Allow multiline prompts

[rasbt]

This workaround let's users submit multiline prompts. Either via copy & paste or by typing on the command line and using Enter once to start a new line. If the newline is blank and a user hits Enter again, it submits the prompt.

If a user only wants to submit a single line prompt, pressing Enter twice might be extra effort, but I think it's worth it given that users can now use multiline prompts without "bugs".

We can also explore other options based on external libraries some time later but I think it's kind of useful to fix this so users can use CodeGemma etc.

Fixes #1275

[rasbt]

I was spending way too much time on this, but yeah, there is no nice way to do that. For some reason it's not easy to reliably log CTRL+Enter info. You could use the keyboard library but that might be too intrusive because it monitors key board inputs and I think may not work on systems with limited user rights.

Maybe the best solution is to just have a special keyword to stop parsing.

The way I updated it is that if you enter :submit: on a new line, it will submit the prompt. From using this a bit, it is cumbersome to type a special word instead of just pressing enter or CTRL+Enter. n

Not sure how to move forward with this. What do you think here @carmocca and @awaelchli , should we just leave it as is, use :submit: (or something similar), or perhaps something else?

[awaelchli]

I'm good with whatever the solution if it does not impact the single-line user experience.

However, keep in mind that if you add special syntax for the multi-line input, it won't solve your original issue #1275 where you copy-pasted multi-line into the terminal.

[rasbt]

Ok, thinking about this more, I think there is no one-size-fits-all approach.

So, I changed it back so that by default nothing changes.

But you can now additionally pass the --multiline_prompts arg:

litgpt chat \
   --checkpoint_dir checkpoints/microsoft/phi-2 \
   --multiline_prompts True

to work with multiline prompts. This will then require users to enter !submit to submit. (I found that :submit: is just too annoying to type on US keyboards.)

This should also address #1275 based on trying it.

The code should be ready for review @carmocca and @awaelchli .

[carmocca]

Some tests are failing

[rasbt]

All the feedback should be addressed now. Thanks @carmocca @awaelchli for keeping the bar high!

The default usage is the same as before, except that you can now exit via !exit and !quit in addition to 'Enter' on a blank line:

⚡ multiline ~/litgpt litgpt chat --checkpoint_dir checkpoints/microsoft/phi-2
Now chatting with phi-2.
To exit, press 'Enter' on an empty prompt.

Seed set to 1234
>> Prompt: what do llamas eat/
>> Reply:  Llamas eat grass, shrubs, and leaves.

Time for inference: 0.74 sec total, 17.47 tokens/sec, 13 tokens

>> Prompt: !exit
⚡ multiline ~/litgpt 

And with --multiline true, you exit via !exit and !submit as well:

>> Prompt: (Type '!submit' on a new line to end input).
!exit
⚡ multiline ~/litgpt litgpt chat --checkpoint_dir checkpoints/microsoft/phi-2 --multiline true
Now chatting with phi-2.
To exit, enter '!quit' or '!exit' on an empty prompt and press 'Enter'.

Seed set to 1234
>> Prompt: (Type '!submit' on a new line to end input).
Hi
I have a question:
What do Llamas eat?
!submit
>> Reply:  llamas eat grass and hay.

Time for inference: 0.75 sec total, 10.64 tokens/sec, 8 tokens

>> Prompt: (Type '!submit' on a new line to end input).
!exit