OpenAI Adapter Chunk response missing handling for tool_calls

Checked other resources

[X] I added a very descriptive title to this issue.
[X] I searched the LangChain documentation with the integrated search.
[X] I used the GitHub search to find a similar question and didn't find it.
[X] I am sure that this is a bug in LangChain rather than my code.
[X] The bug is not resolved by updating to the latest stable version of LangChain (or the specific integration package).

Example Code

In the following code, there is no support for tool_calls args in langchain_community.adapters -> openai

def _convert_message_chunk(chunk: BaseMessageChunk, i: int) -> dict:
    _dict: Dict[str, Any] = {}
    if isinstance(chunk, AIMessageChunk):
        if i == 0:
            # Only shows up in the first chunk
            _dict["role"] = "assistant"
        if "function_call" in chunk.additional_kwargs:
            _dict["function_call"] = chunk.additional_kwargs["function_call"]
            # If the first chunk is a function call, the content is not empty string,
            # not missing, but None.
            if i == 0:
                _dict["content"] = None
        else:
            _dict["content"] = chunk.content
    else:
        raise ValueError(f"Got unexpected streaming chunk type: {type(chunk)}")
    # This only happens at the end of streams, and OpenAI returns as empty dict
    if _dict == {"content": ""}:
        _dict = {}
    return _dict

Error Message and Stack Trace (if applicable)

No response

Description

I am trying to create OpenAI compatible endpoints using Langchain. Langchain community project provides openai adapter but it is missing handling for tool_calls in the streaming workflow.

System Info

langchain==0.2.6 langchain-anthropic==0.1.19 langchain-aws==0.1.10 langchain-community==0.2.6 langchain-core==0.2.15 langchain-experimental==0.0.63 langchain-openai==0.1.15 langchain-text-splitters==0.2.2 openinference-instrumentation-langchain==0.1.20

langchain-ai / langchain