Allow submitting form without adding a message in useChat hook

[lesleh]

Currently we do nothing if no text is input in the form - https://github.com/vercel-labs/ai/blob/fd69e9a5628d1cd21a7c4a36584b4c577e0cc0a6/packages/core/react/use-chat.ts#L253

But, submitting a new API request without adding a new user message is a good way to get the LLM to continue its previous response, for example if the user hit stop, or the previous response reached the token limit. This is how the OpenAI playground works.

[MaxLeiter]

Can you use reload? https://sdk.vercel.ai/docs/api-reference/use-chat

[lesleh]

@MaxLeiter unfortunately not, reload works differently. Instead of adding another assistant response, it removes the last assistant response and requests a new one. So you couldn't use it to make the hook request another assistant message without providing an additional user message.

[shuding]

I think you can call append manually with role set to 'assistant'?

[lesleh]

@shuding I don't believe so, append looks like it's more for adding a message with content you already have, not asking for a new message to be generated.

[shuding]

It seems like we need a new option in reload to explicitly send a request without removing the last assistant response. For example reload({ removeLastAssistantMessage: true }). Need a better name though.

[pomber]

It seems like we need a new option in reload to explicitly send a request without removing the last assistant response. For example reload({ removeLastAssistantMessage: true }). Need a better name though.

Maybe even more flexibility? reload(messages => transformTheMessagesBeforeSendingThem(messages))

I need this so I can modify the last user message before reloading.

[shuding]

Love the idea from @pomber, vote for this:

reload({
  transform: (messages) => newMessages
})

So we can have other options added in the future. PR welcome!

[prashantbhudwal]

@shuding Raised PR. #989

#989