ENH: improve parsing of the $ARCHFLAGS environment variable

This allows to correctly handle repeated -arch flags.

Author: dnicolodi

mesonpy/__init__.py

@@ -646,9 +646,17 @@ def __init__(
         if sysconfig.get_platform().startswith('macosx-'):
             archflags = os.environ.get('ARCHFLAGS', '').strip()
             if archflags:
-                arch, *other = filter(None, (x.strip() for x in archflags.split('-arch')))
+
+                # parse the ARCHFLAGS environment variable
+                parser = argparse.ArgumentParser(add_help=False, allow_abbrev=False)
+                parser.add_argument('-arch', action='append')
+                args, unknown = parser.parse_known_args(archflags.split())
+                if unknown:
+                    raise ConfigError(f'Unknown flag specified in $ARCHFLAGS={archflags!r}')
+                arch, *other = set(args.arch)
                 if other:
                     raise ConfigError(f'Multi-architecture builds are not supported but $ARCHFLAGS={archflags!r}')
+
                 macver, _, nativearch = platform.mac_ver()
                 if arch != nativearch:
                     x = os.environ.setdefault('_PYTHON_HOST_PLATFORM', f'macosx-{macver}-{arch}')

tests/test_project.py

@@ -211,3 +211,36 @@ def test_compiler(venv, package_detect_compiler, tmp_path):
     venv.pip('install', os.fspath(tmp_path / wheel))
     compiler = venv.python('-c', 'import detect_compiler; print(detect_compiler.compiler())').strip()
     assert compiler == 'msvc'
+
+
+@pytest.mark.skipif(sys.platform != 'darwin', reason='macOS specific test')
+@pytest.mark.parametrize('archflags', [
+    '-arch x86_64',
+    '-arch arm64',
+    '-arch arm64 -arch arm64',
+])
+def test_archflags_envvar_parsing(package_purelib_and_platlib, monkeypatch, archflags):
+    try:
+        monkeypatch.setenv('ARCHFLAGS', archflags)
+        arch = archflags.split()[-1]
+        with mesonpy._project():
+            assert mesonpy._tags.Tag().platform.endswith(arch)
+    finally:
+        # revert environment variable setting done by the in-process build
+        os.environ.pop('_PYTHON_HOST_PLATFORM', None)
+
+
+@pytest.mark.skipif(sys.platform != 'darwin', reason='macOS specific test')
+@pytest.mark.parametrize('archflags', [
+    '-arch arm64 -arch x86_64',
+    '-arch arm64 -DFOO=1',
+])
+def test_archflags_envvar_parsing_invalid(package_purelib_and_platlib, monkeypatch, archflags):
+    try:
+        monkeypatch.setenv('ARCHFLAGS', archflags)
+        with pytest.raises(mesonpy.ConfigError):
+            with mesonpy._project():
+                pass
+    finally:
+        # revert environment variable setting done by the in-process build
+        os.environ.pop('_PYTHON_HOST_PLATFORM', None)