AssistantStream.accumulateDelta does not cover accumulating toolCall

[romdotdog]

Confirm this is a Node library issue and not an underlying OpenAI API issue

• This is an issue with the Node library

Describe the bug

Say we have a delta like

{"delta":{"step_details":{"type":"tool_calls","tool_calls":[{"index":0,"type":"function","function":{"arguments":"{}"}}]}}}

You're missing functionality here:

https://github.com/openai/openai-node/blob/116e38aae33a2d7b88c27d783a95b41e56500600/src/lib/AssistantStream.ts#L686C1-L691C8

I recommend adding something like

} else if (
    Array.isArray(accValue) &&
    Array.isArray(deltaValue)
) {
    if (
        accValue.every(
            x => typeof x === "string" || typeof x === "number"
        )
    ) {
        accValue.push(...deltaValue); // Use spread syntax for efficient addition
        continue;
    // new code below
    } else if (
        deltaValue.every(
            x =>
                isObj(x) &&
                x.hasOwnProperty("index") &&
                typeof x.index === "number"
        )
    ) {
        for (let i = 0; i < deltaValue.length; i++) {
            const index = deltaValue[i].index;
            accValue[index] = this.accumulateDelta(
                accValue[index],
                deltaValue[i]
            );
        }
        continue;
    }
    // end of new code
}

To Reproduce

Any streamed tool call with arguments will do. Notice how the argument field is empty in the toolCall parameter from the event "toolCallDone"

Code snippets

No response

OS

Linux

Node version

Node v20.11.1

Library version

openai v4.34.0