[langchain] WandbTracer incompatible with langchain V2 Tracer API about wandb HOT 6 OPEN

Hi @MarkAWard . Thanks for raising this issue. I was able to reproduce this issue and am working on a fix. I will update here soon.

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Hey, @MarkAWard: This PR should fix the serialization issue with the new RunV2 API. Can you please let me know if your use-case works as expected when run from the branch? I'll tag one of the LangChain maintainers once you confirm. - All unittests pass as of now in LangChain

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Thanks @parambharat my use-case did work using your branch. With the change we did lose the model_dict that was previously passed to the WandbTraceTree, it's not as important to me as having the traces/spans working properly but did want to note that.

Would you be open to injecting the serializer as an optional dependency to the WandbTracer? Currently it just uses _serialize_io, but it would be nice to be able to extend or replace the serializer. For example in my branch I had added a condition to serialize pydantic objects:

def _serialize_io(run_inputs: Optional[dict]) -> dict:
    ...
        elif isinstance(value, (BaseModel, PydanticBaseModel)):
            serialized_inputs[key] = (
                value.model_dump_json()
                if hasattr(value, "model_dump_json")
                else value.json()
            )
    ...

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Thank you so much for reporting this, @MarkAWard, and thank you so much for looking into it so fast, @parambharat! Tracking this thread from the wandb support's side as well.

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Hi @MarkAWard,

With the change we did lose the model_dict that was previously passed to the WandbTraceTree, it's not as important to me as having the traces/spans working properly but did want to note that.

Thanks for pointing out the missing model_dict. I have pushed new changes to re-add the model architecture to the trace logging. You should now also see the Model Architecture tab in the logged traces.

Would you be open to injecting the serializer as an optional dependency to the WandbTracer?

I've added a new argument io_serializer to the WandTracer that allows you to pass a custom serializer. I've also included PydanticBaseModels in the serializer's defaults alongside the exisiting protobufs.

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