fixups from code-review suggestions

src/packaging/licenses/__init__.py

@@ -32,7 +32,7 @@
 from __future__ import annotations
 
 import re
-from typing import NewType
+from typing import NewType, cast
 
 from packaging.licenses._spdx import EXCEPTIONS, LICENSES
 
@@ -69,7 +69,7 @@ def canonicalize_license_expression(
     license_expression = raw_license_expression.replace("(", " ( ").replace(")", " ) ")
     licenseref_prefix = "LicenseRef-"
     license_refs = {
-        ref.lower(): "LicenseRef-" + ref[len(licenseref_prefix):]
+        ref.lower(): "LicenseRef-" + ref[len(licenseref_prefix) :]
         for ref in license_expression.split()
         if ref.lower().startswith(licenseref_prefix.lower())
     }
@@ -139,4 +139,7 @@ def canonicalize_license_expression(
 
     normalized_expression = " ".join(normalized_tokens)
 
-    return normalized_expression.replace("( ", "(").replace(" )", ")")
+    return cast(
+        NormalizedLicenseExpression,
+        normalized_expression.replace("( ", "(").replace(" )", ")"),
+    )

src/packaging/metadata.py

@@ -19,6 +19,7 @@
 
 from . import licenses, requirements, specifiers, utils
 from . import version as version_module
+from .licenses import NormalizedLicenseExpression
 
 T = typing.TypeVar("T")
 
@@ -644,7 +645,9 @@ def _process_requires_dist(
         else:
             return reqs
 
-    def _process_license_expression(self, value: str) -> NormalizedLicenseExpression | None:
+    def _process_license_expression(
+        self, value: str
+    ) -> NormalizedLicenseExpression | None:
         try:
             return licenses.canonicalize_license_expression(value)
         except ValueError as exc:
@@ -816,7 +819,9 @@ def from_email(cls, data: bytes | str, *, validate: bool = True) -> Metadata:
     """:external:ref:`core-metadata-maintainer-email`"""
     license: _Validator[str | None] = _Validator()
     """:external:ref:`core-metadata-license`"""
-    license_expression: _Validator[NormalizedLicenseExpression | None] = _Validator(added="2.4")
+    license_expression: _Validator[NormalizedLicenseExpression | None] = _Validator(
+        added="2.4"
+    )
     """:external:ref:`core-metadata-license-expression`"""
     license_files: _Validator[list[str] | None] = _Validator(added="2.4")
     """:external:ref:`core-metadata-license-file`"""