Add pyproject-nix overlay (#54)

Previously, when RV nix derivations were using `poetry2nix`, overriding
a nix input in nix was also overriding the python code and resources
used in `poetry2nix`. This allowed for easy overrides of python and K
semantics changes by utilizing nix overrides.

With the migration to `uv` and `uv2nix`, this was behavior was removed
due to the respective code not documenting it's purpose. In addition,
due to `uv2nix` relying on state-of-the-art python nix packaging tooling
`pyproject-nix` instead of `nixpkgs`, ensuring identical override
behaviour requires more nix logic.

This PR re-introduces this kind of behaviour with `uv2nix`, though it
depends on newly introduced overlays in the k nix flake.

### Example
You can override k by running: `nix build
github:runtimeverification/imp-semantics --override-input k-framework
~/path/to/local-k-checkout`. This will now also build kimp with the
python and K code in `~/path/to/local-k-checkout`.

Author: juliankuners

flake.nix

@@ -52,16 +52,22 @@
       };
       kimpOverlay = final: prev:
       let
+        kimp-pyk-pyproject = final.callPackage ./nix/kimp-pyk-pyproject {
+          inherit uv2nix;
+        };
         kimp-pyk = final.callPackage ./nix/kimp-pyk {
-          inherit pyproject-nix pyproject-build-systems uv2nix;
+          inherit pyproject-nix pyproject-build-systems kimp-pyk-pyproject;
+          pyproject-overlays = [
+            (k-framework.overlays.pyk-pyproject system)
+          ];
           python = final."python${pythonVer}";
         };
         kimp = final.callPackage ./nix/kimp {
           inherit kimp-pyk;
           rev = self.rev or null;
         };
       in {
-        inherit kimp;
+        inherit kimp kimp-pyk kimp-pyk-pyproject;
       };
       pkgs = import nixpkgs {
         inherit system;
@@ -90,12 +96,19 @@
         '';
       };
       packages = rec {
-        inherit (pkgs) kimp uv;
+        inherit (pkgs) kimp uv kimp-pyk kimp-pyk-pyproject;
         default = kimp;
       };
     }) // {
-      overlays.default = final: prev: {
-        inherit (self.packages.${final.system}) kimp;
+      overlays = {
+        default = final: prev: {
+          inherit (self.packages.${final.system}) kimp;
+        };
+        # this pyproject-nix overlay allows for overriding the python packages that are otherwise locked in `uv.lock`
+        # by using this overlay in dependant nix flakes, you ensure that nix overrides also override the python package     
+        pyk-pyproject = system: final: prev: {
+          inherit (self.packages.${system}.kimp-pyk-pyproject.lockFileOverlay final prev) kimp-pyk;
+        };
       };
     };
 }

nix/kimp-pyk-pyproject/default.nix

@@ -0,0 +1,23 @@
+{
+  lib,
+  callPackage,
+
+  uv2nix,
+}:
+let
+  src = callPackage ../kimp-source { };
+
+  # load a uv workspace from a workspace root
+  workspace = uv2nix.lib.workspace.loadWorkspace {
+    workspaceRoot = "${src}";
+  };
+
+  # 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";
+  };
+in {
+  inherit lockFileOverlay workspace;
+}

nix/kimp-pyk/default.nix

@@ -4,39 +4,30 @@
 
   pyproject-nix,
   pyproject-build-systems,
-  uv2nix,
+  kimp-pyk-pyproject,
+  pyproject-overlays,
 
   python
 }:
 let
+  inherit (kimp-pyk-pyproject) lockFileOverlay workspace;
+
   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 = callPackage ../kimp-source { };
-  };
-
-  # 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 [
+  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
-  ]);
+  ] ++ pyproject-overlays));
 in pyproject-util.mkApplication {
   # default dependancy group enables no optional dependencies and no dependency-groups
   venv = pythonSet.mkVirtualEnv "kimp-env" workspace.deps.default;