[Feat Request] Add AIStreamCallbacksAndOptions for simple text stream response.

[arnab710]

Feature Description

Also for simple text stream responses (via toTextStreamResponse() or other methods), we should be able to use AIStreamCallbacksAndOptions (onStart, onToken, onFinish, etc.).

Use Case

Raw stream data protocol has been changed in version 3.1 or later.
I upgraded to version 3.1 and StreamingTextResponse stopped streaming simple text responses. The new format is now -> 0: "Je", 0: " suis", 0: "des".
However, this method does support AIStreamCallbacksAndOptions.

const result = await streamText({
        model: openAi(model, {
            user: user.uid,
        }),
        messages,
    });
    
    const stream = result.toAIStream({
        async onStart() {
            console.debug('start streaming..');
            do_something();
        },
        onToken(token) {
            console.debug('Token received', token);
        },
        onCompletion: async (completion) => {
            console.debug('onCompletion called', completion);
        },
        async onFinal(completion) {
            console.debug('ending stream..');
            do_something();
        },
    });

    return new StreamingTextResponse(stream);

So, for simple text responses, I found the method toTextStreamResponse.

const result = await streamText({
        model: openAi(model, {
            user: user.uid,
        }),
        messages,
    });

    result.toTextStreamResponse();

But, afaik it doesn't support AIStreamCallbacksAndOptions, which I require in my case. Specifically, I would like to know exactly when the stream processing starts (i.e., the onStart use case).

(note: I have a Chrome extension, useChat or useCompletion can't be used. I implemented an HTTP streaming response handler for streaming in the extension.)

Additional context

...

[lgrammel]

This is not possible for a text stream. By definition, it only transmits text chunks. If you want to use more complex objects, please use the AIStream instead.