Add initial support for license expression (PEP 639)

docs/userguide/pyproject_config.rst

@@ -49,7 +49,7 @@ The ``project`` table contains metadata fields as described by the
    readme = "README.rst"
    requires-python = ">=3.8"
    keywords = ["one", "two"]
-   license = {text = "BSD-3-Clause"}
+   license = "BSD-3-Clause"
    classifiers = [
        "Framework :: Django",
        "Programming Language :: Python :: 3",

newsfragments/4706.feature.rst

@@ -0,0 +1 @@
+Added initial support for license expression (`PEP 639 <https://peps.python.org/pep-0639/#add-license-expression-field>`_). -- by :user:`cdce8p`

pyproject.toml

@@ -11,10 +11,10 @@ authors = [
 ]
 description = "Easily download, build, install, upgrade, and uninstall Python packages"
 readme = "README.rst"
+license = "MIT"
 classifiers = [
 	"Development Status :: 5 - Production/Stable",
 	"Intended Audience :: Developers",
-	"License :: OSI Approved :: MIT License",
 	"Programming Language :: Python :: 3",
 	"Programming Language :: Python :: 3 :: Only",
 	"Topic :: Software Development :: Libraries :: Python Modules",

setuptools/_core_metadata.py

@@ -87,6 +87,7 @@ def read_pkg_file(self, file):
     self.url = _read_field_from_msg(msg, 'home-page')
     self.download_url = _read_field_from_msg(msg, 'download-url')
     self.license = _read_field_unescaped_from_msg(msg, 'license')
+    self.license_expression = _read_field_unescaped_from_msg(msg, 'license_expression')
 
     self.long_description = _read_field_unescaped_from_msg(msg, 'description')
     if self.long_description is None and self.metadata_version >= Version('2.1'):
@@ -174,7 +175,7 @@ def write_field(key, value):
         if attr_val is not None:
             write_field(field, attr_val)
 
-    license = self.get_license()
+    license = self.license_expression or self.get_license()
     if license:
         write_field('License', rfc822_escape(license))
 

setuptools/config/_apply_pyprojecttoml.py

@@ -31,7 +31,7 @@
     from setuptools._importlib import metadata
     from setuptools.dist import Distribution
 
     from distutils.dist import _OptionsList  # Comes from typeshed
 
 
 EMPTY: Mapping = MappingProxyType({})  # Immutable dict-like
@@ -57,6 +57,7 @@
     os.chdir(root_dir)
     try:
         dist._finalize_requires()
+        dist._finalize_license_expression()
         dist._finalize_license_files()
     finally:
         os.chdir(current_directory)
@@ -174,14 +175,17 @@
         dist._referenced_files.add(file)
 
 
-def _license(dist: Distribution, val: dict, root_dir: StrPath | None):
+def _license(dist: Distribution, val: str | dict, root_dir: StrPath | None):
     from setuptools.config import expand
 
-    if "file" in val:
-        _set_config(dist, "license", expand.read_files([val["file"]], root_dir))
-        dist._referenced_files.add(val["file"])
+    if isinstance(val, str):
+        _set_config(dist, "license_expression", val)
     else:
-        _set_config(dist, "license", val["text"])
+        if "file" in val:
+            _set_config(dist, "license", expand.read_files([val["file"]], root_dir))
+            dist._referenced_files.add(val["file"])
+        else:
+            _set_config(dist, "license", val["text"])
 
 
 def _people(dist: Distribution, val: list[dict], _root_dir: StrPath | None, kind: str):
@@ -345,7 +349,7 @@
     >>> _attrgetter("d")(obj) is None
     True
     """
     return partial(reduce, lambda acc, x: getattr(acc, x, None), attr.split("."))
 
 
 def _some_attrgetter(*items):

setuptools/config/_validate_pyproject/NOTICE

@@ -1,7 +1,7 @@
 The code contained in this directory was automatically generated using the
 following command:
 
-    python -m validate_pyproject.pre_compile --output-dir=setuptools/config/_validate_pyproject --enable-plugins setuptools distutils --very-verbose -t distutils=setuptools/config/distutils.schema.json -t setuptools=setuptools/config/setuptools.schema.json
+    python -m validate_pyproject.pre_compile --output-dir=setuptools/config/_validate_pyproject --enable-plugins setuptools distutils --very-verbose -t setuptools=setuptools/config/setuptools.schema.json -t distutils=setuptools/config/distutils.schema.json
 
 Please avoid changing it manually.
 

setuptools/config/_validate_pyproject/extra_validations.py

@@ -24,6 +24,13 @@ class RedefiningStaticFieldAsDynamic(ValidationError):
     )
 
 
+class IncludedDependencyGroupMustExist(ValidationError):
+    _DESC = """An included dependency group must exist and must not be cyclic.
+    """
+    __doc__ = _DESC
+    _URL = "https://peps.python.org/pep-0735/"
+
+
 def validate_project_dynamic(pyproject: T) -> T:
     project_table = pyproject.get("project", {})
     dynamic = project_table.get("dynamic", [])
@@ -49,4 +56,27 @@ def validate_project_dynamic(pyproject: T) -> T:
     return pyproject
 
 
-EXTRA_VALIDATIONS = (validate_project_dynamic,)
+def validate_include_depenency(pyproject: T) -> T:
+    dependency_groups = pyproject.get("dependency-groups", {})
+    for key, value in dependency_groups.items():
+        for each in value:
+            if (
+                isinstance(each, dict)
+                and (include_group := each.get("include-group"))
+                and include_group not in dependency_groups
+            ):
+                raise IncludedDependencyGroupMustExist(
+                    message=f"The included dependency group {include_group} doesn't exist",
+                    value=each,
+                    name=f"data.dependency_groups.{key}",
+                    definition={
+                        "description": cleandoc(IncludedDependencyGroupMustExist._DESC),
+                        "see": IncludedDependencyGroupMustExist._URL,
+                    },
+                    rule="PEP 735",
+                )
+    # TODO: check for `include-group` cycles (can be conditional to graphlib)
+    return pyproject
+
+
+EXTRA_VALIDATIONS = (validate_project_dynamic, validate_include_depenency)

setuptools/config/_validate_pyproject/formats.py

@@ -164,12 +164,15 @@ class _TroveClassifier:
     """
 
     downloaded: typing.Union[None, "Literal[False]", typing.Set[str]]
+    """
+    None => not cached yet
+    False => unavailable
+    set => cached values
+    """
 
     def __init__(self) -> None:
         self.downloaded = None
         self._skip_download = False
-        # None => not cached yet
-        # False => cache not available
         self.__name__ = "trove_classifier"  # Emulate a public function
 
     def _disable_download(self) -> None:
@@ -351,7 +354,7 @@ def python_entrypoint_reference(value: str) -> bool:
         obj = rest
 
     module_parts = module.split(".")
-    identifiers = _chain(module_parts, obj.split(".")) if rest else module_parts
+    identifiers = _chain(module_parts, obj.split(".")) if rest else iter(module_parts)
     return all(python_identifier(i.strip()) for i in identifiers)
 
 
@@ -373,3 +376,27 @@ def uint(value: builtins.int) -> bool:
 def int(value: builtins.int) -> bool:
     r"""Signed 64-bit integer (:math:`-2^{63} \leq x < 2^{63}`)"""
     return -(2**63) <= value < 2**63
+
+
+try:
+    from packaging import licenses as _licenses
+
+    def SPDX(value: str) -> bool:
+        """See :ref:`PyPA's License-Expression specification
+        <pypa:core-metadata-license-expression>` (added in :pep:`639`).
+        """
+        try:
+            _licenses.canonicalize_license_expression(value)
+            return True
+        except _licenses.InvalidLicenseExpression:
+            return False
+
+except ImportError:  # pragma: no cover
+    _logger.warning(
+        "Could not find an up-to-date installation of `packaging`. "
+        "License expressions might not be validated. "
+        "To enforce validation, please install `packaging>=24.2`."
+    )
+
+    def SPDX(value: str) -> bool:
+        return True

setuptools/dist.py

@@ -12,6 +12,7 @@
 from typing import TYPE_CHECKING, Any, Union
 
 from more_itertools import partition, unique_everseen
+from packaging.licenses import canonicalize_license_expression
 from packaging.markers import InvalidMarker, Marker
 from packaging.specifiers import InvalidSpecifier, SpecifierSet
 from packaging.version import Version
@@ -26,6 +27,7 @@
 from ._reqs import _StrOrIter
 from .config import pyprojecttoml, setupcfg
 from .discovery import ConfigDiscovery
+from .errors import InvalidConfigError
 from .monkey import get_unpatched
 from .warnings import InformationOnly, SetuptoolsDeprecationWarning
 
@@ -288,6 +290,7 @@ class Distribution(_Distribution):
         'long_description_content_type': lambda: None,
         'project_urls': dict,
         'provides_extras': dict,  # behaves like an ordered set
+        'license_expression': lambda: None,
         'license_file': lambda: None,
         'license_files': lambda: None,
         'install_requires': list,
@@ -397,6 +400,23 @@ def _normalize_requires(self):
             k: list(map(str, _reqs.parse(v or []))) for k, v in extras_require.items()
         }
 
+    def _finalize_license_expression(self) -> None:
+        """Normalize license and license_expression."""
+        license_expr = self.metadata.license_expression
+        if license_expr:
+            normalized = canonicalize_license_expression(license_expr)
+            if license_expr != normalized:
+                InformationOnly.emit(f"Normalizing '{license_expr}' to '{normalized}'")
+                self.metadata.license_expression = normalized
+
+            for cl in self.metadata.get_classifiers():
+                if not cl.startswith("License :: "):
+                    continue
+                raise InvalidConfigError(
+                    "License classifier are deprecated in favor of the license expression. "
+                    f"Remove the '{cl}' classifier."
+                )
+
     def _finalize_license_files(self) -> None:
         """Compute names of all license files which should be included."""
         license_files: list[str] | None = self.metadata.license_files
@@ -648,6 +668,7 @@ def parse_config_files(
             pyprojecttoml.apply_configuration(self, filename, ignore_option_errors)
 
         self._finalize_requires()
+        self._finalize_license_expression()
         self._finalize_license_files()
 
     def fetch_build_eggs(

setuptools/tests/config/test_apply_pyprojecttoml.py

@@ -22,7 +22,7 @@
 from setuptools.config import expand, pyprojecttoml, setupcfg
 from setuptools.config._apply_pyprojecttoml import _MissingDynamic, _some_attrgetter
 from setuptools.dist import Distribution
-from setuptools.errors import RemovedConfigError
+from setuptools.errors import InvalidConfigError, RemovedConfigError
 
 from .downloads import retrieve_file, urls_from_file
 
@@ -155,6 +155,31 @@ def main_gui(): pass
 def main_tomatoes(): pass
 """
 
+PEP639_LICENSE_TEXT = """\
+[project]
+name = "spam"
+version = "2020.0.0"
+authors = [
+  {email = "hi@pradyunsg.me"},
+  {name = "Tzu-Ping Chung"}
+]
+license = {text = "MIT"}
+"""
+
+PEP639_LICENSE_EXPRESSION = """\
+[project]
+name = "spam"
+version = "2020.0.0"
+authors = [
+  {email = "hi@pradyunsg.me"},
+  {name = "Tzu-Ping Chung"}
+]
+license = "mit or apache-2.0"  # should be normalized in metadata
+classifiers = [
+    "Development Status :: 5 - Production/Stable",
+]
+"""
+
 
 def _pep621_example_project(
     tmp_path,
@@ -250,10 +275,60 @@ def test_utf8_maintainer_in_metadata(  # issue-3663
     assert f"Maintainer-email: {expected_maintainers_meta_value}" in content
 
 
-class TestLicenseFiles:
-    # TODO: After PEP 639 is accepted, we have to move the license-files
-    #       to the `project` table instead of `tool.setuptools`
+@pytest.mark.parametrize(
+    ('pyproject_text', 'license', 'license_expression', 'content_str'),
+    (
+        pytest.param(
+            PEP639_LICENSE_TEXT,
+            'MIT',
+            None,
+            'License: MIT',
+            id='license-text',
+        ),
+        pytest.param(
+            PEP639_LICENSE_EXPRESSION,
+            None,
+            'MIT OR Apache-2.0',
+            'License: MIT OR Apache-2.0',  # TODO Metadata version '2.4'
+            id='license-expression',
+        ),
+    ),
+)
+def test_license_in_metadata(
+    license,
+    license_expression,
+    content_str,
+    pyproject_text,
+    tmp_path,
+):
+    pyproject = _pep621_example_project(
+        tmp_path,
+        "README",
+        pyproject_text=pyproject_text,
+    )
+    dist = pyprojecttoml.apply_configuration(makedist(tmp_path), pyproject)
+    assert dist.metadata.license == license
+    assert dist.metadata.license_expression == license_expression
+    pkg_file = tmp_path / "PKG-FILE"
+    with open(pkg_file, "w", encoding="utf-8") as fh:
+        dist.metadata.write_pkg_file(fh)
+    content = pkg_file.read_text(encoding="utf-8")
+    assert content_str in content
+
 
+def test_license_expression_with_bad_classifier(tmp_path):
+    text = PEP639_LICENSE_EXPRESSION.rsplit("\n", 2)[0]
+    pyproject = _pep621_example_project(
+        tmp_path,
+        "README",
+        f"{text}\n    \"License :: OSI Approved :: MIT License\"\n]",
+    )
+    msg = "License classifier are deprecated.*'License :: OSI Approved :: MIT License'"
+    with pytest.raises(InvalidConfigError, match=msg):
+        pyprojecttoml.apply_configuration(makedist(tmp_path), pyproject)
+
+
+class TestLicenseFiles:
     def base_pyproject(self, tmp_path, additional_text):
         pyproject = _pep621_example_project(tmp_path, "README")
         text = pyproject.read_text(encoding="utf-8")
@@ -266,6 +341,24 @@ def base_pyproject(self, tmp_path, additional_text):
         pyproject.write_text(text, encoding="utf-8")
         return pyproject
 
+    def base_pyproject_license_pep639(self, tmp_path):
+        pyproject = _pep621_example_project(tmp_path, "README")
+        text = pyproject.read_text(encoding="utf-8")
+
+        # Sanity-check
+        assert 'license = {file = "LICENSE.txt"}' in text
+        assert 'license-files' not in text
+        assert "[tool.setuptools]" not in text
+
+        text = re.sub(
+            r"(license = {file = \"LICENSE.txt\"})\n",
+            ("license = \"licenseref-Proprietary\"\nlicense-files = [\"_FILE*\"]\n"),
+            text,
+            count=1,
+        )
+        pyproject.write_text(text, encoding="utf-8")
+        return pyproject
+
     def test_both_license_and_license_files_defined(self, tmp_path):
         setuptools_config = '[tool.setuptools]\nlicense-files = ["_FILE*"]'
         pyproject = self.base_pyproject(tmp_path, setuptools_config)
@@ -282,6 +375,18 @@ def test_both_license_and_license_files_defined(self, tmp_path):
         assert set(dist.metadata.license_files) == {"_FILE.rst", "_FILE.txt"}
         assert dist.metadata.license == "LicenseRef-Proprietary\n"
 
+    def test_both_license_and_license_files_defined_pep639(self, tmp_path):
+        # Set license and license-files
+        pyproject = self.base_pyproject_license_pep639(tmp_path)
+
+        (tmp_path / "_FILE.txt").touch()
+        (tmp_path / "_FILE.rst").touch()
+
+        dist = pyprojecttoml.apply_configuration(makedist(tmp_path), pyproject)
+        assert set(dist.metadata.license_files) == {"_FILE.rst", "_FILE.txt"}
+        assert dist.metadata.license is None
+        assert dist.metadata.license_expression == "LicenseRef-Proprietary"
+
     def test_default_patterns(self, tmp_path):
         setuptools_config = '[tool.setuptools]\nzip-safe = false'
         # ^ used just to trigger section validation

tox.ini

@@ -83,7 +83,7 @@ commands =
 [testenv:generate-validation-code]
 skip_install = True
 deps =
-	validate-pyproject[all]==0.19
+	validate-pyproject[all]==0.23
 commands =
 	python -m tools.generate_validation_code