fix: properly handle errors in list_tasks JSON-RPC

[ishymko]

Fixes #697 (comment).

Follow-up for #697.

Re #559.

[gemini-code-assist]

Summary of Changes

Hello @ishymko, 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 addresses a deficiency in the list_tasks JSON-RPC endpoint's error handling mechanism. Previously, ServerError exceptions were caught but resulted in an empty or incomplete error response. The updated implementation ensures that when such an error occurs, a structured and informative error message is returned to the client, improving the robustness and debuggability of the API.

Highlights

• Improved Error Handling: The list_tasks JSON-RPC endpoint now correctly handles ServerError exceptions by constructing a proper error response using _build_error_response, ensuring that specific error details or a generic InternalError are returned.

Changelog

• src/a2a/server/request_handlers/jsonrpc_handler.py
  • Modified the list_tasks function to properly handle ServerError exceptions by calling _build_error_response with the specific error or an InternalError.

Activity

• This pull request is a follow-up to a discussion on pull request chore: merge proto refactor into 1.0-dev #697 regarding error handling.
• It addresses a specific issue identified in the discussion at chore: merge proto refactor into 1.0-dev #697 (comment).
• The changes are also related to issue [Feat]: Upgrade A2A to v1.0 #559.

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[gemini-code-assist]

Code Review

This pull request aims to fix error handling in the list_tasks JSON-RPC method. While it correctly identifies a part of the code that needed fixing, the implementation introduces a NameError because request_id is not defined. Additionally, it creates a type inconsistency where the method is declared to return a ListTasksResponse but would return a dict on error. My review provides a suggestion to fix the NameError and recommends a more thorough refactoring to align list_tasks with other methods in the class for consistency and correctness.

[gemini-code-assist]

This change introduces a NameError because request_id is not defined in this scope. It also creates a type inconsistency: this method is declared to return ListTasksResponse, but _build_error_response returns a dict. This will cause issues with static type checking and potentially at runtime depending on how the return value is used.

The list_tasks method seems inconsistent with other methods in this class, which return a dict for the JSON-RPC response on both success and failure. To fix this properly, list_tasks should be refactored to align with the others. This would involve:

1. Changing the return type hint to dict[str, Any].
2. Getting request_id at the start of the method.
3. Wrapping the success result in _build_success_response.

The suggestion below provides a minimal fix for the NameError. The type inconsistency will remain and should be addressed.

Suggested change

	except ServerError as e:
	return _build_error_response(
	request_id, e.error if e.error else InternalError()
	)
	except ServerError as e:
	request_id = self._get_request_id(context)
	return _build_error_response(
	request_id, e.error if e.error else InternalError()
	)

[holtskinner]

You might need to add another option for an error. Note, the other methods like on_get_task() return dicts.

Suggested change

	) -> ListTasksResponse | JSONRPCError:

Double check what the correct type is for _build_error_response