ENH: add support for PEP 639

Author: dnicolodi

mesonpy/__init__.py

@@ -53,6 +53,20 @@
 from mesonpy._compat import cached_property, read_binary
 
 
+try:
+    from packaging.licenses import InvalidLicenseExpression, canonicalize_license_expression
+except ImportError:
+    # PEP-639 support requires packaging >= 24.2.
+    def canonicalize_license_expression(s: str) -> str:  # type: ignore[misc]
+        warnings.warn(
+            'canonicalization and validation of license expression in "project.license" '
+            'as defined by PEP-639 requires packaging version 24.2 or later.', stacklevel=2)
+        return s
+
+    class InvalidLicenseExpression(Exception):  # type: ignore[no-redef]
+        pass
+
+
 if typing.TYPE_CHECKING:  # pragma: no cover
     from typing import Any, Callable, DefaultDict, Dict, List, Literal, Optional, Sequence, TextIO, Tuple, Type, TypeVar, Union
 
@@ -251,6 +265,10 @@ def from_pyproject(  # type: ignore[override]
             fields = ', '.join(f'"{x}"' for x in unsupported_dynamic)
             raise pyproject_metadata.ConfigurationError(f'Unsupported dynamic fields: {fields}')
 
+        # Validate license field to be a valid SDPX license expression.
+        if isinstance(metadata.license, str):
+            metadata.license = canonicalize_license_expression(metadata.license)
+
         return metadata
 
     @property
@@ -339,13 +357,6 @@ def _data_dir(self) -> str:
     def _libs_dir(self) -> str:
         return f'.{self._metadata.distribution_name}.mesonpy.libs'
 
-    @property
-    def _license_file(self) -> Optional[pathlib.Path]:
-        license_ = self._metadata.license
-        if license_ and isinstance(license_, pyproject_metadata.License):
-            return license_.file
-        return None
-
     @property
     def wheel(self) -> bytes:
         """Return WHEEL file for dist-info."""
@@ -428,9 +439,17 @@ def _wheel_write_metadata(self, whl: mesonpy._wheelfile.WheelFile) -> None:
         if self.entrypoints_txt:
             whl.writestr(f'{self._distinfo_dir}/entry_points.txt', self.entrypoints_txt)
 
-        # add license (see https://github.com/mesonbuild/meson-python/issues/88)
-        if self._license_file:
-            whl.write(self._license_file, f'{self._distinfo_dir}/{os.path.basename(self._license_file)}')
+        # Add pre-PEP-639 license files.
+        if isinstance(self._metadata.license, pyproject_metadata.License):
+            license_file = self._metadata.license.file
+            if license_file:
+                whl.write(license_file, f'{self._distinfo_dir}/{os.path.basename(license_file)}')
+
+        # Add PEP-639 license-files. Use ``getattr()`` for compatibility with pyproject-metadata < 0.9.0.
+        license_files = getattr(self._metadata, 'license_files', None)
+        if license_files:
+            for f in license_files:
+                whl.write(f, f'{self._distinfo_dir}/licenses/{pathlib.Path(f).as_posix()}')
 
     def build(self, directory: Path) -> pathlib.Path:
         wheel_file = pathlib.Path(directory, f'{self.name}.whl')
@@ -1023,7 +1042,7 @@ def wrapper(*args: P.args, **kwargs: P.kwargs) -> T:
         warnings.showwarning = _showwarning
         try:
             return func(*args, **kwargs)
-        except (Error, pyproject_metadata.ConfigurationError) as exc:
+        except (Error, InvalidLicenseExpression, pyproject_metadata.ConfigurationError) as exc:
             prefix = f'{style.ERROR}meson-python: error:{style.RESET} '
             _log('\n' + textwrap.indent(str(exc), prefix))
             raise SystemExit(1) from exc

tests/conftest.py

@@ -27,6 +27,17 @@
 
 def metadata(data):
     meta, other = packaging.metadata.parse_email(data)
+    # PEP-639 support requires packaging >= 24.1.  Add minimal
+    # handling of PEP-639 fields here to allow testing with older
+    # packaging releases.
+    value = other.pop('license-expression', None)
+    if value is not None:
+        # The ``License-Expression`` header should appear only once.
+        assert len(value) == 1
+        meta['license-expression'] = value[0]
+    value = other.pop('license-file', None)
+    if value is not None:
+        meta['license-file'] = value
     assert not other
     return meta
 

tests/packages/license-pep639/LICENSES/BSD-3-Clause.txt

@@ -0,0 +1 @@
+Placeholder, just for testing.

tests/packages/license-pep639/LICENSES/MIT.txt

@@ -0,0 +1 @@
+Placeholder, just for testing.

tests/packages/license-pep639/meson.build

@@ -0,0 +1,5 @@
+# SPDX-FileCopyrightText: 2022 The meson-python developers
+#
+# SPDX-License-Identifier: MIT
+
+project('license-pep639', version: '1.0.0')

tests/packages/license-pep639/pyproject.toml

@@ -0,0 +1,13 @@
+# SPDX-FileCopyrightText: 2022 The meson-python developers
+#
+# SPDX-License-Identifier: MIT
+
+[build-system]
+build-backend = 'mesonpy'
+requires = ['meson-python']
+
+[project]
+name = 'license-pep639'
+version = '1.0.0'
+license = 'MIT OR BSD-3-Clause'
+license-files = ['LICENSES/*']

tests/test_metadata.py

@@ -12,6 +12,12 @@
 from mesonpy import Metadata
 
 
+try:
+    import packaging.licenses as packaging_licenses
+except ImportError:
+    packaging_licenses = None
+
+
 def test_package_name():
     name = 'package.Test'
     metadata = Metadata(name='package.Test', version=packaging.version.Version('0.0.1'))
@@ -57,3 +63,25 @@ def test_missing_version(package_missing_version):
     ))
     with pytest.raises(pyproject_metadata.ConfigurationError, match=match):
         Metadata.from_pyproject(pyproject, pathlib.Path())
+
+
+@pytest.mark.skipif(packaging_licenses is None, reason='packaging too old')
+def test_normalize_license():
+    pyproject = {'project': {
+        'name': 'test',
+        'version': '1.2.3',
+        'license': 'mit or bsd-3-clause',
+    }}
+    metadata = Metadata.from_pyproject(pyproject, pathlib.Path())
+    assert metadata.license == 'MIT OR BSD-3-Clause'
+
+
+@pytest.mark.skipif(packaging_licenses is None, reason='packaging too old')
+def test_invalid_license():
+    pyproject = {'project': {
+        'name': 'test',
+        'version': '1.2.3',
+        'license': 'Foo',
+    }}
+    with pytest.raises(packaging_licenses.InvalidLicenseExpression, match='Unknown license: \'foo\''):
+        Metadata.from_pyproject(pyproject, pathlib.Path())

tests/test_wheel.py

@@ -12,14 +12,17 @@
 import textwrap
 
 import packaging.tags
+import pyproject_metadata
 import pytest
 import wheel.wheelfile
 
 import mesonpy
 
-from .conftest import adjust_packaging_platform_tag
+from .conftest import adjust_packaging_platform_tag, metadata
 
 
+PYPROJECT_METADATA_VERSION = tuple(map(int, pyproject_metadata.__version__.split('.')[:2]))
+
 _meson_ver_str = subprocess.run(['meson', '--version'], check=True, stdout=subprocess.PIPE, text=True).stdout
 MESON_VERSION = tuple(map(int, _meson_ver_str.split('.')[:3]))
 
@@ -140,6 +143,29 @@ def test_contents_license_file(wheel_license_file):
     assert artifact.read('license_file-1.0.0.dist-info/LICENSE.custom').rstrip() == b'Hello!'
 
 
+@pytest.mark.xfail(PYPROJECT_METADATA_VERSION < (0, 9), reason='pyproject-metadata too old')
+@pytest.mark.filterwarnings('ignore:canonicalization and validation of license expression')
+def test_license_pep639(wheel_license_pep639):
+    artifact = wheel.wheelfile.WheelFile(wheel_license_pep639)
+
+    assert wheel_contents(artifact) == {
+        'license_pep639-1.0.0.dist-info/METADATA',
+        'license_pep639-1.0.0.dist-info/RECORD',
+        'license_pep639-1.0.0.dist-info/WHEEL',
+        'license_pep639-1.0.0.dist-info/licenses/LICENSES/BSD-3-Clause.txt',
+        'license_pep639-1.0.0.dist-info/licenses/LICENSES/MIT.txt',
+    }
+
+    assert metadata(artifact.read('license_pep639-1.0.0.dist-info/METADATA')) == metadata(textwrap.dedent('''\
+        Metadata-Version: 2.4
+        Name: license-pep639
+        Version: 1.0.0
+        License-Expression: MIT OR BSD-3-Clause
+        License-File: LICENSES/BSD-3-Clause.txt
+        License-File: LICENSES/MIT.txt
+    '''))
+
+
 @pytest.mark.skipif(sys.platform not in {'linux', 'darwin'}, reason='Not supported on this platform')
 def test_contents(package_library, wheel_library):
     artifact = wheel.wheelfile.WheelFile(wheel_library)