fix(grpc): Fix inconsistent property name between gRPC and JSON-RPC in Message object

[a2a-bot]

Commit: a2aproject/A2A@2a1f819

[gemini-code-assist]

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 significantly enhances the A2A service API by integrating a new ListTasks RPC method. This addition provides a robust mechanism for clients to query and manage tasks more effectively, offering capabilities for filtering, pagination, and control over the level of detail returned. The changes span across the protobuf definitions, generated Python code, and the Python type definitions to fully support this new functionality.

Highlights

• New ListTasks RPC Method: A new ListTasks RPC method has been introduced to the A2AService, enabling clients to retrieve a paginated and filterable list of tasks.
• Task Filtering and Pagination: The ListTasks method supports various filtering criteria such as context_id, status, last_updated_time, and includes options for pagination (page_size, page_token) and artifact inclusion (include_artifacts).
• Python Type Hinting and Optimization: The generated Python protobuf interface file (a2a_pb2.pyi) has been updated to reflect the new ListTasks types and includes an optimization by setting __slots__ = () for many message classes, which can reduce memory consumption.
• Message Content Field Renamed: The content field within the Message class in the Python protobuf interface (a2a_pb2.pyi) has been renamed to parts.

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[gemini-code-assist]

Code Review

This pull request updates the A2A specification, primarily by renaming the content field to parts within the Message object and introducing a new ListTasks RPC. The changes across the generated protobuf files and Pydantic type definitions appear consistent with these updates. My review highlights opportunities to enhance data validation in the new Pydantic models and points out some structural redundancies that could be simplified. More critically, I've noted that while the ListTasks RPC is now defined, its server-side and client-side implementations are missing, rendering the feature incomplete. These omissions are flagged as high-severity issues that need to be addressed.

[gemini-code-assist]

The ListTasks RPC has been added to the client stub, but there appears to be no corresponding list_tasks method in a2a.client.transports.grpc.GrpcTransport or the abstract a2a.client.client.Client class. This functionality needs to be exposed to be usable by clients.

[gemini-code-assist]

The ListTasks RPC method has been added to the service definition, but the implementation is missing from the GrpcHandler class in src/a2a/server/request_handlers/grpc_handler.py. Without this, the server will return an UNIMPLEMENTED error for this call.

[gemini-code-assist]

This union is redundant. The type for the RootModel is already defined in the class's generic type parameter (lines 1756-1768). This root attribute with its type hint should be removed to avoid redundancy and simplify the class definition. The same issue exists for the JSONRPCResponse class (defined around line 2102).

[gemini-code-assist]

The docstring for history_length states that it must be non-negative. This constraint can be enforced at the model level using Pydantic's Field for better data validation and clarity.

Suggested change

	history_length: int | None = None
	history_length: int | None = Field(default=None, ge=0)

[gemini-code-assist]

The docstring for page_size specifies a range of 1 to 100. It's a good practice to enforce this validation directly in the Pydantic model using Field to ensure data integrity.

Suggested change

	page_size: int | None = None
	page_size: int | None = Field(default=None, ge=1, le=100)