feat(compat): set a2a-version header to 1.0.0

[bartek-w]

Description

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[gemini-code-assist]

Summary of Changes

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This pull request enhances the client's communication by automatically including a protocol version header in all requests. This change standardizes how the client identifies its protocol version to services, which is crucial for maintaining compatibility and enabling future API evolution. It ensures that both HTTPX and gRPC clients consistently send this version information, improving robustness and clarity in client-server interactions.

Highlights

• Protocol Versioning: Introduced a new X-A2A-Version header, set to 1.0.0, to explicitly communicate the protocol version in all outgoing HTTPX and gRPC requests.
• Client Initialization: Ensured that an httpx.AsyncClient is always initialized within the ClientFactory and its headers are configured with the protocol version, preventing potential None references.
• gRPC Metadata: Modified the gRPC transport layer to automatically include the X-A2A-Version header in all gRPC metadata, standardizing version communication across different transport protocols.
• Constant Definitions: Defined new constants (VERSION_HEADER, PROTOCOL_VERSION_1_0, PROTOCOL_VERSION_CURRENT) to centralize and manage protocol version information.
• Test Coverage: Updated existing gRPC client tests and added new constant tests to verify the correct application and assertion of the X-A2A-Version header in various scenarios.

Changelog

• src/a2a/client/client_factory.py
  • Imported PROTOCOL_VERSION_CURRENT and VERSION_HEADER constants.
  • Modified __init__ to ensure config.httpx_client is initialized and sets the X-A2A-Version header.
  • Updated _register_defaults to consistently use the configured httpx_client.
  • Modified connect to set the X-A2A-Version header when resolving agent cards.
• src/a2a/client/transports/grpc.py
  • Imported PROTOCOL_VERSION_CURRENT and VERSION_HEADER constants.
  • Modified _get_grpc_metadata to include the X-A2A-Version header in gRPC request metadata.
• src/a2a/utils/constants.py
  • Added VERSION_HEADER, PROTOCOL_VERSION_1_0, and PROTOCOL_VERSION_CURRENT constants.
• tests/client/transports/test_grpc_client.py
  • Imported VERSION_HEADER and PROTOCOL_VERSION_CURRENT constants.
  • Removed unused imports a2a_pb2_grpc and ListTaskPushNotificationConfigsResponse.
  • Removed unused import proto_utils.
  • Updated various gRPC client tests to assert the presence and value of the X-A2A-Version header in request metadata.
  • Modified test_get_grpc_metadata to include the version header in expected metadata.
• tests/utils/test_constants.py
  • Added test_version_header to verify the VERSION_HEADER constant.
  • Added test_protocol_versions to verify the PROTOCOL_VERSION_1_0 and PROTOCOL_VERSION_CURRENT constants.

Activity

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• The pull request title follows the conventional commits specification, indicating a new feature (feat).
• The author has ensured that tests and linter checks pass.
• The author has confirmed that appropriate documentation updates were considered (if necessary).

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[gemini-code-assist]

Code Review

This pull request adds the X-A2A-Version header to outgoing requests, which is a good step for protocol compatibility. The implementation looks mostly correct, with changes across HTTP and gRPC transports. I've left a couple of suggestions: one to improve code clarity by removing a redundant operation in the ClientFactory, and another to correct a type hint in the gRPC transport to align with the new logic and repository style guide.