Minor renames, two tests

Author: optout21

lightning/src/ln/channel.rs

@@ -4252,12 +4252,14 @@ fn get_v2_channel_reserve_satoshis(channel_value_satoshis: u64, dust_limit_satos
 	cmp::min(channel_value_satoshis, cmp::max(q, dust_limit_satoshis))
 }
 
+/// Determine whether with our given inputs, outputs, and intended contribution
+/// a change output should be added or not, and if so, of waht size
 #[allow(dead_code)] // TODO(dual_funding): Remove once begin_interactive_funding_tx_construction() is used
 fn need_to_add_funding_change_output(is_initiator: bool,
-	our_funding_satoshis: u64, funding_inputs_prev_outputs: &Vec<TxOut>,
-	funding_outputs: &Vec<OutputOwned>, funding_feerate_sat_per_1000_weight: u32,
-	holder_dust_limit_satoshis: u64,
-) -> Result<Option<u64>, ChannelError> {
+	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> {
 	let our_funding_inputs_weight = funding_inputs_prev_outputs.iter().fold(0u64, |weight, prev_output| {
 		weight.saturating_add(estimate_input_weight(prev_output).to_wu())
 	});
@@ -4276,13 +4278,13 @@ fn need_to_add_funding_change_output(is_initiator: bool,
 	let total_input_satoshis: u64 = funding_inputs_prev_outputs.iter().map(|out| out.value.to_sat()).sum();
 
 	let remaining_value = total_input_satoshis
-		.saturating_sub(our_funding_satoshis)
+		.saturating_sub(our_contribution)
 		.saturating_sub(fees_sats);
 
-	if remaining_value < holder_dust_limit_satoshis {
-		Ok(None)
+	if remaining_value <= holder_dust_limit_satoshis {
+		None
 	} else {
-		Ok(Some(remaining_value))
+		Some(remaining_value)
 	}
 }
 
@@ -4295,7 +4297,7 @@ fn maybe_add_funding_change_output<SP: Deref>(signer_provider: &SP, is_initiator
 	let remaining_value = match need_to_add_funding_change_output(
 		is_initiator, our_funding_satoshis, funding_inputs_prev_outputs,
 		funding_outputs, funding_feerate_sat_per_1000_weight, holder_dust_limit_satoshis
-	)? {
+	) {
 		None => {
 			// No need to add
 			return Ok(None);
@@ -12094,44 +12096,81 @@ mod tests {
 	}
 
 	#[test]
-	fn test_need_to_add_funding_change_output() {
-		let prevouts = vec![
+	fn test_need_to_add_funding_change_output_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()},
 		];
-		let txout = TxOut { value: Amount::from_sat(125_000), script_pubkey: ScriptBuf::new()};
-		let outputs = vec![OutputOwned::Shared(SharedOwnedOutput::new(txout, 105_000))];
 		let our_contributed = 110_000;
+		let txout = TxOut { value: Amount::from_sat(128_000), script_pubkey: ScriptBuf::new()};
+		let outputs = vec![OutputOwned::SharedControlFullyOwned(txout)];
 		let funding_feerate_sat_per_1000_weight = 3000;
 
-		let total_inputs: u64 = prevouts.iter().map(|o| o.value.to_sat()).sum();
+		let total_inputs: u64 = input_prevouts.iter().map(|o| o.value.to_sat()).sum();
 		let gross_change = total_inputs - our_contributed;
 		let fees = 1746;
 		let common_fees = 126;
 		{
 			// There is leftover for change
-			let res = need_to_add_funding_change_output(true, our_contributed, &prevouts, &outputs, funding_feerate_sat_per_1000_weight, 300); 
-			assert_eq!(res.unwrap().unwrap(), gross_change - fees - common_fees);
+			let res = need_to_add_funding_change_output(true, our_contributed, &input_prevouts, &outputs, funding_feerate_sat_per_1000_weight, 300);
+			assert_eq!(res.unwrap(), gross_change - fees - common_fees);
 		}
 		{
 			// There is leftover for change, without common fees
-			let res = need_to_add_funding_change_output(false, our_contributed, &prevouts, &outputs, funding_feerate_sat_per_1000_weight, 300); 
-			assert_eq!(res.unwrap().unwrap(), gross_change - fees);
+			let res = need_to_add_funding_change_output(false, our_contributed, &input_prevouts, &outputs, funding_feerate_sat_per_1000_weight, 300);
+			assert_eq!(res.unwrap(), gross_change - fees);
+		}
+		{
+			// Larger fee, smaller change
+			let res = need_to_add_funding_change_output(true, our_contributed, &input_prevouts, &outputs, 9000, 300);
+			assert_eq!(res.unwrap(), 14384);
 		}
 		{
 			// Insufficient inputs, no leftover
-			let res = need_to_add_funding_change_output(false, 130_000, &prevouts, &outputs, funding_feerate_sat_per_1000_weight, 300); 
-			assert!(res.unwrap().is_none());
+			let res = need_to_add_funding_change_output(false, 130_000, &input_prevouts, &outputs, funding_feerate_sat_per_1000_weight, 300);
+			assert!(res.is_none());
+		}
+		{
+			// Very small leftover
+			let res = need_to_add_funding_change_output(false, 128_100, &input_prevouts, &outputs, funding_feerate_sat_per_1000_weight, 300);
+			assert!(res.is_none());
+		}
+		{
+			// Small leftover, but not dust
+			let res = need_to_add_funding_change_output(false, 128_100, &input_prevouts, &outputs, funding_feerate_sat_per_1000_weight, 100);
+			assert_eq!(res.unwrap(), 154);
+		}
+	}
+
+	#[test]
+	fn test_need_to_add_funding_change_output_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()},
+		];
+		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))];
+		let funding_feerate_sat_per_1000_weight = 3000;
+
+		let total_inputs: u64 = input_prevouts.iter().map(|o| o.value.to_sat()).sum();
+		let gross_change = total_inputs - our_contributed;
+		let fees = 1746;
+		let common_fees = 126;
+		{
+			// There is leftover for change
+			let res = need_to_add_funding_change_output(true, our_contributed, &input_prevouts, &outputs, funding_feerate_sat_per_1000_weight, 300);
+			assert_eq!(res.unwrap(), gross_change - fees - common_fees);
 		}
 		{
 			// Very small leftover
-			let res = need_to_add_funding_change_output(false, 128_100, &prevouts, &outputs, funding_feerate_sat_per_1000_weight, 300); 
-			assert!(res.unwrap().is_none());
+			let res = need_to_add_funding_change_output(false, 128_100, &input_prevouts, &outputs, funding_feerate_sat_per_1000_weight, 300);
+			assert!(res.is_none());
 		}
 		{
 			// Small leftover, but not dust
-			let res = need_to_add_funding_change_output(false, 128_100, &prevouts, &outputs, funding_feerate_sat_per_1000_weight, 100); 
-			assert_eq!(res.unwrap().unwrap(), 154);
+			let res = need_to_add_funding_change_output(false, 128_100, &input_prevouts, &outputs, funding_feerate_sat_per_1000_weight, 100);
+			assert_eq!(res.unwrap(), 154);
 		}
 	}
 }