From 0b669f348301d5c02f29a91aa4ded2c9cb904974 Mon Sep 17 00:00:00 2001
From: SulfurNitride <SulfurNitride@users.noreply.github.com>
Date: Thu, 12 Mar 2026 10:16:58 -0500
Subject: Fix NixOS CI: use nix python for cmake, venv only for pybind11 pin

FindPython needs the real nix Python (with dev headers), not the venv
wrapper. Save NIX_PYTHON3 before venv overrides PATH. Tested locally.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
---
 .github/workflows/ci.yml |   3 +-
 .gitignore               |   4 ++
 nix/mobase-shell.nix     | 126 ++++++++++++++++++++++++-----------------------
 3 files changed, 71 insertions(+), 62 deletions(-)

diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index fd072f1..268a272 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -101,10 +101,11 @@ jobs:
             cmake --install /tmp/libloot/build
 
             # Configure full project (only mobase target will be built)
+            # Use NIX_PYTHON3 (real nix python) for cmake, not the venv wrapper
             PYBIND11_DIR=\$(python3 -c 'import pybind11; print(pybind11.get_cmake_dir())')
             cmake -S . -B build-nix -G Ninja \
               -DCMAKE_BUILD_TYPE=RelWithDebInfo \
-              -DPython_EXECUTABLE=\$(which python3) \
+              -DPython_EXECUTABLE=\"\${NIX_PYTHON3}\" \
               -Dpybind11_DIR=\"\${PYBIND11_DIR}\" \
               -DBUILD_PLUGIN_PYTHON=ON \
               -DCMAKE_PREFIX_PATH=/tmp/libloot-install \
diff --git a/.gitignore b/.gitignore
index 96bb944..2e2bc91 100644
--- a/.gitignore
+++ b/.gitignore
@@ -35,3 +35,7 @@ __pycache__/
 
 # Generated settings files
 fomod-plus-settings.ini
+
+# Nix
+.nix-venv/
+result
diff --git a/nix/mobase-shell.nix b/nix/mobase-shell.nix
index c39dd02..ae5ad91 100644
--- a/nix/mobase-shell.nix
+++ b/nix/mobase-shell.nix
@@ -1,61 +1,65 @@
-{ pkgs ? import <nixpkgs> {} }:
-
-let
-  python = pkgs.python313;
-  pythonWithPkgs = python.withPackages (ps: [
-    ps.sip
-    ps.pyqt6
-  ]);
-in
-pkgs.mkShell {
-  nativeBuildInputs = with pkgs; [
-    cmake
-    ninja
-    pkg-config
-    git
-    rustc
-    cargo
-  ];
-
-  buildInputs = with pkgs; [
-    # Qt 6
-    qt6.qtbase
-    qt6.wrapQtAppsHook
-    qt6.qtwebengine
-    qt6.qtwebsockets
-    qt6.qtsvg
-    qt6.qtwayland
-
-    # Python
-    pythonWithPkgs
-
-    # Libraries
-    boost
-    sqlite
-    tinyxml-2
-    fontconfig
-    spdlog
-    fuse3
-    libcap
-    lz4
-    zlib
-    zstd
-    bzip2
-    xz
-    openssl
-    curl
-    tomlplusplus
-    fmt
-  ];
-
-  shellHook = ''
-    # 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}:$CMAKE_PREFIX_PATH"
-  '';
-}
+{ pkgs ? import <nixpkgs> {} }:
+
+let
+  python = pkgs.python313;
+  pythonWithPkgs = python.withPackages (ps: [
+    ps.sip
+    ps.pyqt6
+  ]);
+in
+pkgs.mkShell {
+  nativeBuildInputs = with pkgs; [
+    cmake
+    ninja
+    pkg-config
+    git
+    rustc
+    cargo
+  ];
+
+  buildInputs = with pkgs; [
+    # Qt 6
+    qt6.qtbase
+    qt6.wrapQtAppsHook
+    qt6.qtwebengine
+    qt6.qtwebsockets
+    qt6.qtsvg
+    qt6.qtwayland
+
+    # Python (withPackages for runtime, base python313 for dev headers/libpython)
+    pythonWithPkgs
+    python313
+
+    # Libraries
+    boost
+    sqlite
+    tinyxml-2
+    fontconfig
+    spdlog
+    fuse3
+    libcap
+    lz4
+    zlib
+    zstd
+    bzip2
+    xz
+    openssl
+    curl
+    tomlplusplus
+    fmt
+  ];
+
+  shellHook = ''
+    # Save the real nix Python before venv overrides PATH (cmake needs this)
+    export NIX_PYTHON3="$(command -v python3)"
+
+    # 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"
+  '';
+}
-- 
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