remove node_id from PathBuildingHop

  use `CandidateRouteHop::target` function instead of `node_id`

Author: jbesraa

lightning/src/routing/router.rs

@@ -1252,9 +1252,6 @@ fn iter_equal<I1: Iterator, I2: Iterator>(mut iter_a: I1, mut iter_b: I2)
 /// These fee values are useful to choose hops as we traverse the graph "payee-to-payer".
 #[derive(Clone)]
 pub struct PathBuildingHop<'a> {
-	// Note that this should be dropped in favor of loading it from CandidateRouteHop, but doing so
-	// is a larger refactor and will require careful performance analysis.
-	node_id: NodeId,
 	candidate: CandidateRouteHop<'a>,
 	fee_msat: u64,
 
@@ -1292,7 +1289,7 @@ impl<'a> core::fmt::Debug for PathBuildingHop<'a> {
 	fn fmt(&self, f: &mut core::fmt::Formatter) -> Result<(), core::fmt::Error> {
 		let mut debug_struct = f.debug_struct("PathBuildingHop");
 		debug_struct
-			.field("node_id", &self.node_id)
+			.field("node_id", &self.candidate.target())
 			.field("short_channel_id", &self.candidate.short_channel_id())
 			.field("total_fee_msat", &self.total_fee_msat)
 			.field("next_hops_fee_msat", &self.next_hops_fee_msat)
@@ -1945,7 +1942,6 @@ where L::Target: Logger {
 							// This will affect our decision on selecting short_channel_id
 							// as a way to reach the $dest_node_id.
 							PathBuildingHop {
-								node_id: $dest_node_id.clone(),
 								candidate: $candidate.clone(),
 								fee_msat: 0,
 								next_hops_fee_msat: u64::max_value(),
@@ -2035,7 +2031,6 @@ where L::Target: Logger {
 									old_entry.next_hops_fee_msat = $next_hops_fee_msat;
 									old_entry.hop_use_fee_msat = hop_use_fee_msat;
 									old_entry.total_fee_msat = total_fee_msat;
-									old_entry.node_id = $dest_node_id.clone();
 									old_entry.candidate = $candidate.clone();
 									old_entry.fee_msat = 0; // This value will be later filled with hop_use_fee_msat of the following channel
 									old_entry.path_htlc_minimum_msat = path_htlc_minimum_msat;
@@ -2405,7 +2400,7 @@ where L::Target: Logger {
 
 				'path_walk: loop {
 					let mut features_set = false;
-					if let Some(first_channels) = first_hop_targets.get(&ordered_hops.last().unwrap().0.node_id) {
+					if let Some(first_channels) = first_hop_targets.get(&ordered_hops.last().unwrap().0.candidate.target()) {
 						for details in first_channels {
 							if let Some(scid) = ordered_hops.last().unwrap().0.candidate.short_channel_id() {
 								if details.get_outbound_payment_scid().unwrap() == scid {
@@ -2417,7 +2412,7 @@ where L::Target: Logger {
 						}
 					}
 					if !features_set {
-						if let Some(node) = network_nodes.get(&ordered_hops.last().unwrap().0.node_id) {
+						if let Some(node) = network_nodes.get(&ordered_hops.last().unwrap().0.candidate.target()) {
 							if let Some(node_info) = node.announcement_info.as_ref() {
 								ordered_hops.last_mut().unwrap().1 = node_info.features.clone();
 							} else {
@@ -2434,11 +2429,11 @@ where L::Target: Logger {
 					// save this path for the payment route. Also, update the liquidity
 					// remaining on the used hops, so that we take them into account
 					// while looking for more paths.
-					if ordered_hops.last().unwrap().0.node_id == maybe_dummy_payee_node_id {
+					if ordered_hops.last().unwrap().0.candidate.target() == maybe_dummy_payee_node_id {
 						break 'path_walk;
 					}
 
-					new_entry = match dist.remove(&ordered_hops.last().unwrap().0.node_id) {
+					new_entry = match dist.remove(&ordered_hops.last().unwrap().0.candidate.target()) {
 						Some(payment_hop) => payment_hop,
 						// We can't arrive at None because, if we ever add an entry to targets,
 						// we also fill in the entry in dist (see add_entry!).
@@ -2477,12 +2472,13 @@ where L::Target: Logger {
 				// Remember that we used these channels so that we don't rely
 				// on the same liquidity in future paths.
 				let mut prevented_redundant_path_selection = false;
-				let prev_hop_iter = core::iter::once(&our_node_id)
-					.chain(payment_path.hops.iter().map(|(hop, _)| &hop.node_id));
+				let prev_hop_iter = core::iter::once(our_node_id)
+					.chain(payment_path.hops.iter().map(|(hop, _)| hop.candidate.target()));
 				for (prev_hop, (hop, _)) in prev_hop_iter.zip(payment_path.hops.iter()) {
+					let target = hop.candidate.target();
 					let spent_on_hop_msat = value_contribution_msat + hop.next_hops_fee_msat;
 					let used_liquidity_msat = used_liquidities
-						.entry(hop.candidate.id(*prev_hop < hop.node_id))
+						.entry(hop.candidate.id(prev_hop < target))
 						.and_modify(|used_liquidity_msat| *used_liquidity_msat += spent_on_hop_msat)
 						.or_insert(spent_on_hop_msat);
 					let hop_capacity = hop.candidate.effective_capacity();
@@ -2657,8 +2653,8 @@ where L::Target: Logger {
 	});
 	for idx in 0..(selected_route.len() - 1) {
 		if idx + 1 >= selected_route.len() { break; }
-		if iter_equal(selected_route[idx    ].hops.iter().map(|h| (h.0.candidate.id(true), h.0.node_id)),
-		              selected_route[idx + 1].hops.iter().map(|h| (h.0.candidate.id(true), h.0.node_id))) {
+		if iter_equal(selected_route[idx    ].hops.iter().map(|h| (h.0.candidate.id(true), h.0.candidate.target())),
+		              selected_route[idx + 1].hops.iter().map(|h| (h.0.candidate.id(true), h.0.candidate.target()))) {
 			let new_value = selected_route[idx].get_value_msat() + selected_route[idx + 1].get_value_msat();
 			selected_route[idx].update_value_and_recompute_fees(new_value);
 			selected_route.remove(idx + 1);
@@ -2683,14 +2679,14 @@ where L::Target: Logger {
 				// there are announced channels between the endpoints. If so, the hop might be
 				// referring to any of the announced channels, as its `short_channel_id` might be
 				// an alias, in which case we don't take any chances here.
-				network_graph.node(&hop.node_id).map_or(false, |hop_node|
+				network_graph.node(&hop.candidate.target()).map_or(false, |hop_node|
 					hop_node.channels.iter().any(|scid| network_graph.channel(*scid)
 							.map_or(false, |c| c.as_directed_from(&prev_hop_node_id).is_some()))
 				)
 			};
 
 			hops.push(RouteHop {
-				pubkey: PublicKey::from_slice(hop.node_id.as_slice()).map_err(|_| LightningError{err: format!("Public key {:?} is invalid", &hop.node_id), action: ErrorAction::IgnoreAndLog(Level::Trace)})?,
+				pubkey: PublicKey::from_slice(hop.candidate.target().as_slice()).map_err(|_| LightningError{err: format!("Public key {:?} is invalid", &hop.candidate.target()), action: ErrorAction::IgnoreAndLog(Level::Trace)})?,
 				node_features: node_features.clone(),
 				short_channel_id: hop.candidate.short_channel_id().unwrap(),
 				channel_features: hop.candidate.features(),
@@ -2699,7 +2695,7 @@ where L::Target: Logger {
 				maybe_announced_channel,
 			});
 
-			prev_hop_node_id = hop.node_id;
+			prev_hop_node_id = hop.candidate.target();
 		}
 		let mut final_cltv_delta = final_cltv_expiry_delta;
 		let blinded_tail = payment_path.hops.last().and_then(|(h, _)| {