Feature Request: PSBT creation should include unspentTargetCount

unspentTargetCount Optional. When passed, the wallet will attempt to make sure the UTXO count of the wallet after this PSBT is signed and confirmed is equal to this number.

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The use case for this:

• In a wallet that periodically sends out transactions, keeping about 3-4 UTXOS in your wallet at all times makes it easy to ensure that one stuck transaction does not cause your wallet to choke up on the 25 unconfirmed tx chain limit… As it is unlikely that all 3 or all 4 of the “base” (confirmed) UTXOs will all accidentally be sent with low fees and get stuck.

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Implementation ideas:

• Simple: make this a “max” setting… then all you need to do is add some low value outpoints into the transaction as inputs to join everything together decreasing UTXO count to desired amount.
• Complex: Have min and max… is trickier, because if UTXO count is too low, you must maybe create multiple change outputs to increase UTXO count, which then brings up many extra questions about how to handle explicitChangeAddress etc. etc…

[NicolasDorier]

Very interesting. I need to think about how to do this, there is deep assumption in my transaction builder that there is only one change.

[NicolasDorier]

yes