migrate to uv2nix

Signed-off-by: ahuston-0 <aliceghuston@gmail.com>

uv-shell.nix

@@ -0,0 +1,125 @@
+{
+  lib,
+  pkgs,
+  python,
+  workspace,
+  pythonSet,
+  ...
+}:
+
+{
+  # It is of course perfectly OK to keep using an impure virtualenv workflow and only use uv2nix to build packages.
+  # This devShell simply adds Python and undoes the dependency leakage done by Nixpkgs Python infrastructure.
+  impure = pkgs.mkShell {
+    packages = [
+      python
+      pkgs.uv
+    ];
+    env =
+      {
+        # Prevent uv from managing Python downloads
+        UV_PYTHON_DOWNLOADS = "never";
+        # Force uv to use nixpkgs Python interpreter
+        UV_PYTHON = python.interpreter;
+      }
+      // lib.optionalAttrs pkgs.stdenv.isLinux {
+        # Python libraries often load native shared objects using dlopen(3).
+        # Setting LD_LIBRARY_PATH makes the dynamic library loader aware of libraries without using RPATH for lookup.
+        LD_LIBRARY_PATH = lib.makeLibraryPath pkgs.pythonManylinuxPackages.manylinux1;
+      };
+    shellHook = ''
+      unset PYTHONPATH
+    '';
+  };
+
+  # This devShell uses uv2nix to construct a virtual environment purely from Nix, using the same dependency specification as the application.
+  # The notable difference is that we also apply another overlay here enabling editable mode ( https://setuptools.pypa.io/en/latest/userguide/development_mode.html ).
+  #
+  # This means that any changes done to your local files do not require a rebuild.
+  #
+  # Note: Editable package support is still unstable and subject to change.
+  uv2nix =
+    let
+      # Create an overlay enabling editable mode for all local dependencies.
+      editableOverlay = workspace.mkEditablePyprojectOverlay {
+        # Use environment variable
+        root = "$REPO_ROOT";
+        # Optional: Only enable editable for these packages
+        # members = [ "flupdt" ];
+      };
+
+      # Override previous set with our overrideable overlay.
+      editablePythonSet = pythonSet.overrideScope (
+        lib.composeManyExtensions [
+          editableOverlay
+
+          # Apply fixups for building an editable package of your workspace packages
+          (final: prev: {
+            flupdt = prev.flupdt.overrideAttrs (old: {
+              # It's a good idea to filter the sources going into an editable build
+              # so the editable package doesn't have to be rebuilt on every change.
+              src = lib.fileset.toSource {
+                root = old.src;
+                fileset = lib.fileset.unions [
+                  (old.src + "/pyproject.toml")
+                  (old.src + "/README.md")
+                  (old.src + "/flupdt/__init__.py")
+                  (old.src + "/flupdt/cli.py")
+                  (old.src + "/flupdt/common.py")
+                  (old.src + "/flupdt/flake_build.py")
+                  (old.src + "/flupdt/flake_diff.py")
+                  (old.src + "/flupdt/flake_eval.py")
+                  (old.src + "/flupdt/flake_show.py")
+                  (old.src + "/flupdt/main.py")
+                ];
+              };
+
+              # Hatchling (our build system) has a dependency on the `editables` package when building editables.
+              #
+              # In normal Python flows this dependency is dynamically handled, and doesn't need to be explicitly declared.
+              # This behaviour is documented in PEP-660.
+              #
+              # With Nix the dependency needs to be explicitly declared.
+              nativeBuildInputs =
+                old.nativeBuildInputs
+                ++ final.resolveBuildSystem {
+                  editables = [ ];
+                };
+            });
+
+          })
+        ]
+      );
+
+      # Build virtual environment, with local packages being editable.
+      #
+      # Enable all optional dependencies for development.
+      virtualenv = editablePythonSet.mkVirtualEnv "flupdt-dev-env" workspace.deps.all;
+
+    in
+    pkgs.mkShell {
+      packages = [
+        virtualenv
+        pkgs.uv
+      ];
+
+      env = {
+        # Don't create venv using uv
+        UV_NO_SYNC = "1";
+
+        # Force uv to use Python interpreter from venv
+        UV_PYTHON = "${virtualenv}/bin/python";
+
+        # Prevent uv from downloading managed Python's
+        UV_PYTHON_DOWNLOADS = "never";
+      };
+
+      shellHook = ''
+        # Undo dependency propagation by nixpkgs.
+        unset PYTHONPATH
+
+        # Get repository root using git. This is expanded at runtime by the editable `.pth` machinery.
+        export REPO_ROOT=$(git rev-parse --show-toplevel)
+      '';
+    };
+}