BUG: adjust to older pyproject-metadata releases

mesonpy/__init__.py

@@ -78,6 +78,8 @@ def canonicalize_license_expression(s: str) -> str:
 
 __version__ = '0.17.0.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
@@ -272,7 +274,7 @@ def from_pyproject(
  'Required "project.version" field is missing and not declared as dynamic')
 
  # Check for unsupported dynamic fields.
- unsupported_dynamic = set(metadata.dynamic) - {'version', 'license', 'license-files'}
+ 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}')
@@ -759,7 +761,12 @@ def __init__(
  if license is None:
  raise pyproject_metadata.ConfigurationError(
  'Field "license" declared as dynamic but license is not specified in meson.build')
- self._metadata.license = license
+ # 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:
@@ -768,9 +775,11 @@ def __init__(
  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),
- license=self._meson_license, license_files=self._meson_license_files)
+ 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:
@@ -909,7 +918,7 @@ def _meson_license(self) -> Optional[str]:
  assert isinstance(value, str)
  if value == 'unknown':
  return None
- return canonicalize_license_expression(value)
+ return str(canonicalize_license_expression(value)) # str() is to make mypy happy
 
  @property
  def _meson_license_files(self) -> Optional[List[pathlib.Path]]: