ENH: add support for licence and license-files dynamic fields

Fixes mesonbuild#270.

Author: dnicolodi

docs/reference/meson-compatibility.rst

@@ -39,6 +39,14 @@ versions.
    Meson 1.3.0 or later is required for compiling extension modules
    targeting the Python limited API.
 
+.. option:: 1.6.0
+
+   Meson 1.6.0 or later is required to support ``license`` and
+   ``license-files`` dynamic fields in ``pyproject.toml`` and to
+   populate the package license and license files from the ones
+   declared via the ``project()`` call in ``meson.build``. This also
+   requires ``pyproject-metadata`` version 0.9.0 or later.
+
 Build front-ends by default build packages in an isolated Python
 environment where build dependencies are installed. Most often, unless
 a package or its build dependencies declare explicitly a version

mesonpy/__init__.py

@@ -78,6 +78,8 @@ def canonicalize_license_expression(s: str) -> str:
 
 __version__ = '0.18.0.dev0'
 
+_PYPROJECT_METADATA_VERSION = tuple(map(int, pyproject_metadata.__version__.split('.')[:2]))
+_SUPPORTED_DYNAMIC_FIELDS = {'version', } if _PYPROJECT_METADATA_VERSION < (0, 9) else {'version', 'license', 'license-files'}
 
 _NINJA_REQUIRED_VERSION = '1.8.2'
 _MESON_REQUIRED_VERSION = '0.63.3' # keep in sync with the version requirement in pyproject.toml
@@ -260,7 +262,7 @@ def from_pyproject(
         metadata = super().from_pyproject(data, project_dir, metadata_version)
 
         # Check for unsupported dynamic fields.
-        unsupported_dynamic = set(metadata.dynamic) - {'version', }
+        unsupported_dynamic = set(metadata.dynamic) - _SUPPORTED_DYNAMIC_FIELDS
         if unsupported_dynamic:
             fields = ', '.join(f'"{x}"' for x in unsupported_dynamic)
             raise pyproject_metadata.ConfigurationError(f'Unsupported dynamic fields: {fields}')
@@ -731,13 +733,30 @@ def __init__(
                     raise pyproject_metadata.ConfigurationError(
                         'Field "version" declared as dynamic but version is not defined in meson.build')
                 self._metadata.version = packaging.version.Version(version)
+            if 'license' in self._metadata.dynamic:
+                license = self._meson_license
+                if license is None:
+                    raise pyproject_metadata.ConfigurationError(
+                        'Field "license" declared as dynamic but license is not specified in meson.build')
+                # mypy is not happy when analyzing typing based on
+                # pyproject-metadata < 0.9 where license needs to be of
+                # License type.  However, this code is not executed if
+                # pyproject-metadata is older than 0.9 because then dynamic
+                # license is not allowed.
+                self._metadata.license = license  # type: ignore[assignment]
+            if 'license-files' in self._metadata.dynamic:
+                self._metadata.license_files = self._meson_license_files
         else:
             # if project section is missing, use minimal metdata from meson.build
             name, version = self._meson_name, self._meson_version
             if version is None:
                 raise pyproject_metadata.ConfigurationError(
                     'Section "project" missing in pyproject.toml and version is not defined in meson.build')
-            self._metadata = Metadata(name=name, version=packaging.version.Version(version))
+            kwargs = {
+                'license': self._meson_license,
+                'license_files': self._meson_license_files
+            } if _PYPROJECT_METADATA_VERSION >= (0, 9) else {}
+            self._metadata = Metadata(name=name, version=packaging.version.Version(version), **kwargs)
 
         # verify that we are running on a supported interpreter
         if self._metadata.requires_python:
@@ -862,6 +881,31 @@ def _meson_version(self) -> Optional[str]:
             return None
         return value
 
+    @property
+    def _meson_license(self) -> Optional[str]:
+        """The license specified with the ``license`` argument to ``project()`` in meson.build."""
+        value = self._info('intro-projectinfo').get('license', None)
+        if value is None:
+            return None
+        assert isinstance(value, list)
+        if len(value) > 1:
+            raise pyproject_metadata.ConfigurationError(
+                'using a list of strings for the license declared in meson.build is ambiguous: use a SPDX license expression')
+        value = value[0]
+        assert isinstance(value, str)
+        if value == 'unknown':
+            return None
+        return str(canonicalize_license_expression(value)) # str() is to make mypy happy
+
+    @property
+    def _meson_license_files(self) -> Optional[List[pathlib.Path]]:
+        """The license files specified with the ``license_files`` argument to ``project()`` in meson.build."""
+        value = self._info('intro-projectinfo').get('license_files', None)
+        if not value:
+            return None
+        assert isinstance(value, list)
+        return [pathlib.Path(x) for x in value]
+
     def sdist(self, directory: Path) -> pathlib.Path:
         """Generates a sdist (source distribution) in the specified directory."""
         # Generate meson dist file.

tests/conftest.py

@@ -18,13 +18,20 @@
 
 import packaging.metadata
 import packaging.version
+import pyproject_metadata
 import pytest
 
 import mesonpy
 
 from mesonpy._util import chdir
 
 
+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]))
+
+
 def metadata(data):
     meta, other = packaging.metadata.parse_email(data)
     # PEP-639 support requires packaging >= 24.1.  Add minimal

tests/test_project.py

@@ -19,7 +19,7 @@
 
 import mesonpy
 
-from .conftest import in_git_repo_context, package_dir
+from .conftest import MESON_VERSION, PYPROJECT_METADATA_VERSION, in_git_repo_context, metadata, package_dir
 
 
 def test_unsupported_python_version(package_unsupported_python_version):
@@ -40,6 +40,94 @@ def test_missing_dynamic_version(package_missing_dynamic_version):
             pass
 
 
+@pytest.mark.skipif(PYPROJECT_METADATA_VERSION < (0, 9), reason='pyproject-metadata too old')
+@pytest.mark.skipif(MESON_VERSION < (1, 6, 0), reason='meson too old')
+@pytest.mark.filterwarnings('ignore:canonicalization and validation of license expression')
+def test_meson_build_metadata(tmp_path):
+    tmp_path.joinpath('pyproject.toml').write_text(textwrap.dedent('''
+        [build-system]
+        build-backend = 'mesonpy'
+        requires = ['meson-python']
+    '''), encoding='utf8')
+
+    tmp_path.joinpath('meson.build').write_text(textwrap.dedent('''
+        project('test', version: '1.2.3', license: 'MIT', license_files: 'LICENSE')
+    '''), encoding='utf8')
+
+    tmp_path.joinpath('LICENSE').write_text('')
+
+    p = mesonpy.Project(tmp_path, tmp_path / 'build')
+
+    assert metadata(bytes(p._metadata.as_rfc822())) == metadata(textwrap.dedent('''\
+        Metadata-Version: 2.4
+        Name: test
+        Version: 1.2.3
+        License-Expression: MIT
+        License-File: LICENSE
+    '''))
+
+
+@pytest.mark.skipif(PYPROJECT_METADATA_VERSION < (0, 9), reason='pyproject-metadata too old')
+@pytest.mark.skipif(MESON_VERSION < (1, 6, 0), reason='meson too old')
+@pytest.mark.filterwarnings('ignore:canonicalization and validation of license expression')
+def test_dynamic_license(tmp_path):
+    tmp_path.joinpath('pyproject.toml').write_text(textwrap.dedent('''
+        [build-system]
+        build-backend = 'mesonpy'
+        requires = ['meson-python']
+
+        [project]
+        name = 'test'
+        version = '1.0.0'
+        dynamic = ['license']
+    '''), encoding='utf8')
+
+    tmp_path.joinpath('meson.build').write_text(textwrap.dedent('''
+        project('test', license: 'MIT')
+    '''), encoding='utf8')
+
+    p = mesonpy.Project(tmp_path, tmp_path / 'build')
+
+    assert metadata(bytes(p._metadata.as_rfc822())) == metadata(textwrap.dedent('''\
+        Metadata-Version: 2.4
+        Name: test
+        Version: 1.0.0
+        License-Expression: MIT
+    '''))
+
+
+@pytest.mark.skipif(PYPROJECT_METADATA_VERSION < (0, 9), reason='pyproject-metadata too old')
+@pytest.mark.skipif(MESON_VERSION < (1, 6, 0), reason='meson too old')
+@pytest.mark.filterwarnings('ignore:canonicalization and validation of license expression')
+def test_dynamic_license_files(tmp_path):
+    tmp_path.joinpath('pyproject.toml').write_text(textwrap.dedent('''
+        [build-system]
+        build-backend = 'mesonpy'
+        requires = ['meson-python']
+
+        [project]
+        name = 'test'
+        version = '1.0.0'
+        dynamic = ['license', 'license-files']
+    '''), encoding='utf8')
+
+    tmp_path.joinpath('meson.build').write_text(textwrap.dedent('''
+        project('test', license: 'MIT', license_files: ['LICENSE'])
+    '''), encoding='utf8')
+
+    tmp_path.joinpath('LICENSE').write_text('')
+
+    p = mesonpy.Project(tmp_path, tmp_path / 'build')
+
+    assert metadata(bytes(p._metadata.as_rfc822())) == metadata(textwrap.dedent('''\
+        Metadata-Version: 2.4
+        Name: test
+        Version: 1.0.0
+        License-Expression: MIT
+        License-File: LICENSE
+    '''))
+
+
 def test_user_args(package_user_args, tmp_path, monkeypatch):
     project_run = mesonpy.Project._run
     cmds = []

tests/test_sdist.py

@@ -17,7 +17,7 @@
 from .conftest import in_git_repo_context, metadata
 
 
-def test_no_pep621(sdist_library):
+def test_meson_build_metadata(sdist_library):
     with tarfile.open(sdist_library, 'r:gz') as sdist:
         sdist_pkg_info = sdist.extractfile('library-1.0.0/PKG-INFO').read()
 
@@ -28,7 +28,7 @@ def test_no_pep621(sdist_library):
     '''))
 
 
-def test_pep621(sdist_full_metadata):
+def test_pep621_metadata(sdist_full_metadata):
     with tarfile.open(sdist_full_metadata, 'r:gz') as sdist:
         sdist_pkg_info = sdist.extractfile('full_metadata-1.2.3/PKG-INFO').read()
 

tests/test_wheel.py

@@ -6,26 +6,19 @@
 import re
 import shutil
 import stat
-import subprocess
 import sys
 import sysconfig
 import textwrap
 
 import packaging.tags
-import pyproject_metadata
 import pytest
 import wheel.wheelfile
 
 import mesonpy
 
-from .conftest import adjust_packaging_platform_tag, metadata
+from .conftest import MESON_VERSION, PYPROJECT_METADATA_VERSION, 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]))
-
 EXT_SUFFIX = sysconfig.get_config_var('EXT_SUFFIX')
 if sys.version_info <= (3, 8, 7):
     if MESON_VERSION >= (0, 99):