Add Windows arm tests

.github/workflows/ci.yml

@@ -1205,3 +1205,134 @@ jobs:
 
       - name: Clean directory
         run: git clean -fdx
+
+  # Clang with MSVC/Windows SDK toolchain + python.org CPython (Windows ARM)
+  windows_arm_clang_msvc:
+    if: github.event.pull_request.draft == false
+
+    strategy:
+      fail-fast: false
+      matrix:
+        os: [windows-11-arm]
+        python: ['3.13']
+
+    runs-on: "${{ matrix.os }}"
+    timeout-minutes: 90
+
+    name: "🐍 ${{ matrix.python }} • ${{ matrix.os }} • clang-msvc"
+
+    steps:
+      - name: Show env
+        run: env
+
+      - name: Checkout
+        uses: actions/checkout@v6
+
+      - name: Setup Python ${{ matrix.python }}
+        uses: actions/setup-python@v6
+        with:
+          python-version: ${{ matrix.python }}
+          architecture: arm64
+
+      - name: Run pip installs
+        run: |
+          python -m pip install --upgrade pip
+          python -m pip install -r tests/requirements.txt
+
+      - name: Configure CMake
+        run: >
+          cmake -G Ninja -S . -B .
+          -DPYBIND11_WERROR=OFF
+          -DPYBIND11_SIMPLE_GIL_MANAGEMENT=OFF
+          -DDOWNLOAD_CATCH=ON
+          -DDOWNLOAD_EIGEN=ON
+          -DCMAKE_CXX_COMPILER=clang++
+          -DCMAKE_CXX_STANDARD=20
+          -DPython_ROOT_DIR="$env:Python_ROOT_DIR"
+
+      - name: Build
+        run: cmake --build . -j 2
+
+      - name: Python tests
+        run: cmake --build . --target pytest -j 2
+
+      - name: C++ tests
+        run: cmake --build . --target cpptest -j 2
+
+      - name: Interface test
+        run: cmake --build . --target test_cmake_build -j 2
+
+      - name: Visibility test
+        run: cmake --build . --target test_cross_module_rtti -j 2
+
+  # Clang in MSYS2/MinGW-w64 CLANGARM64 toolchain + MSYS2 Python (Windows ARM)
+  windows_arm_clang_msys2:
+    if: github.event.pull_request.draft == false
+
+    strategy:
+      fail-fast: false
+      matrix:
+        os: [windows-11-arm]
+
+    runs-on: "${{ matrix.os }}"
+    timeout-minutes: 90
+
+    name: "${{ matrix.os }} • clang-msys2"
+
+    defaults:
+      run:
+        shell: msys2 {0}
+
+    steps:
+    - uses: actions/checkout@v6
+      with:
+        submodules: true
+
+    - uses: msys2/setup-msys2@v2
+      with:
+        msystem: CLANGARM64
+        update: true
+        install: |
+          mingw-w64-clang-aarch64-cmake
+          mingw-w64-clang-aarch64-clang
+          mingw-w64-clang-aarch64-ninja
+          mingw-w64-clang-aarch64-python-pip
+          mingw-w64-clang-aarch64-python-pytest
+          mingw-w64-clang-aarch64-python-numpy
+
+    - name: Debug info
+      run: |
+        clang++ --version
+        cmake --version
+        ninja --version
+        python --version
+
+    - name: Run pip installs
+      run: |
+        python -m pip install --upgrade pip
+        python -m pip install -r tests/requirements.txt
+
+    - name: Configure CMake
+      run: >-
+        cmake -S . -B build
+        -DPYBIND11_WERROR=OFF
+        -DDOWNLOAD_CATCH=ON
+        -DDOWNLOAD_EIGEN=ON
+        -DCMAKE_CXX_COMPILER=clang++
+        -DCMAKE_CXX_STANDARD=20
+        -DPYTHON_EXECUTABLE=$(python -c "import sys; print(sys.executable)")
+
+    - name: Build
+      run: cmake --build build -j 2
+
+    - name: Python tests
+      run: cmake --build build --target pytest -j 2
+
+    - name: C++ tests
+      run: PYTHONHOME=/clangarm64 PYTHONPATH=/clangarm64 cmake --build build --target cpptest -j 2
+
+    - name: Interface test
+      run: cmake --build build --target test_cmake_build -j 2
+
+    - name: Visibility test
+      run: cmake --build build --target test_cross_module_rtti -j 2

tests/requirements.txt

@@ -7,8 +7,9 @@ numpy~=2.2.0; python_version=="3.10" and platform_python_implementation=="PyPy"
 numpy~=1.26.0; platform_python_implementation=="GraalVM" and sys_platform=="linux"
 numpy~=1.21.5; platform_python_implementation=="CPython" and python_version>="3.8" and python_version<"3.10"
 numpy~=1.22.2; platform_python_implementation=="CPython" and python_version=="3.10"
-numpy~=1.26.0; platform_python_implementation=="CPython" and python_version>="3.11" and python_version<"3.13"
-numpy~=2.2.0; platform_python_implementation=="CPython" and python_version=="3.13"
+numpy~=1.26.0; platform_python_implementation=="CPython" and python_version>="3.11" and python_version<"3.13" and platform_machine!="ARM64"
+numpy~=2.3.0; platform_python_implementation=="CPython" and python_version>="3.11" and platform_machine=="ARM64"
+numpy~=2.2.0; platform_python_implementation=="CPython" and python_version=="3.13" and platform_machine!="ARM64"
 pytest>=6
 pytest-timeout
 scipy~=1.5.4; platform_python_implementation=="CPython" and python_version<"3.10"

tests/test_unnamed_namespace_a.py

@@ -5,7 +5,10 @@
 from pybind11_tests import unnamed_namespace_a as m
 from pybind11_tests import unnamed_namespace_b as mb
 
-XFAIL_CONDITION = "not m.defined_WIN32_or__WIN32 and (m.defined___clang__ or m.defined__LIBCPP_VERSION)"
+XFAIL_CONDITION = (
+    "m.defined__LIBCPP_VERSION or "
+    "(not m.defined_WIN32_or__WIN32 and m.defined___clang__)"
+)
 XFAIL_REASON = "Known issues: https://github.com/pybind/pybind11/pull/4319"