Fix NixOS CI: use venv for pinned pybind11 (nix Python is immutable)

Nix Python environments can't be modified with pip directly. Create a
temporary venv with --system-site-packages and install pybind11==2.13.6
into it.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

1 files changed, 16 insertions, 7 deletions

diff --git a/nix/mobase-shell.nix b/nix/mobase-shell.nix
index c6b326e..c39dd02 100644
--- a/nix/mobase-shell.nix
+++ b/nix/mobase-shell.nix
@@ -1,5 +1,12 @@
 { pkgs ? import <nixpkgs> {} }:

 

+let

+  python = pkgs.python313;

+  pythonWithPkgs = python.withPackages (ps: [

+    ps.sip

+    ps.pyqt6

+  ]);

+in

 pkgs.mkShell {

   nativeBuildInputs = with pkgs; [

     cmake

@@ -19,11 +26,8 @@ pkgs.mkShell {
     qt6.qtsvg

     qt6.qtwayland

 

-    # Python (pybind11 installed via pip in shellHook to pin version)

-    python313

-    python313Packages.pip

-    python313Packages.sip

-    python313Packages.pyqt6

+    # Python

+    pythonWithPkgs

 

     # Libraries

     boost

@@ -45,8 +49,13 @@ pkgs.mkShell {
   ];

 

   shellHook = ''

-    # Pin pybind11 to 2.13.6 (must match Docker build for ABI compat)

-    pip install --quiet pybind11==2.13.6 2>/dev/null || true

+    # Create a temporary venv to install pinned pybind11 (nixpkgs version is too new)

+    if [ ! -d .nix-venv ]; then

+      python3 -m venv .nix-venv --system-site-packages

+      .nix-venv/bin/pip install --quiet pybind11==2.13.6

+    fi

+    export PATH="$PWD/.nix-venv/bin:$PATH"

+    export PYTHONPATH="$PWD/.nix-venv/lib/python3.13/site-packages:$PYTHONPATH"

     export CMAKE_PREFIX_PATH="${pkgs.qt6.qtbase}:${pkgs.qt6.qtwebengine}:${pkgs.qt6.qtwebsockets}:${pkgs.qt6.qtsvg}:$CMAKE_PREFIX_PATH"

   '';

 }