fix: normalize license expression

Signed-off-by: Henry Schreiner <[email protected]>

.pre-commit-config.yaml

@@ -82,7 +82,7 @@ repos:
           - ninja
           - nox
           - orjson
-          - packaging
+          - packaging>=24.2
           - pytest
           - pytest-subprocess
           - rich

src/scikit_build_core/build/metadata.py

@@ -91,4 +91,17 @@ def get_standard_metadata(
         msg = "Multiple lines in project.description are not supported; this is supposed to be a one line summary"
         raise ValueError(msg)
 
+    # Validate license if possible.
+    if isinstance(metadata.license, str):
+        try:
+            import packaging.licenses
+
+            metadata.license = packaging.licenses.canonicalize_license_expression(
+                metadata.license
+            )
+        except ImportError:
+            logger.warning(
+                "Packaging 24.2+ required for license normalization. Please update (Python 3.8+ required)"
+            )
+
     return metadata

tests/test_prepare_metadata.py

@@ -77,3 +77,14 @@ def test_multiline_description():
         },
         settings=ScikitBuildSettings(minimum_version=Version("0.8")),
     )
+
+
+def test_license_normalization():
+    pytest.importorskip("packaging.licenses")
+    metadata = get_standard_metadata(
+        pyproject_dict={
+            "project": {"name": "hello", "version": "1.1.1", "license": "ApacHE-2.0"}
+        },
+        settings=ScikitBuildSettings(),
+    )
+    assert metadata.license == "Apache-2.0"