fix(interop/langchain): use arun for async langchain tools#2806
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fix(interop/langchain): use arun for async langchain tools#2806obchain wants to merge 2 commits into
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LangChainInteroperability.convert_tool always wrapped the langchain tool with the sync run() dispatcher, even when the tool defined a native async implementation. Inside an asyncio event loop (e.g. a_initiate_chat), this blocks on the synchronous path and degrades concurrency. Detect tools that provide a native coroutine — StructuredTool with `coroutine=...` or BaseTool subclasses that override `_arun` — and wrap those with an async function that awaits `langchain_tool.arun(...)`. Sync tools keep the existing sync wrapper for backward compatibility, and the behavior for tools whose async impl is just a thread-pool fallback of `_run` is left unchanged. Add regression tests covering both StructuredTool(coroutine=...) and class-based BaseTool subclasses with overridden _arun. Fixes ag2ai#1402
Replace the if/else `def func` shadowing pattern with two distinct helpers (`async_func`, `sync_func`) assigned to a single `func` variable of type `Callable[..., Any]`. Drops the 'All conditional function variants must have identical signatures' mypy [misc] error and removes the no-any-unimported error by widening `_has_async_run`'s parameter annotation to `Any` (it already guards on isinstance internally).
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Why are these changes needed?
LangChainInteroperability.convert_toolalways wrapped the langchain tool with the synchronousrun()dispatcher, even when the tool defined a native async implementation. Calling such a converted tool inside an asyncio event loop (e.g.a_initiate_chat) blocks on the sync path and defeats the point of using an async langchain tool — exactly the behaviour reported in #1402.Fix
Detect tools that provide a native coroutine and switch to an async wrapper that awaits
langchain_tool.arun(...):StructuredTool(created via@langchain_core.tools.toolon anasync def) — detected viacoroutine is not None.BaseToolsubclasses that override_arun— detected by comparingtype(t)._arunagainstBaseTool._arun.Tools without a native async implementation keep the existing synchronous wrapper — converting them to async would only wrap
_runin a thread executor, which would be a behaviour change with no benefit for existing sync-only callers.Tests
TestLangChainInteroperabilityAsync—StructuredTool(coroutine=...)path: wrapper is a coroutine function and runs througharun.TestLangChainInteroperabilityClassBasedAsync—BaseToolsubclass with overridden_arun: same checks. The class's_runraisesNotImplementedErrorso any accidental fallback to the sync dispatcher would surface as a test failure.TestLangChainInteroperability,TestLangChainInteroperabilityWithoutPydanticInput) continue to pass — the sync wrapper is preserved when no native coroutine is detected.uv run pytest test/interop/langchain/test_langchain.py -vv→ 8 passed, 2 skipped (OpenAI-credential gated).Related issue number
Fixes #1402
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