* fix(mcp): implement sync invocation wrapper for async MCP tools
Since DeerFlowClient streams synchronously, invoking async-only MCP tools
(loaded via langchain-mcp-adapters) resulted in a NotImplementedError.
This commit bridges the sync/async gap by dynamically injecting a `func`
wrapper into `StructuredTool` instances that only have a `coroutine`.
Key changes:
- Added `sync_wrapper` in `get_mcp_tools` to execute async tool calls.
- Handled nested event loops by delegating to a global `ThreadPoolExecutor`
when an event loop is already running, avoiding `RuntimeError`.
- Added detailed error logging within the wrapper for better transparency.
- Added comprehensive test coverage in `test_mcp_sync_wrapper.py` verifying
tool patching, event loop behavior, and exception propagation.
* refactor(mcp): extract sync wrapper to module level and fix test mocks
Addressed PR review comments:
- Extracted _make_sync_tool_wrapper to module level to avoid nested func definitions.
- Refactored tests to use the actual production helper instead of duplicating logic.
- Fixed AsyncMock patching for awaited dependencies in tests.
- Added atexit hook for graceful thread pool shutdown.
- Fixed PEP8 blank line formatting in tests.
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Co-authored-by: Willem Jiang <willem.jiang@gmail.com>
