fix(proto): Adds metadata field to A2A DataPart proto #455
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Summary of Changes
Hello @a2a-bot, I'm Gemini Code Assist1! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!
This pull request updates the A2A specification by introducing a new metadata field to the Part message within the protobuf definition. This enhancement provides a flexible mechanism to embed arbitrary structured data directly into message parts, significantly improving the extensibility and information richness of A2A messages. The corresponding Python generated files have been updated to incorporate these changes.
Highlights
- Protobuf
Partmessage enhancement: Added ametadatafield of typegoogle.protobuf.Structto thePartmessage in the A2A protobuf definition. This allows for associating arbitrary structured data with individual message parts. - Generated files update: Regenerated the Python protobuf files (
a2a_pb2.pyanda2a_pb2.pyi) to reflect the updated specification, ensuring type safety and correct serialization.
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Code Review
This pull request updates the protobuf specification to add a metadata field to the Part message. While the generated Python files (a2a_pb2.py and a2a_pb2.pyi) correctly reflect this change, a critical piece of logic is missing. The conversion utility in src/a2a/utils/proto_utils.py has not been updated to handle this new field, which will cause the metadata to be lost during serialization and deserialization. This must be addressed before merging.
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Code Review
This pull request adds a metadata field to the Part protobuf message, allowing for metadata to be associated with any type of message part. The changes are correctly reflected in the generated protobuf files. The proto_utils.py file has been updated to handle the new field during type conversions.
My review focuses on improving the maintainability and correctness of the conversion logic in proto_utils.py. I've suggested refactoring the ToProto.part and FromProto.part methods to reduce code duplication. More importantly, I've identified a potential bug in FromProto.part where the check for metadata presence is incorrect, and I've provided a suggestion to fix it while also making the code cleaner.
| def part(cls, part: a2a_pb2.Part) -> types.Part: | ||
| if part.HasField('text'): | ||
| return types.Part(root=types.TextPart(text=part.text)) | ||
| return types.Part( | ||
| root=types.TextPart( | ||
| text=part.text, | ||
| metadata=cls.metadata(part.metadata) | ||
| if part.metadata | ||
| else None, | ||
| ), | ||
| ) | ||
| if part.HasField('file'): | ||
| return types.Part(root=types.FilePart(file=cls.file(part.file))) | ||
| return types.Part( | ||
| root=types.FilePart( | ||
| file=cls.file(part.file), | ||
| metadata=cls.metadata(part.metadata) | ||
| if part.metadata | ||
| else None, | ||
| ), | ||
| ) | ||
| if part.HasField('data'): | ||
| return types.Part(root=types.DataPart(data=cls.data(part.data))) | ||
| return types.Part( | ||
| root=types.DataPart( | ||
| data=cls.data(part.data), | ||
| metadata=cls.metadata(part.metadata) | ||
| if part.metadata | ||
| else None, | ||
| ), | ||
| ) | ||
| raise ValueError(f'Unsupported part type: {part}') |
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The logic for handling metadata is repeated in each branch, and the condition if part.metadata is incorrect because a protobuf message object is always truthy. This means the else None branch is unreachable, and empty metadata will be converted to an empty dictionary {} instead of None. This can be a subtle bug if downstream code expects None.
I suggest refactoring to extract the common metadata handling logic, which also fixes the bug and makes the code more readable and maintainable.
def part(cls, part: a2a_pb2.Part) -> types.Part:
metadata = cls.metadata(part.metadata) if part.metadata.fields else None
if part.HasField('text'):
return types.Part(
root=types.TextPart(
text=part.text,
metadata=metadata,
),
)
if part.HasField('file'):
return types.Part(
root=types.FilePart(
file=cls.file(part.file),
metadata=metadata,
),
)
if part.HasField('data'):
return types.Part(
root=types.DataPart(
data=cls.data(part.data),
metadata=metadata,
),
)
raise ValueError(f'Unsupported part type: {part}')| def part(cls, part: types.Part) -> a2a_pb2.Part: | ||
| if isinstance(part.root, types.TextPart): | ||
| return a2a_pb2.Part(text=part.root.text) | ||
| return a2a_pb2.Part( | ||
| text=part.root.text, metadata=cls.metadata(part.root.metadata) | ||
| ) | ||
| if isinstance(part.root, types.FilePart): | ||
| return a2a_pb2.Part(file=cls.file(part.root.file)) | ||
| return a2a_pb2.Part( | ||
| file=cls.file(part.root.file), | ||
| metadata=cls.metadata(part.root.metadata), | ||
| ) | ||
| if isinstance(part.root, types.DataPart): | ||
| return a2a_pb2.Part(data=cls.data(part.root.data)) | ||
| return a2a_pb2.Part( | ||
| data=cls.data(part.root.data), | ||
| metadata=cls.metadata(part.root.metadata), | ||
| ) | ||
| raise ValueError(f'Unsupported part type: {part.root}') |
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The logic for creating the a2a_pb2.Part is repeated across the different if statements. You can refactor this to be more DRY (Don't Repeat Yourself) by preparing the arguments for a2a_pb2.Part and calling it only once at the end. This improves maintainability.
def part(cls, part: types.Part) -> a2a_pb2.Part:
kwargs = {"metadata": cls.metadata(part.root.metadata)}
if isinstance(part.root, types.TextPart):
kwargs["text"] = part.root.text
elif isinstance(part.root, types.FilePart):
kwargs["file"] = cls.file(part.root.file)
elif isinstance(part.root, types.DataPart):
kwargs["data"] = cls.data(part.root.data)
else:
raise ValueError(f'Unsupported part type: {part.root}')
return a2a_pb2.Part(**kwargs)🤖 I have created a release *beep* *boop* --- ## [0.3.5](v0.3.4...v0.3.5) (2025-09-08) ### Bug Fixes * Prevent client disconnect from stopping task execution ([#440](#440)) ([58b4c81](58b4c81)), closes [#296](#296) * **proto:** Adds metadata field to A2A DataPart proto ([#455](#455)) ([6d0ef59](6d0ef59)) ### Documentation * add example docs for `[@Validate](https://github.com/validate)` and `[@Validate](https://github.com/validate)_async_generator` ([#422](#422)) ([18289eb](18289eb)) * Restructure README ([9758f78](9758f78)) --- This PR was generated with [Release Please](https://github.com/googleapis/release-please). See [documentation](https://github.com/googleapis/release-please#release-please).
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