Minor changes post review

Author: optout21

lightning/src/ln/channel.rs

@@ -2239,26 +2239,27 @@ impl<SP: Deref> PendingV2Channel<SP> where SP::Target: SignerProvider {
 	) -> Result<Option<InteractiveTxMessageSend>, APIError>
 	where ES::Target: EntropySource
 	{
-		let mut funding_inputs = self.dual_funding_context.our_funding_inputs.take().unwrap_or_else(|| vec![]);
+		let mut funding_inputs = Vec::new();
+		mem::swap(&mut self.dual_funding_context.our_funding_inputs, &mut funding_inputs);
 
 		if let Some(prev_funding_input) = prev_funding_input {
 			funding_inputs.push(prev_funding_input);
 		}
 
-		let mut funding_inputs_prev_outputs: Vec<TxOut> = Vec::with_capacity(funding_inputs.len());
+		let mut funding_inputs_prev_outputs: Vec<&TxOut> = Vec::with_capacity(funding_inputs.len());
 		// Check that vouts exist for each TxIn in provided transactions.
-		for (idx, input) in funding_inputs.iter().enumerate() {
-			if let Some(output) = input.1.as_transaction().output.get(input.0.previous_output.vout as usize) {
-				funding_inputs_prev_outputs.push(output.clone());
+		for (idx, (txin, tx)) in funding_inputs.iter().enumerate() {
+			if let Some(output) = tx.as_transaction().output.get(txin.previous_output.vout as usize) {
+				funding_inputs_prev_outputs.push(output);
 			} else {
 				return Err(APIError::APIMisuseError {
 					err: format!("Transaction with txid {} does not have an output with vout of {} corresponding to TxIn at funding_inputs[{}]",
-						input.1.as_transaction().compute_txid(), input.0.previous_output.vout, idx) });
+						tx.as_transaction().compute_txid(), txin.previous_output.vout, idx) });
 			}
 		}
 
 		let total_input_satoshis: u64 = funding_inputs.iter().map(
-			|input| input.1.as_transaction().output.get(input.0.previous_output.vout as usize).map(|out| out.value.to_sat()).unwrap_or(0)
+			|(txin, tx)| tx.as_transaction().output.get(txin.previous_output.vout as usize).map(|out| out.value.to_sat()).unwrap_or(0)
 		).sum();
 		if total_input_satoshis < self.dual_funding_context.our_funding_satoshis {
 			return Err(APIError::APIMisuseError {
@@ -2300,8 +2301,14 @@ impl<SP: Deref> PendingV2Channel<SP> where SP::Target: SignerProvider {
 				|err| APIError::APIMisuseError {
 					err: format!("Failed to get change script as new destination script, {:?}", err),
 				})?;
-			add_funding_change_output(change_value, change_script,
-				&mut funding_outputs, self.dual_funding_context.funding_feerate_sat_per_1000_weight);
+			let mut change_output = TxOut {
+				value: Amount::from_sat(change_value),
+				script_pubkey: change_script,
+			};
+			let change_output_weight = get_output_weight(&change_output.script_pubkey).to_wu();
+			let change_output_fee = fee_for_weight(self.dual_funding_context.funding_feerate_sat_per_1000_weight, change_output_weight);
+			change_output.value = Amount::from_sat(change_value.saturating_sub(change_output_fee));
+			funding_outputs.push(OutputOwned::Single(change_output));
 		}
 
 		let constructor_args = InteractiveTxConstructorArgs {
@@ -2320,7 +2327,7 @@ impl<SP: Deref> PendingV2Channel<SP> where SP::Target: SignerProvider {
 			.map_err(|_| APIError::APIMisuseError { err: "Incorrect shared output provided".into() })?;
 		let msg = tx_constructor.take_initiator_first_message();
 
-		self.interactive_tx_constructor.replace(tx_constructor);
+		self.interactive_tx_constructor = Some(tx_constructor);
 
 		Ok(msg)
 	}
@@ -5037,8 +5044,10 @@ pub(super) struct DualFundingChannelContext {
 	/// Note that the `our_funding_satoshis` field is equal to the total value of `our_funding_inputs`
 	/// minus any fees paid for our contributed weight. This means that change will never be generated
 	/// and the maximum value possible will go towards funding the channel.
+	///
+	/// Note that this field may be emptied once the interactive negotiation has been started.
 	#[allow(dead_code)] // TODO(dual_funding): Remove once contribution to V2 channels is enabled.
-	pub our_funding_inputs: Option<Vec<(TxIn, TransactionU16LenLimited)>>,
+	pub our_funding_inputs: Vec<(TxIn, TransactionU16LenLimited)>,
 }
 
 // Holder designates channel data owned for the benefit of the user client.
@@ -10029,7 +10038,7 @@ impl<SP: Deref> PendingV2Channel<SP> where SP::Target: SignerProvider {
 				their_funding_satoshis: None,
 				funding_tx_locktime,
 				funding_feerate_sat_per_1000_weight,
-				our_funding_inputs: Some(funding_inputs),
+				our_funding_inputs: funding_inputs,
 			},
 			interactive_tx_constructor: None,
 			interactive_tx_signing_session: None,
@@ -10175,7 +10184,7 @@ impl<SP: Deref> PendingV2Channel<SP> where SP::Target: SignerProvider {
 			their_funding_satoshis: Some(msg.common_fields.funding_satoshis),
 			funding_tx_locktime: LockTime::from_consensus(msg.locktime),
 			funding_feerate_sat_per_1000_weight: msg.funding_feerate_sat_per_1000_weight,
-			our_funding_inputs: Some(our_funding_inputs.clone()),
+			our_funding_inputs: our_funding_inputs.clone(),
 		};
 
 		let interactive_tx_constructor = Some(InteractiveTxConstructor::new(

lightning/src/ln/interactivetxs.rs

@@ -1670,7 +1670,7 @@ impl InteractiveTxConstructor {
 /// or None if a change is not needed/possible.
 #[allow(dead_code)] // TODO(dual_funding): Remove once begin_interactive_funding_tx_construction() is used
 pub(super) fn calculate_change_output_value(
-	is_initiator: bool, our_contribution: u64, funding_inputs_prev_outputs: &Vec<TxOut>,
+	is_initiator: bool, our_contribution: u64, funding_inputs_prev_outputs: &Vec<&TxOut>,
 	funding_outputs: &Vec<OutputOwned>, funding_feerate_sat_per_1000_weight: u32,
 	holder_dust_limit_satoshis: u64,
 ) -> Option<u64> {
@@ -2641,10 +2641,11 @@ mod tests {
 
 	#[test]
 	fn test_calculate_change_output_value_open() {
-		let input_prevouts = vec![
+		let input_prevouts_owned = vec![
 			TxOut { value: Amount::from_sat(70_000), script_pubkey: ScriptBuf::new() },
 			TxOut { value: Amount::from_sat(60_000), script_pubkey: ScriptBuf::new() },
 		];
+		let input_prevouts: Vec<&TxOut> = input_prevouts_owned.iter().collect();
 		let our_contributed = 110_000;
 		let txout = TxOut { value: Amount::from_sat(128_000), script_pubkey: ScriptBuf::new() };
 		let outputs = vec![OutputOwned::SharedControlFullyOwned(txout)];
@@ -2730,10 +2731,11 @@ mod tests {
 
 	#[test]
 	fn test_calculate_change_output_value_splice() {
-		let input_prevouts = vec![
+		let input_prevouts_owned = vec![
 			TxOut { value: Amount::from_sat(70_000), script_pubkey: ScriptBuf::new() },
 			TxOut { value: Amount::from_sat(60_000), script_pubkey: ScriptBuf::new() },
 		];
+		let input_prevouts: Vec<&TxOut> = input_prevouts_owned.iter().collect();
 		let our_contributed = 110_000;
 		let txout = TxOut { value: Amount::from_sat(148_000), script_pubkey: ScriptBuf::new() };
 		let outputs = vec![OutputOwned::Shared(SharedOwnedOutput::new(txout, our_contributed))];