eachSystem [
+  outputs = { self, nixpkgs, flake-utils, pyproject-nix, pyproject-build-systems, uv2nix }:
+  let
+    pythonVer = "310";
+  in flake-utils.lib.eachSystem [
       "x86_64-linux"
       "x86_64-darwin"
       "aarch64-linux"
       "aarch64-darwin"
     ] (system:
-      let
-        pkgs = import nixpkgs {
-          inherit system;
-          overlays = allOverlays;
+    let
+      # due to the nixpkgs that we use in this flake being outdated, uv is also heavily outdated
+      # we can instead use the binary release of uv provided by uv2nix for now
+      uvOverlay = final: prev: {
+        uv = uv2nix.packages.${final.system}.uv-bin;
+      };
+      {{ cookiecutter.project_slug }}Overlay = final: prev: {
+        {{ cookiecutter.project_slug }} = final.callPackage ./nix/{{ cookiecutter.project_slug }} {
+          inherit pyproject-nix pyproject-build-systems uv2nix;
+          python = final."python${pythonVer}";
         };
-      in {
-        packages = rec {
-          inherit (pkgs) {{ cookiecutter.project_slug }};
-          default = {{ cookiecutter.project_slug }};
+      };
+      pkgs = import nixpkgs {
+        inherit system;
+        overlays = [
+          uvOverlay
+          {{ cookiecutter.project_slug }}Overlay
+        ];
+      };
+      python = pkgs."python${pythonVer}";
+    in {
+      devShells.default = pkgs.mkShell {
+        name = "uv develop shell";
+        buildInputs = [
+          python
+          pkgs.uv
+        ];
+        env = {
+          # prevent uv from managing Python downloads and force use of specific 
+          UV_PYTHON_DOWNLOADS = "never";
+          UV_PYTHON = python.interpreter;
         };
-      }) // {
-        overlay = nixpkgs.lib.composeManyExtensions allOverlays;
+        shellHook = ''
+          unset PYTHONPATH
+        '';
+      };
+      packages = rec {
+        inherit (pkgs) {{ cookiecutter.project_slug }};
+        default = {{ cookiecutter.project_slug }};
+      };
+    }) // {
+      overlays.default = final: prev: {
+        inherit (self.packages.${final.system}) {{ cookiecutter.project_slug }};
       };
+    };
 }

{{cookiecutter.project_slug}}/nix/{{cookiecutter.project_slug}}/build-systems-overlay.nix

@@ -0,0 +1,22 @@
+final: prev:
+let
+  inherit (final) resolveBuildSystem;
+  inherit (builtins) mapAttrs;
+
+  # Build system dependencies specified in the shape expected by resolveBuildSystem
+  # The empty lists below are lists of optional dependencies.
+  #
+  # A package `foo` with specification written as:
+  # `setuptools-scm[toml]` in pyproject.toml would be written as
+  # `foo.setuptools-scm = [ "toml" ]` in Nix
+  buildSystemOverrides = {
+    # add dependencies here, e.g.:
+    # pyperclip.setuptools = [ ];
+  };
+in
+mapAttrs (
+  name: spec:
+  prev.${name}.overrideAttrs (old: {
+    nativeBuildInputs = old.nativeBuildInputs ++ resolveBuildSystem spec;
+  })
+) buildSystemOverrides

{{cookiecutter.project_slug}}/nix/{{cookiecutter.project_slug}}/default.nix

@@ -0,0 +1,44 @@
+{
+  lib,
+  callPackage,
+
+  pyproject-nix,
+  pyproject-build-systems,
+  uv2nix,
+
+  python
+}:
+let
+  pyproject-util = callPackage pyproject-nix.build.util {};
+  pyproject-packages = callPackage pyproject-nix.build.packages {
+    inherit python;
+  };
+
+  # load a uv workspace from a workspace root
+  workspace = uv2nix.lib.workspace.loadWorkspace {
+    workspaceRoot = ../..;
+  };
+
+  # create overlay
+  lockFileOverlay = workspace.mkPyprojectOverlay {
+    # prefer "wheel" over "sdist" due to maintance overhead
+    # there is no bundled set of overlays for "sdist" in uv2nix, in contrast to poetry2nix
+    sourcePreference = "wheel";
+  };
+
+  buildSystemsOverlay = import ./build-systems-overlay.nix;
+
+  # construct package set
+  pythonSet = pyproject-packages.overrideScope (lib.composeManyExtensions [
+    # make build tools available by default as these are not necessarily specified in python lock files
+    pyproject-build-systems.overlays.default
+    # include all packages from the python lock file
+    lockFileOverlay
+    # add build system overrides to certain python packages
+    buildSystemsOverlay
+  ]);
+in pyproject-util.mkApplication {
+  # default dependancy group enables no optional dependencies and no dependency-groups
+  venv = pythonSet.mkVirtualEnv "{{ cookiecutter.project_slug }}-env" workspace.deps.default;
+  package = pythonSet.{{ cookiecutter.project_slug }};
+}