Run tests on macOS and Windows and fix the Windows failures

.github/workflows/build.yaml

@@ -28,9 +28,15 @@ jobs:
     runs-on: ${{ matrix.os }}
 
     strategy:
+      fail-fast: false
       matrix:
         os: [ubuntu-24.04]
         python-version: ["3.11", "3.12", "3.13"]
+        include:
+          - os: macos-26
+            python-version: "3.11"
+          - os: windows-2025
+            python-version: "3.11"
 
     steps:
       - name: Checkout
@@ -43,14 +49,22 @@ jobs:
         with:
           version: ${{ matrix.python-version }}
 
+      - name: Setup C++
+        uses: actions-ext/cpp/setup@7de57593fbcba72d513072bfb4b30b5a344aa547
+        with:
+          cache: 'false'
+          clang_format: 'false'
+
       - name: Install dependencies
         run: make develop
 
       - name: Lint
         run: make lint
+        if: runner.os == 'Linux'
 
       - name: Checks
         run: make checks
+        if: runner.os == 'Linux'
 
       - name: Build
         run: make build
@@ -69,6 +83,7 @@ jobs:
         uses: EnricoMi/publish-unit-test-result-action@7622c5bf3d112a72ab4fa3951c2aa5723d8ab92d  # v2.25.0
         with:
           files: '**/junit.xml'
+        if: runner.os == 'Linux'
 
       - name: Upload coverage
         uses: codecov/codecov-action@303a32d7a59b442fa8d48b6a1cc6825c09c847a5  # v7.1.1

hatch_cpp/config.py

@@ -197,8 +197,8 @@ def generate(self):
                 if self.platform.platform == "emscripten":
                     objects = []
                     for source_index, source in enumerate(library.sources):
-                        obj = Path("build/hatch-cpp") / f"{library_index}-{source_index}-{Path(source).stem}.o"
-                        objects.append(str(obj))
+                        obj = f"build/hatch-cpp/{library_index}-{source_index}-{Path(source).stem}.o"
+                        objects.append(obj)
                         self.commands.append(f"{compiler} -c {source} {compile_flags} -o {obj}")
                     self.commands.append(f"{compiler} {' '.join(objects)} {link_flags}")
                 else:

hatch_cpp/tests/test_projects.py

@@ -15,7 +15,12 @@ class TestProject:
         [
             "test_project_basic",
             "test_project_override_classes",
-            "test_project_override_toolchain",
+            pytest.param(
+                "test_project_override_toolchain",
+                marks=pytest.mark.skipif(
+                    platform == "win32", reason="the fixture selects the gcc toolchain, whose flags clang rejects for MSVC targets"
+                ),
+            ),
             "test_project_pybind",
             "test_project_pybind_vcpkg",
             "test_project_nanobind",

hatch_cpp/tests/test_vcpkg_ref.py

@@ -125,6 +125,11 @@ def _make_vcpkg_env(self, tmp_path):
         """Create a minimal vcpkg.json so generate() produces commands."""
         (tmp_path / "vcpkg.json").write_text("{}")
 
+    def _pin_linux_host(self, monkeypatch):
+        """Make generate() behave as on an x86_64 Linux host, whatever host runs the test."""
+        monkeypatch.setattr("hatch_cpp.toolchains.vcpkg.sys_platform", "linux")
+        monkeypatch.setattr("hatch_cpp.toolchains.vcpkg.platform_machine", lambda: "x86_64")
+
     def test_generate_with_explicit_ref(self, tmp_path, monkeypatch):
         monkeypatch.chdir(tmp_path)
         self._make_vcpkg_env(tmp_path)
@@ -164,6 +169,7 @@ def test_generate_without_ref(self, tmp_path, monkeypatch):
 
     def test_generate_uses_posix_command_paths(self, tmp_path, monkeypatch):
         monkeypatch.chdir(tmp_path)
+        self._pin_linux_host(monkeypatch)
         self._make_vcpkg_env(tmp_path)
 
         cfg = HatchCppVcpkgConfiguration(vcpkg_triplet="x64-linux")
@@ -185,6 +191,7 @@ def test_generate_detects_linux_arm64_triplet(self, tmp_path, monkeypatch):
 
     def test_generate_detects_emscripten_triplet(self, tmp_path, monkeypatch):
         monkeypatch.chdir(tmp_path)
+        self._pin_linux_host(monkeypatch)
         self._make_vcpkg_env(tmp_path)
         build_plan = SimpleNamespace(platform=SimpleNamespace(platform="emscripten"))
 
@@ -206,6 +213,7 @@ def test_generate_uses_windows_command_paths(self, tmp_path, monkeypatch):
 
     def test_generate_skips_clone_when_vcpkg_root_exists(self, tmp_path, monkeypatch):
         monkeypatch.chdir(tmp_path)
+        self._pin_linux_host(monkeypatch)
         self._make_vcpkg_env(tmp_path)
         vcpkg_root = tmp_path / "vcpkg"
         vcpkg_root.mkdir()
@@ -225,6 +233,7 @@ def test_generate_skips_clone_when_vcpkg_root_exists(self, tmp_path, monkeypatch
 
     def test_generate_reclones_when_vcpkg_root_exists_but_empty(self, tmp_path, monkeypatch):
         monkeypatch.chdir(tmp_path)
+        self._pin_linux_host(monkeypatch)
         self._make_vcpkg_env(tmp_path)
         (tmp_path / "vcpkg").mkdir()
 
@@ -253,6 +262,7 @@ def test_generate_bootstraps_when_vcpkg_executable_missing(self, tmp_path, monke
 
     def test_generate_reclones_when_vcpkg_exists_but_not_working(self, tmp_path, monkeypatch):
         monkeypatch.chdir(tmp_path)
+        self._pin_linux_host(monkeypatch)
         self._make_vcpkg_env(tmp_path)
         vcpkg_root = tmp_path / "vcpkg"
         vcpkg_root.mkdir()

hatch_cpp/toolchains/cmake.py

@@ -54,13 +54,10 @@ def generate(self, config) -> list[str]:
             commands[-1] += f" -DCMAKE_INSTALL_PREFIX={Path(self.root).parent}"
 
         # TODO: CMAKE_CXX_COMPILER
-        # Respect CMAKE_GENERATOR environment variable
+        # Respect CMAKE_GENERATOR environment variable. Without it CMake picks its default,
+        # which on Windows is the newest installed Visual Studio.
         cmake_generator = environ.get("CMAKE_GENERATOR", "")
-        if config.platform.platform == "win32":
-            if not cmake_generator:
-                cmake_generator = "Visual Studio 17 2022"
-            commands[-1] += f' -G "{cmake_generator}"'
-        elif cmake_generator:
+        if cmake_generator:
             commands[-1] += f' -G "{cmake_generator}"'
 
         # Put in CMake flags

hatch_cpp/toolchains/vcpkg.py

@@ -57,7 +57,7 @@ def _read_vcpkg_ref_from_gitmodules(vcpkg_root: Path) -> str | None:
     parser.read(str(gitmodules_path))
 
     for section in parser.sections():
-        if parser.get(section, "path", fallback=None) == str(vcpkg_root):
+        if parser.get(section, "path", fallback=None) == vcpkg_root.as_posix():
             return parser.get(section, "branch", fallback=None)
 
     return None
@@ -93,7 +93,7 @@ def _vcpkg_executable_path(self) -> Path:
     def _command_path(self, path: Path) -> str:
         if sys_platform == "win32":
             return str(path).replace("/", "\\")
-        return f"./{path}"
+        return f"./{path.as_posix()}"
 
     def _delete_dir_command(self, path: Path) -> str:
         if sys_platform == "win32":