serialization filter: any one expressen preferred

cyclonedx/model/component.py

@@ -36,7 +36,7 @@
     SchemaVersion1Dot3,
     SchemaVersion1Dot4,
 )
-from ..serialization import BomRefHelper, PackageUrl
+from ..serialization import BomRefHelper, LicensesHelper, PackageUrl
 from . import (
     AttachedText,
     ComparableTuple,
@@ -1028,11 +1028,12 @@ def hashes(self, hashes: Iterable[HashType]) -> None:
         self._hashes = SortedSet(hashes)
 
     @property  # type: ignore[misc]
+    @serializable.type_mapping(LicensesHelper)
     @serializable.view(SchemaVersion1Dot1)
     @serializable.view(SchemaVersion1Dot2)
     @serializable.view(SchemaVersion1Dot3)
     @serializable.view(SchemaVersion1Dot4)
-    @serializable.xml_array(serializable.XmlArraySerializationType.FLAT, 'licenses')
+    # @serializable.xml_array(serializable.XmlArraySerializationType.NESTED, '')
     @serializable.xml_sequence(10)
     def licenses(self) -> "SortedSet[LicenseChoice]":
         """

cyclonedx/serialization/__init__.py

@@ -18,12 +18,15 @@
 Set of helper classes for use with ``serializable`` when conducting (de-)serialization.
 """
 
+import warnings
+from typing import List
 from uuid import UUID
 
 # See https://github.com/package-url/packageurl-python/issues/65
 from packageurl import PackageURL
 from serializable.helpers import BaseHelper
 
+from ..model import LicenseChoice
 from ..model.bom_ref import BomRef
 
 
@@ -76,3 +79,23 @@ def deserialize(cls, o: object) -> UUID:
             return UUID(str(o))
         except ValueError:
             raise ValueError(f'UUID string supplied ({o}) does not parse!')
+
+
+class LicensesHelper(BaseHelper):
+
+    @classmethod
+    def serialize(cls, o: object) -> List[LicenseChoice]:
+        # need to call `list(o)`, because `o` could be any iterable.
+        licenses: List[LicenseChoice] = list(o)  # type: ignore[call-overload]
+        if len(licenses) > 1:
+            expression = next((license for license in licenses if license.expression), None)
+            if expression:
+                warnings.warn(f'Licenses: found an expression {expression!r}, dropping the rest of: {licenses!r}',
+                              RuntimeWarning)
+                return [expression]
+        return licenses
+
+    @classmethod
+    def deserialize(cls, o: object) -> List[LicenseChoice]:
+        raise NotImplementedError
+        return [LicenseChoice.from_json(data) for data in o]