Issue: Function signature injection of config is causing issues.

[victor-ab]

Issue you'd like to raise.

How to replicate it:

from typing import Dict
from langsmith import traceable

from fastapi import FastAPI
from langsmith.middleware import TracingMiddleware

app = FastAPI()

app.add_middleware(TracingMiddleware)


@app.post("/health")
@traceable()
async def ping(input_string: str) -> Dict[str, str]:
    return {"pong": input_string}

Logs:

INFO:     127.0.0.1:32942 - "GET /openapi.json HTTP/1.1" 200 OK
Failed to get inputs for (input_string: str) -> Dict[str, str]: got an unexpected keyword argument 'config'

The issue is here in python/langsmith/run_helpers.py#L762:

        if not sig.parameters.get("config"):
            sig = sig.replace(
                parameters=[
                    *(
                        param
                        for param in sig.parameters.values()
                        if param.kind != inspect.Parameter.VAR_KEYWORD
                    ),
                    inspect.Parameter(
                        "config", inspect.Parameter.KEYWORD_ONLY, default=None
                    ),
                    *(
                        param
                        for param in sig.parameters.values()
                        if param.kind == inspect.Parameter.VAR_KEYWORD
                    ),
                ]
            )
            selected_wrapper.__signature__ = sig  # type: ignore[attr-defined]
        return selected_wrapper

Not sure how this is being used, but looking at the traces, it seems to be passing a None to it.

Suggestion:

No response