BIP 125 selection for replacement

[monokh]

Replace by fee BIP125 states that at least one input in the transaction needs to be reused in the replacing transaction. Is this something this library should cater for? Such that you also provide the inputs from the previous transaction and the coin selection will ensure that at least one of them is used.

Alternatively are there any workarounds for using this library for RBF transactions?

[monokh]

I found that I could use coinselect/accumulative pretty reliably to achieve this if I prioritised the utxos spent in the previous transaction before sending to 'coinselect'. However there probably should be something to 100% guarantee that those prioritised inputs aren't skipped.

[spencerstock]

Agree that this should be prioritized. I wrote something to accomplish this in Coinbase Wallet's codebase. If you only use accumulative for the original and for the replacement it should work 100% of the time already, as long as you guarantee the inputs are the same when both transactions are generated.