[bug]: Self_Payment Failed

[lukegao209]

Background

Alice(Tapd0.5) Bob(Tapd0.5)
Alice <----1 BTC Channel------>BOB
Alice <----100000 USDT Channel------>BOB

Self_Payment for USDT Channel:
1. Generate 100 USDT Invoice On Alice 
2. Pay invoice on Alice 
3. Success

Self_Payment for BTC Channel:
1. Generate 0.00001 BTC Invoice On Alice 
2. Pay invoice on Alice 
3. Failed

Logs ： logs.txt

I encountered an issue with allow_self_payment. When Alice and Bob have both a BTC-Channel and a TaprootAssets-Channel, creating a BTC invoice on Alice and performing a self-payment on Alice fails. Could this be a bug with self-payment when both Taproot channels and BTC channels coexist? (If a Taproot invoice is generated, self-payment works fine.) Here are the logs for reference.

It’s particularly worth noting whether there is a way to avoid using Taproot channels for small BTC invoices. This is important because using Taproot channels for such payments might result in insufficient local BTC balance in the Taproot channel, making it impossible to pay Taproot invoices.

[Roasbeef]

When Alice and Bob have both a BTC-Channel and a TaprootAssets-Channel, creating a BTC invoice on Alice and performing a self-payment on Alice fails

When you go to make the payment, you can specify the outgoing and incoming scid's.

[Roasbeef]

What's the purpose of the self payment here? Is it to rebalance, or implement user multi-plexing (accounts) over channels? If the latter why does a higher layer keeping track of balances not suffice?

It’s particularly worth noting whether there is a way to avoid using Taproot channels for small BTC invoices.

You can specify the outgoing scid here to avoid using certain channels for normal BTC invoices.