Implement custom debug for PathBuildingHop

Add other fields to log for PathBuildingHop

Author: jurvis

lightning/src/routing/router.rs

@@ -423,8 +423,8 @@ impl<'a> CandidateRouteHop<'a> {
 /// so that we can choose cheaper paths (as per Dijkstra's algorithm).
 /// Fee values should be updated only in the context of the whole path, see update_value_and_recompute_fees.
 /// These fee values are useful to choose hops as we traverse the graph "payee-to-payer".
-#[derive(Clone, Debug)]
-struct PathBuildingHop<'a> {
+#[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,
@@ -463,6 +463,13 @@ struct PathBuildingHop<'a> {
 	value_contribution_msat: u64,
 }
 
+impl<'a> core::fmt::Debug for PathBuildingHop<'a> {
+	fn fmt(&self, f: &mut core::fmt::Formatter) -> Result<(), core::fmt::Error> {
+        write!(f, "PathBuildingHop: node_id: {:?}, short_channel_id: {}, fee_msat: {}, path_penalty_msat: {}, path_htlc_minimum_msat: {}, cltv_expiry_delta: {}", self.node_id, self.candidate.short_channel_id(), self.fee_msat, self.path_penalty_msat, self.path_htlc_minimum_msat, self.candidate.cltv_expiry_delta())?;
+		Ok(())
+    }
+}
+
 // Instantiated with a list of hops with correct data in them collected during path finding,
 // an instance of this struct should be further modified only via given methods.
 #[derive(Clone)]
@@ -1299,7 +1306,7 @@ where L::Target: Logger {
 				ordered_hops.last_mut().unwrap().0.fee_msat = value_contribution_msat;
 				ordered_hops.last_mut().unwrap().0.hop_use_fee_msat = 0;
 
-				log_trace!(logger, "Found a path back to us from the target with {} hops contributing up to {} msat: {:?}",
+				log_trace!(logger, "Found a path back to us from the target with {} hops contributing up to {} msat: \n{:?}",
 					ordered_hops.len(), value_contribution_msat, ordered_hops);
 
 				let mut payment_path = PaymentPath {hops: ordered_hops};