Passing negative amount to splice_init fails with unrecognized option

[Sjors]

Running v23.08 with experimental_splicing on Ubuntu 23.04, GNU bash, version 5.2.15.

Trying to splice in a positive amount "works" as expected:

lightning-cli splice_init ... 1sat
{
   "code": 354,
   "message": "splicing not supported"
}

Trying to splice out a negative amount doesn't:

lightning-cli splice_init ... -1sat
lightning-cli: -1sat: unrecognized option

I also tried \-1sat and "1sat".

It does seem to work with -k:

lightning-cli splice_init -k channel_id=... amount=-1sat
{
   "code": 354,
   "message": "splicing not supported"
}

Maybe it's easier to just have splice_in_init and splice_out_init with only positive amounts? The rest of the RPCs would stay unchanged.

[ddustin]

The thinking was since you can only splice whole sat amounts and building signed the input types to use raw numbers was less effort / complication (sats / msats types do not allow negative values) , using raw signed values would work well for this. But perhaps that's worth reconsidering if it's breaking users' expectations.

[ddustin]

There was an issue where negative values (ie -100) would be interpreted as a command named "100".

PR #6675 now special cases "-" followed by a digit as a numerical value instead of an unrecognized command.

[ddustin]

Adding the -- technique usage example to the splice_init documentation in PR #6677.