Add fee_paid_msat to PaymentSuccessful event

  The fee as returned from `PaymentSent` event generated by LDK and is
  saved in `PaymentSuccessful` event.

bindings/ldk_node.udl

@@ -154,7 +154,7 @@ enum BuildError {
 
 [Enum]
 interface Event {
-	PaymentSuccessful(PaymentHash payment_hash);
+	PaymentSuccessful(PaymentHash payment_hash, u64? fee_paid_msat);
 	PaymentFailed(PaymentHash payment_hash, PaymentFailureReason? reason);
 	PaymentReceived(PaymentHash payment_hash, u64 amount_msat);
 	ChannelPending(ChannelId channel_id, UserChannelId user_channel_id, ChannelId former_temporary_channel_id, PublicKey counterparty_node_id, OutPoint funding_txo);

src/event.rs

@@ -47,6 +47,8 @@ pub enum Event {
 	PaymentSuccessful {
 		/// The hash of the payment.
 		payment_hash: PaymentHash,
+		/// Paid fee in milli-satoshis.
+		fee_paid_msat: Option<u64>,
 	},
 	/// A sent payment has failed.
 	PaymentFailed {
@@ -106,6 +108,7 @@ pub enum Event {
 impl_writeable_tlv_based_enum!(Event,
 	(0, PaymentSuccessful) => {
 		(0, payment_hash, required),
+		(1, fee_paid_msat, option),
 	},
 	(1, PaymentFailed) => {
 		(0, payment_hash, required),
@@ -611,7 +614,7 @@ where
 					);
 				}
 				self.event_queue
-					.add_event(Event::PaymentSuccessful { payment_hash })
+					.add_event(Event::PaymentSuccessful { payment_hash, fee_paid_msat })
 					.unwrap_or_else(|e| {
 						log_error!(self.logger, "Failed to push to event queue: {}", e);
 						panic!("Failed to push to event queue");

tests/integration_tests_rust.rs

@@ -133,8 +133,28 @@ fn multi_hop_sending() {
 	let invoice = nodes[4].receive_payment(2_500_000, &"asdf", 9217).unwrap();
 	nodes[0].send_payment(&invoice).unwrap();
 
-	expect_event!(nodes[4], PaymentReceived);
-	expect_event!(nodes[0], PaymentSuccessful);
+	let payment_hash = match nodes[4].wait_next_event() {
+		ref e @ Event::PaymentReceived { payment_hash, amount_msat } => {
+			println!("{} got event {:?}", std::stringify!(node_b), e);
+			assert_eq!(amount_msat, 2_500_000);
+			nodes[4].event_handled();
+			payment_hash
+		},
+		ref e => {
+			panic!("{} got unexpected event!: {:?}", std::stringify!(node_b), e);
+		},
+	};
+	match nodes[0].wait_next_event() {
+		ref e @ Event::PaymentSuccessful { payment_hash: hash, fee_paid_msat } => {
+			println!("{} got event {:?}", std::stringify!(node_b), e);
+			assert_eq!(hash, payment_hash);
+			assert_eq!(fee_paid_msat, Some(2000));
+			nodes[0].event_handled();
+		},
+		ref e => {
+			panic!("{} got unexpected event!: {:?}", std::stringify!(node_b), e);
+		},
+	};
 }
 
 #[test]