Add pyproject-nix overlay in nix derivation (#724)

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: `kup install kmir --override k-framework
~/path/to/local-k-checkout`. This will now also build kmir with the
python and K code in `~/path/to/local-k-checkout`.

---------

Co-authored-by: Jost Berthold <jost.berthold@gmail.com>
Co-authored-by: Tamás Tóth <tothtamas28@users.noreply.github.com>

Author: 3 people

flake.nix

@@ -73,15 +73,22 @@
           final: prev:
           let
             rev = self.rev or null;
+            kmir-pyk-pyproject = final.callPackage ./nix/kmir-pyk-pyproject { inherit uv2nix; };
             kmir-pyk = final.callPackage ./nix/kmir-pyk {
-              inherit pyproject-nix pyproject-build-systems uv2nix;
+              inherit pyproject-nix pyproject-build-systems kmir-pyk-pyproject;
               python = final."python${pythonVer}";
+              pyproject-overlays = [ (k-framework.overlays.pyk-pyproject system) ];
             };
             kmir = final.callPackage ./nix/kmir { inherit kmir-pyk rev; };
             kmir-package-test = final.callPackage ./nix/test/package.nix { inherit rev; };
           in
           {
-            inherit kmir-pyk kmir kmir-package-test;
+            inherit
+              kmir-pyk
+              kmir
+              kmir-package-test
+              kmir-pyk-pyproject
+              ;
           };
         pkgs = import nixpkgs {
           inherit system;
@@ -137,5 +144,12 @@
     )
     // {
       overlays.default = final: prev: { inherit (self.packages.${final.system}) kmir; };
+      pyprojectOverlays = {
+        # 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}.kmir-pyk-pyproject.lockFileOverlay final prev) kmir-pyk;
+        };
+      };
     };
 }

nix/kmir-pyk-pyproject/default.nix

@@ -0,0 +1,23 @@
+{
+  lib,
+  callPackage,
+  nix-gitignore,
+
+  uv2nix,
+}:
+let
+  src = callPackage ../kmir-source { };
+
+  # load a uv workspace from a workspace root
+  workspace = uv2nix.lib.workspace.loadWorkspace { workspaceRoot = "${src}/kmir"; };
+
+  # 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/kmir-pyk/default.nix

@@ -1,42 +1,35 @@
 {
   lib,
   callPackage,
-  nix-gitignore,
 
   pyproject-nix,
   pyproject-build-systems,
-  uv2nix,
+  kmir-pyk-pyproject,
+  pyproject-overlays ? [ ],
 
   python,
 }:
 let
+  inherit (kmir-pyk-pyproject) lockFileOverlay workspace;
+
   pyproject-util = callPackage pyproject-nix.build.util { };
   pyproject-packages = callPackage pyproject-nix.build.packages { inherit python; };
 
-  src = callPackage ../kmir-source { };
-
-  # load a uv workspace from a workspace root
-  workspace = uv2nix.lib.workspace.loadWorkspace { workspaceRoot = "${src}/kmir"; };
-
-  # 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
-    ]
+    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 {