CIP30: getUtxos null instead of undefined

[SebastienGllmt]

Currently CIP30 defines the getUtxos endpoint should return undefined if the requested amount can't be satisfied

The problem is that browser message passing uses JSON and undefined is not valid JSON. This can easily introduce subtle bugs (some libraries silently convert undefined to null) and it's needless complexity when we could just define the spec to return null instead.

Strictly speaking this is a breaking change, but I'm not sure if it will affect app at the moment.

Another option would be to return an error instead of null which I think also makes sense

[alessandrokonrad]

I'm not even sure if undefined or null make even sense here, because the return type is TransactionUnspentOutput[]. If no utxos were found by filtering by certain assets, it should return an empty array imo.

[SebastienGllmt]

It's not filtering by an asset -- it's filtering by an amount

Honestly though I think taking in an argument list for everything in CIP30 was a mistake. We should have made function only have a single parameter -- a JS object. It would have make backward/forward compatibility much easier -- especially for functions like this where people may want to add different filters, etc. in the future but can't anymore because of the optional parameter

[alessandrokonrad]

It's not filtering by an asset -- it's filtering by an amount

Yeah, but as you say it's filtering, so normally when I apply a filter on an array I always get back an array again regardless of the result.

[SebastienGllmt]

Returning an empty array would only make sense if this was element-wise filtering though. Otherwise you wouldn't be able to differentiate between a wallet with no UTXOs and a wallet with UTXOs but just not enough to sum to the value you requested

[mkazlauskas]

Returning an empty array would only make sense if this was element-wise filtering though. Otherwise you wouldn't be able to differentiate between a wallet with no UTXOs and a wallet with UTXOs but just not enough to sum to the value you requested

Agree. I'm wondering what is the intended use case for this filtering. If it's for input selection then this interface is not sufficient and should be redesigned in my opinion (see this comment).