Rename method, review

Author: optout21

lightning/src/ln/channel.rs

@@ -30,7 +30,7 @@ use crate::ln::types::ChannelId;
 use crate::types::payment::{PaymentPreimage, PaymentHash};
 use crate::types::features::{ChannelTypeFeatures, InitFeatures};
 use crate::ln::interactivetxs::{
-	get_output_weight, need_to_add_funding_change_output, HandleTxCompleteValue, HandleTxCompleteResult, InteractiveTxConstructor,
+	get_output_weight, calculate_change_output_value, HandleTxCompleteValue, HandleTxCompleteResult, InteractiveTxConstructor,
 	InteractiveTxConstructorArgs, InteractiveTxMessageSend, InteractiveTxSigningSession, InteractiveTxMessageSendResult,
 	OutputOwned, SharedOwnedOutput, TX_COMMON_FIELDS_WEIGHT,
 };
@@ -2298,7 +2298,7 @@ impl<SP: Deref> PendingV2Channel<SP> where SP::Target: SignerProvider {
 		};
 
 		// Optionally add change output
-		if let Some(change_value) = need_to_add_funding_change_output(
+		if let Some(change_value) = calculate_change_output_value(
 			self.funding.is_outbound(), self.dual_funding_context.our_funding_satoshis,
 			&funding_inputs_prev_outputs, &funding_outputs,
 			self.dual_funding_context.funding_feerate_sat_per_1000_weight,
@@ -2308,8 +2308,8 @@ impl<SP: Deref> PendingV2Channel<SP> where SP::Target: SignerProvider {
 				|err| APIError::APIMisuseError {
 					err: format!("Failed to get change script as new destination script, {:?}", err),
 				})?;
-			let _res = add_funding_change_output(
-				change_value, change_script, &mut funding_outputs, self.dual_funding_context.funding_feerate_sat_per_1000_weight);
+			add_funding_change_output(change_value, change_script,
+				&mut funding_outputs, self.dual_funding_context.funding_feerate_sat_per_1000_weight);
 		}
 
 		let constructor_args = InteractiveTxConstructorArgs {
@@ -4871,7 +4871,7 @@ pub(super) fn check_v2_funding_inputs_sufficient(
 fn add_funding_change_output(
 	change_value: u64, change_script: ScriptBuf,
 	funding_outputs: &mut Vec<OutputOwned>, funding_feerate_sat_per_1000_weight: u32,
-) -> TxOut {
+) {
 	let mut change_output = TxOut {
 		value: Amount::from_sat(change_value),
 		script_pubkey: change_script,
@@ -4880,7 +4880,6 @@ fn add_funding_change_output(
 	let change_output_fee = fee_for_weight(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.clone()));
-	change_output
 }
 
 /// Context for dual-funded channels.

lightning/src/ln/interactivetxs.rs

@@ -1667,8 +1667,10 @@ impl InteractiveTxConstructor {
 /// Determine whether a change output should be added or not, and if so, of what size,
 /// considering our given inputs, outputs, and intended contribution.
 /// Computes and takes into account fees.
+/// Return value is the value computed for the change output (in satoshis),
+/// 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 need_to_add_funding_change_output(
+pub(super) fn calculate_change_output_value(
 	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,
@@ -1709,7 +1711,7 @@ mod tests {
 	use crate::chain::chaininterface::{fee_for_weight, FEERATE_FLOOR_SATS_PER_KW};
 	use crate::ln::channel::TOTAL_BITCOIN_SUPPLY_SATOSHIS;
 	use crate::ln::interactivetxs::{
-		generate_holder_serial_id, need_to_add_funding_change_output, AbortReason,
+		calculate_change_output_value, generate_holder_serial_id, AbortReason,
 		HandleTxCompleteValue, InteractiveTxConstructor, InteractiveTxConstructorArgs,
 		InteractiveTxMessageSend, MAX_INPUTS_OUTPUTS_COUNT, MAX_RECEIVED_TX_ADD_INPUT_COUNT,
 		MAX_RECEIVED_TX_ADD_OUTPUT_COUNT,
@@ -2639,7 +2641,7 @@ mod tests {
 	}
 
 	#[test]
-	fn test_need_to_add_funding_change_output_open() {
+	fn test_calculate_change_output_value_open() {
 		let input_prevouts = vec![
 			TxOut { value: Amount::from_sat(70_000), script_pubkey: ScriptBuf::new() },
 			TxOut { value: Amount::from_sat(60_000), script_pubkey: ScriptBuf::new() },
@@ -2655,7 +2657,7 @@ mod tests {
 		let common_fees = 126;
 		{
 			// There is leftover for change
-			let res = need_to_add_funding_change_output(
+			let res = calculate_change_output_value(
 				true,
 				our_contributed,
 				&input_prevouts,
@@ -2667,7 +2669,7 @@ mod tests {
 		}
 		{
 			// There is leftover for change, without common fees
-			let res = need_to_add_funding_change_output(
+			let res = calculate_change_output_value(
 				false,
 				our_contributed,
 				&input_prevouts,
@@ -2679,7 +2681,7 @@ mod tests {
 		}
 		{
 			// Larger fee, smaller change
-			let res = need_to_add_funding_change_output(
+			let res = calculate_change_output_value(
 				true,
 				our_contributed,
 				&input_prevouts,
@@ -2691,7 +2693,7 @@ mod tests {
 		}
 		{
 			// Insufficient inputs, no leftover
-			let res = need_to_add_funding_change_output(
+			let res = calculate_change_output_value(
 				false,
 				130_000,
 				&input_prevouts,
@@ -2703,7 +2705,7 @@ mod tests {
 		}
 		{
 			// Very small leftover
-			let res = need_to_add_funding_change_output(
+			let res = calculate_change_output_value(
 				false,
 				128_100,
 				&input_prevouts,
@@ -2715,7 +2717,7 @@ mod tests {
 		}
 		{
 			// Small leftover, but not dust
-			let res = need_to_add_funding_change_output(
+			let res = calculate_change_output_value(
 				false,
 				128_100,
 				&input_prevouts,
@@ -2728,7 +2730,7 @@ mod tests {
 	}
 
 	#[test]
-	fn test_need_to_add_funding_change_output_splice() {
+	fn test_calculate_change_output_value_splice() {
 		let input_prevouts = vec![
 			TxOut { value: Amount::from_sat(70_000), script_pubkey: ScriptBuf::new() },
 			TxOut { value: Amount::from_sat(60_000), script_pubkey: ScriptBuf::new() },
@@ -2744,7 +2746,7 @@ mod tests {
 		let common_fees = 126;
 		{
 			// There is leftover for change
-			let res = need_to_add_funding_change_output(
+			let res = calculate_change_output_value(
 				true,
 				our_contributed,
 				&input_prevouts,
@@ -2756,7 +2758,7 @@ mod tests {
 		}
 		{
 			// Very small leftover
-			let res = need_to_add_funding_change_output(
+			let res = calculate_change_output_value(
 				false,
 				128_100,
 				&input_prevouts,
@@ -2768,7 +2770,7 @@ mod tests {
 		}
 		{
 			// Small leftover, but not dust
-			let res = need_to_add_funding_change_output(
+			let res = calculate_change_output_value(
 				false,
 				128_100,
 				&input_prevouts,