Insert channel funding utxo before a splice-in

We insert a channel's funding utxo into our wallet so we can later
calculate the fees for the transaction, otherwise our wallet would have
incomplete information. We do it before the splice-in and not just on
the ChannelReady event to ensure better backwards compatibility.

Author: benthecarman

src/lib.rs

@@ -1319,6 +1319,15 @@ impl Node {
 				},
 			};
 
+			// insert channel's funding utxo into the wallet so we can later calculate fees
+			// correctly when viewing this splice-in.
+			self.wallet.insert_txo(funding_txo.into_bitcoin_outpoint(), funding_output).map_err(
+				|e| {
+					log_error!(self.logger, "Failed to splice channel: {:?}", e);
+					Error::ChannelSplicingFailed
+				},
+			)?;
+
 			self.channel_manager
 				.splice_channel(
 					&channel_details.channel_id,

src/wallet/mod.rs

@@ -26,7 +26,7 @@ use bitcoin::secp256k1::ecdh::SharedSecret;
 use bitcoin::secp256k1::ecdsa::{RecoverableSignature, Signature};
 use bitcoin::secp256k1::{All, PublicKey, Scalar, Secp256k1, SecretKey};
 use bitcoin::{
-	Address, Amount, FeeRate, ScriptBuf, Transaction, TxOut, Txid, WPubkeyHash, Weight,
+	Address, Amount, FeeRate, OutPoint, ScriptBuf, Transaction, TxOut, Txid, WPubkeyHash, Weight,
 	WitnessProgram, WitnessVersion,
 };
 use lightning::chain::chaininterface::BroadcasterInterface;
@@ -153,6 +153,19 @@ impl Wallet {
 		Ok(())
 	}
 
+	pub(crate) fn insert_txo(&self, outpoint: OutPoint, txout: TxOut) -> Result<(), Error> {
+		let mut locked_wallet = self.inner.lock().unwrap();
+		locked_wallet.insert_txout(outpoint, txout);
+
+		let mut locked_persister = self.persister.lock().unwrap();
+		locked_wallet.persist(&mut locked_persister).map_err(|e| {
+			log_error!(self.logger, "Failed to persist wallet: {}", e);
+			Error::PersistenceFailed
+		})?;
+
+		Ok(())
+	}
+
 	fn update_payment_store<'a>(
 		&self, locked_wallet: &'a mut PersistedWallet<KVStoreWalletPersister>,
 	) -> Result<(), Error> {