refactor: Refactor client into BaseClient + ClientTransport #363

mikeas1 · 2025-07-29T20:44:45Z

A refactor of the refactor.

This pulls out the common code from across transport-specific clients into one BaseClient, then shoves all the transport-specific code into implementations of ClientTransport.

gemini-code-assist

Summary of Changes

Hello @mikeas1, 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!

I've undertaken a significant refactoring of the client architecture to improve modularity and maintainability. The core change involves separating the common client logic from the transport-specific communication details. I've introduced a BaseClient to handle shared functionalities and a ClientTransport interface that defines how different protocols interact with the agent. Existing transport implementations have been migrated to adhere to this new ClientTransport interface, and the ClientFactory has been updated to dynamically assemble clients using these new, specialized transport components. This change results in a cleaner, more extensible, and easier-to-maintain client codebase.

Highlights

Introduction of BaseClient: I've introduced a new BaseClient class that encapsulates all the common, transport-agnostic logic previously duplicated across different client implementations. This centralizes shared functionalities like event consumption and task management.
Creation of ClientTransport Interface: To cleanly separate transport-specific concerns, I've defined a new abstract base class, ClientTransport. This interface outlines the methods required for any communication transport (e.g., sending messages, getting tasks, handling streaming).
Migration to Dedicated Transport Implementations: The existing gRPC, JSON-RPC, and REST client implementations have been refactored into new, dedicated GrpcTransport, JsonRpcTransport, and RestTransport classes, respectively. Each of these now implements the ClientTransport interface, handling the specific network communication details for their protocol.
Updated ClientFactory for Modular Client Creation: The ClientFactory has been updated to leverage this new architecture. Instead of creating monolithic client instances, it now selects and instantiates the appropriate ClientTransport based on the agent's capabilities and the client's configuration, and then wraps it within a BaseClient instance. This makes client creation more flexible and extensible.
Removal of Old Client Implementations: The previous, tightly coupled client implementations (grpc_client.py, jsonrpc_client.py, rest_client.py) have been removed, streamlining the codebase and eliminating redundancy.

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gemini-code-assist

Code Review

This pull request introduces a significant and well-executed refactoring of the client architecture, separating transport-independent logic into a BaseClient and isolating protocol-specific details into ClientTransport implementations. This is a great improvement for modularity and extensibility. My review focuses on a few potential issues in the new gRPC transport that could lead to incorrect behavior or resource leaks, and a concern about reduced test coverage for the JSON-RPC transport.

src/a2a/client/transports/grpc.py

tests/client/test_jsonrpc_client.py

src/a2a/client/transports/grpc.py

…ent + server

…nd A2AGrpcClient

mikeas1 · 2025-07-30T04:38:10Z

/gemini review

gemini-code-assist

Code Review

This pull request refactors the client implementation, separating transport-agnostic logic into a BaseClient and transport-specific details into ClientTransport implementations, which improves modularity and maintainability. The addition of an integration test suite is a good step towards ensuring the stability of this new architecture. The RestTransport does not implement interceptors, and there is a large block of duplicated code in one of the new test files.

src/a2a/client/transports/rest.py

gemini-code-assist · 2025-07-30T04:39:46Z

tests/client/test_legacy_client.py

+from unittest.mock import AsyncMock, MagicMock
+
+import httpx
+import pytest
+
+from a2a.client import A2AClient, A2AGrpcClient
+from a2a.types import (
+    AgentCapabilities,
+    AgentCard,
+    GetTaskRequest,
+    Message,
+    MessageSendParams,
+    Part,
+    Role,
+    SendMessageRequest,
+    Task,
+    TaskQueryParams,
+    TaskState,
+    TaskStatus,
+    TextPart,
+)
+
+
+@pytest.fixture
+def mock_httpx_client() -> AsyncMock:
+    return AsyncMock(spec=httpx.AsyncClient)
+
+
+@pytest.fixture
+def mock_grpc_stub() -> AsyncMock:
+    stub = AsyncMock()
+    stub._channel = MagicMock()
+    return stub
+
+
+@pytest.fixture
+def jsonrpc_agent_card() -> AgentCard:
+    return AgentCard(
+        name='Test Agent',
+        description='A test agent',
+        url='http://test.agent.com/rpc',
+        version='1.0.0',
+        capabilities=AgentCapabilities(streaming=True),
+        skills=[],
+        default_input_modes=[],
+        default_output_modes=[],
+        preferred_transport='jsonrpc',
+    )
+
+
+@pytest.fixture
+def grpc_agent_card() -> AgentCard:
+    return AgentCard(
+        name='Test Agent',
+        description='A test agent',
+        url='http://test.agent.com/rpc',
+        version='1.0.0',
+        capabilities=AgentCapabilities(streaming=True),
+        skills=[],
+        default_input_modes=[],
+        default_output_modes=[],
+        preferred_transport='grpc',
+    )
+
+
+@pytest.mark.asyncio
+async def test_a2a_client_send_message(
+    mock_httpx_client: AsyncMock, jsonrpc_agent_card: AgentCard
+):
+    client = A2AClient(
+        httpx_client=mock_httpx_client, agent_card=jsonrpc_agent_card
+    )


This block of code appears to be a copy-paste of the setup code from lines 1-74. This duplication should be removed to improve the test file's clarity and maintainability.

src/a2a/client/transports/base.py

src/a2a/client/legacy.py

refactor: Update client code to support multi-transport refactor: Refactor client into BaseClient + ClientTransport #363 --------- Co-authored-by: pstephengoogle <pstephen@google.com> Co-authored-by: swapydapy <swapnilag@google.com> Co-authored-by: gemini-code-assist[bot] <176961590+gemini-code-assist[bot]@users.noreply.github.com> Co-authored-by: kthota-g <kcthota@google.com> Co-authored-by: Aneesh Garg <1320714+aneeshgarg@users.noreply.github.com> Co-authored-by: Mike Smith <mikeas@google.com>

mikeas1 added 2 commits July 29, 2025 19:34

Gemini authored: refactor clients into BaseClient + ClientTransport

c7f4eb0

Gemini authored: update tests

0289cb7

gemini-code-assist bot reviewed Jul 29, 2025

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mikeas1 added 6 commits July 30, 2025 03:13

Merge branch 'restful' into restful

b31992a

Gemini authored: add an integration test that exercises transport cli…

8e70dc4

…ent + server

Add integration tests, fix uncovered bugs.

d632deb

Fix remaining broken tests

2cd2fcd

Gemini authored: attempt to restore JSON-RPC client tests

43509d8

Gemini authored: attempt to create a backwards compatible A2AClient a…

d057808

…nd A2AGrpcClient

gemini-code-assist bot reviewed Jul 30, 2025

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mikeas1 added 3 commits July 30, 2025 04:41

Restore some comments gemini mysteriously deleted

b32b0da

Fix an issue with ClientFactory not respecting transport URL, add tests

12e595d

Merge branch 'restful' into restful-2

e57c8f7

holtskinner changed the title ~~feat: Refactor client into BaseClient + ClientTransport~~ refactor: Refactor client into BaseClient + ClientTransport Jul 30, 2025

formatting

9182fdb

holtskinner reviewed Jul 30, 2025

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holtskinner approved these changes Jul 30, 2025

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mikeas1 added 2 commits July 30, 2025 15:46

Fix broken tests

ff0ad3b

Address issues in legacy client, review comments

22ef4db

mikeas1 marked this pull request as ready for review July 30, 2025 16:03

mikeas1 requested a review from a team as a code owner July 30, 2025 16:03

mikeas1 merged commit c2f4f2f into a2aproject:restful Jul 30, 2025
2 checks passed

holtskinner mentioned this pull request Jul 30, 2025

feat: Add RESTful API Serving #348

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refactor: Refactor client into BaseClient + ClientTransport #363

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