BUG: ignore empty directories when checking package splits

mesonpy/__init__.py

@@ -146,7 +146,6 @@ def _map_to_wheel(sources: Dict[str, Dict[str, Any]],
                   exclude: List[str], include: List[str]) -> DefaultDict[str, List[_Entry]]:
     """Map files to the wheel, organized by wheel installation directory."""
     wheel_files: DefaultDict[str, List[_Entry]] = collections.defaultdict(list)
-    packages: Dict[str, str] = {}
     excluded = _compile_patterns(exclude)
     included = _compile_patterns(include)
 
@@ -165,18 +164,6 @@ def _map_to_wheel(sources: Dict[str, Dict[str, Any]],
             if path is None:
                 raise BuildError(f'Could not map installation path to an equivalent wheel directory: {str(destination)!r}')
 
-            if path == 'purelib' or path == 'platlib':
-                package = destination.parts[1]
-                other = packages.setdefault(package, path)
-                if other != path:
-                    this = os.fspath(pathlib.Path(path, *destination.parts[1:]))
-                    module = next(entry.dst for entry in wheel_files[other] if entry.dst.parts[0] == destination.parts[1])
-                    that = os.fspath(other / module)
-                    raise BuildError(
-                        f'The {package} package is split between {path} and {other}: '
-                        f'{this!r} and {that!r}, a "pure: false" argument may be missing in meson.build. '
-                        f'It is recommended to set it in "import(\'python\').find_installation()"')
-
             if key == 'install_subdirs' or key == 'targets' and os.path.isdir(src):
                 exclude_files = {os.path.normpath(x) for x in target.get('exclude_files', [])}
                 exclude_dirs = {os.path.normpath(x) for x in target.get('exclude_dirs', [])}
@@ -208,6 +195,17 @@ def _map_to_wheel(sources: Dict[str, Dict[str, Any]],
 
                 wheel_files[path].append(_Entry(dst, src, install_rpath, build_rpath))
 
+    purelib = {entry.dst.parts[0]: entry.dst for entry in wheel_files.get('purelib', [])}
+    for entry in wheel_files.get('platlib', []):
+        package = entry.dst.parts[0]
+        if package in purelib:
+            this = os.fspath('platlib' / entry.dst)
+            that = os.fspath('purelib' / purelib[package])
+            raise BuildError(
+                f'The {package} package is split between platlib and purelib: '
+                f'{this!r} and {that!r}, a "pure: false" argument may be missing in meson.build. '
+                f'It is recommended to set it in "import(\'python\').find_installation()"')
+
     return wheel_files
 
 

tests/packages/purelib-platlib-split/meson.build

@@ -6,13 +6,16 @@ project('purelib-platlib-split', version: '1.0.0')
 
 py = import('python').find_installation()
 
-py.install_sources(
-    'pure.py',
-    subdir: 'purelib-platlib-split',
+install_subdir(
+    'pure',
+    strip_directory: true,
+    exclude_files: get_option('empty') ? ['pure.py'] : [],
+    install_dir: py.get_install_dir() / 'purelib-platlib-split',
 )
 
-py.install_sources(
-    'plat.py',
-    subdir: 'purelib-platlib-split',
-    pure: false,
+# Use install_subdir() so this entry follows purelib in the install plan.
+install_subdir(
+    'plat',
+    strip_directory: true,
+    install_dir: py.get_install_dir(pure: false) / 'purelib-platlib-split',
 )

tests/packages/purelib-platlib-split/meson_options.txt

@@ -0,0 +1,5 @@
+# SPDX-FileCopyrightText: 2026 The meson-python developers
+#
+# SPDX-License-Identifier: MIT
+
+option('empty', type: 'boolean', value: false)

tests/test_wheel.py

@@ -371,6 +371,18 @@ def test_purelib_platlib_split(package_purelib_platlib_split, tmp_path):
             project.wheel(tmp_path)
 
 
+@pytest.mark.skipif(MESON_VERSION < (1, 1, 0), reason='meson too old to report excluded files')
+def test_purelib_platlib_empty_subdir(package_purelib_platlib_split, tmp_path):
+    filename = mesonpy.build_wheel(tmp_path, {'setup-args': ['-Dempty=true']})
+    artifact = wheel.wheelfile.WheelFile(tmp_path / filename)
+    assert wheel_contents(artifact) == {
+        'purelib_platlib_split-1.0.0.dist-info/METADATA',
+        'purelib_platlib_split-1.0.0.dist-info/RECORD',
+        'purelib_platlib_split-1.0.0.dist-info/WHEEL',
+        'purelib-platlib-split/plat.py',
+    }
+
+
 @pytest.mark.skipif(sys.platform != 'darwin', reason='macOS specific test')
 @pytest.mark.parametrize('arch', ['x86_64', 'arm64'])
 def test_archflags_envvar(package_purelib_and_platlib, monkeypatch, tmp_path, arch):