TST: verify that compilation uses MSVC when available

tests/packages/detect-compiler/detect_compiler.c

@@ -0,0 +1,38 @@
+// SPDX-FileCopyrightText: 2023 The meson-python developers
+//
+// SPDX-License-Identifier: MIT
+
+#include <Python.h>
+
+#if defined _MSC_VER
+#  define _COMPILER "msvc"
+#elif defined __clang__
+#  define _COMPILER "clang"
+#elif defined __GNUC__
+#  define _COMPILER "gcc"
+#else
+#  define _COMPILER "unknown"
+#endif
+
+static PyObject* compiler(PyObject* self)
+{
+    return PyUnicode_FromString(_COMPILER);
+}
+
+static PyMethodDef methods[] = {
+    {"compiler", (PyCFunction)compiler, METH_NOARGS, NULL},
+    {NULL, NULL, 0, NULL},
+};
+
+static struct PyModuleDef module = {
+    PyModuleDef_HEAD_INIT,
+    "detect_compiler",
+    NULL,
+    -1,
+    methods,
+};
+
+PyMODINIT_FUNC PyInit_detect_compiler(void)
+{
+    return PyModule_Create(&module);
+}

tests/packages/detect-compiler/meson.build

@@ -0,0 +1,13 @@
+# SPDX-FileCopyrightText: 2023 The meson-python developers
+#
+# SPDX-License-Identifier: MIT
+
+project(
+    'detect-compiler',
+    'c',
+    version: '1.0',
+)
+
+py = import('python').find_installation()
+
+py.extension_module('detect_compiler', 'detect_compiler.c', install: true)

tests/packages/detect-compiler/pyproject.toml

@@ -0,0 +1,7 @@
+# SPDX-FileCopyrightText: 2023 The meson-python developers
+#
+# SPDX-License-Identifier: MIT
+
+[build-system]
+build-backend = 'mesonpy'
+requires = ['meson-python']

tests/test_project.py

@@ -3,7 +3,7 @@
 # SPDX-License-Identifier: MIT
 
 import ast
-import os.path
+import os
 import platform
 import shutil
 import sys
@@ -219,3 +219,15 @@ def test_invalid_build_dir(package_pure, tmp_path, mocker):
     assert meson.call_args_list[0].args[1][1] == 'setup'
     assert '--reconfigure' not in meson.call_args_list[0].args[1]
     project.build()
+
+
+@pytest.mark.skipif(not os.getenv('CI') or platform.system() != 'Windows', reason='Requires MSVC')
+def test_compiler(venv, package_detect_compiler, tmp_path):
+    # Check that things are setup properly to use the MSVC compiler on
+    # Windows. This effectively means running the compilation step
+    # with 'meson compile' instead of 'ninja' on Windows. Run this
+    # test only on CI where we know that MSVC is available.
+    wheel = mesonpy.build_wheel(tmp_path, {'setup-args': ['--vsenv']})
+    venv.pip('install', os.fspath(tmp_path / wheel))
+    compiler = venv.python('-c', 'import detect_compiler; print(detect_compiler.compiler())').strip()
+    assert compiler == 'msvc'