build.hooks.pyprojectHook: Revert to using pypa/installer for cross installs

Uv's internal interpreter discovery doesn't work for cross compiled environments and detects the wrong arch glibc.
We can work around this issue by using pypa/installer for cross compiled builds, but still use uv for native.

Author: adisbladis

build/checks/build-systems.nix

@@ -402,6 +402,30 @@ let
             };
         };
 
+      installer =
+        {
+          stdenv,
+          python3Packages,
+          pyprojectHook,
+          resolveBuildSystem,
+        }:
+        stdenv.mkDerivation {
+          inherit (python3Packages.installer)
+            pname
+            version
+            src
+            meta
+            ;
+
+          nativeBuildInputs =
+            [
+              pyprojectHook
+            ]
+            ++ resolveBuildSystem {
+              flit-core = [ ];
+            };
+        };
+
       setuptools =
         {
           stdenv,

build/hooks/default.nix

@@ -13,6 +13,8 @@ let
   inherit (pkgs) buildPackages;
   pythonSitePackages = python.sitePackages;
 
+  isCross = stdenv.buildPlatform != stdenv.hostPlatform;
+
   # When cross compiling create a virtual environment for the build.
   #
   # Because Nixpkgs builds cross compiled Python in a separate
@@ -29,7 +31,7 @@ let
   '';
 
   pythonInterpreter =
-    if stdenv.buildPlatform != stdenv.hostPlatform then
+    if isCross then
       "${crossPython}/bin/${baseNameOf pythonOnBuildForHost.interpreter}"
     else
       pythonOnBuildForHost.interpreter;
@@ -51,9 +53,7 @@ in
       substitutions = {
         inherit pythonInterpreter;
         pythonPath = lib.concatStringsSep ":" (
-          lib.optional (
-            stdenv.buildPlatform != stdenv.hostPlatform
-          ) "${python.pythonOnBuildForHost}/${python.sitePackages}"
+          lib.optional isCross "${python.pythonOnBuildForHost}/${python.sitePackages}"
           ++ [
             "${python}/${python.sitePackages}"
           ]
@@ -194,13 +194,18 @@ in
               pyprojectInstallHook
               pyprojectOutputSetupHook
             ]
-            ++ lib.optional (stdenv.buildPlatform != stdenv.hostPlatform) pyprojectCrossShebangHook
+            ++ lib.optional isCross pyprojectCrossShebangHook
             ++ extraHooks;
         } ./meta-hook.sh
       )
-      {
-        python = pythonOnBuildForHost;
-      };
+      (
+        {
+          python = pythonOnBuildForHost;
+        }
+        // lib.optionalAttrs isCross {
+          pyprojectInstallHook = hooks.pyprojectPypaInstallHook;
+        }
+      );
 
   /*
     Hook used to build prebuilt wheels.
@@ -250,4 +255,21 @@ in
       };
     } ./pyproject-fixup-editable-hook.sh
   ) { };
+
+  /*
+    Install hook using pypa/installer.
+
+    Used instead of `pyprojectInstallHook` for cross compilation support.
+  */
+  pyprojectPypaInstallHook = callPackage (
+    { pythonPkgsBuildHost }:
+    makeSetupHook {
+      name = "pyproject-pypa-install-hook";
+      substitutions = {
+        inherit (pythonPkgsBuildHost) installer;
+        inherit pythonInterpreter pythonSitePackages;
+        wrapper = ./pypa-install-hook/wrapper.py;
+      };
+    } ./pypa-install-hook/pyproject-pypa-install-hook.sh
+  ) { };
 }

build/hooks/pypa-install-hook/pyproject-pypa-install-hook.sh

@@ -0,0 +1,26 @@
+# Setup hook for Pyproject installer.
+echo "Sourcing pyproject-pypa-install-hook"
+
+pyprojectPypaInstallPhase() {
+  echo "Executing pyprojectPypaInstallPhase"
+  runHook preInstall
+
+  pushd dist >/dev/null
+
+  for wheel in *.whl; do
+    env PYTHONPATH=$PYTHONPATH:@installer@/@pythonSitePackages@ @pythonInterpreter@ @wrapper@ --prefix "$out" "$wheel"
+    echo "Successfully installed $wheel"
+  done
+
+  rm -f "$out/.lock"
+
+  popd >/dev/null
+
+  runHook postInstall
+  echo "Finished executing pyprojectPypaInstallPhase"
+}
+
+if [ -z "${dontUsePyprojectInstall-}" ] && [ -z "${installPhase-}" ]; then
+  echo "Using pyprojectPypaInstallPhase"
+  installPhase=pyprojectPypaInstallPhase
+fi

build/hooks/pypa-install-hook/wrapper.py

@@ -0,0 +1,22 @@
+#!/usr/bin/env python3
+import os
+import sys
+
+
+def main():
+    """
+    Provides compatibility with uv env vars when using pypa/installer.
+    Ideally uv should also be used for cross installs, but for now it's not compatible.
+    """
+    compile_bytecode = bool(os.environ.get("UV_COMPILE_BYTECODE", False))
+
+    args = sys.argv[1:]
+    if compile_bytecode:
+        args.insert(0, "1")
+        args.insert(0, "--compile-bytecode")
+
+    os.execv(sys.executable, [sys.executable, "-m", "installer", *args])
+
+
+if __name__ == "__main__":
+    main()