fix(payment): skip store insertion on routing failures to allow retry

Adjust the error handling for outbound payments so that when a payment
fails at the pathfinding stage (e.g., `RetryableSendFailure::RouteNotFound`),
we bypass inserting a `PaymentStatus::Failed` entry into the database.

Fix #903

Author: alexgrad42

src/payment/bolt11.rs

@@ -307,6 +307,7 @@ impl Bolt11Payment {
 				log_error!(self.logger, "Failed to send payment: {:?}", e);
 				match e {
 					RetryableSendFailure::DuplicatePayment => Err(Error::DuplicatePayment),
+					RetryableSendFailure::RouteNotFound => Err(Error::PaymentSendingFailed),
 					_ => {
 						let kind = PaymentKind::Bolt11 {
 							hash: payment_hash,
@@ -422,6 +423,7 @@ impl Bolt11Payment {
 				log_error!(self.logger, "Failed to send payment: {:?}", e);
 				match e {
 					RetryableSendFailure::DuplicatePayment => Err(Error::DuplicatePayment),
+					RetryableSendFailure::RouteNotFound => Err(Error::PaymentSendingFailed),
 					_ => {
 						let kind = PaymentKind::Bolt11 {
 							hash: payment_hash,

src/payment/spontaneous.rs

@@ -139,6 +139,7 @@ impl SpontaneousPayment {
 
 				match e {
 					RetryableSendFailure::DuplicatePayment => Err(Error::DuplicatePayment),
+					RetryableSendFailure::RouteNotFound => Err(Error::PaymentSendingFailed),
 					_ => {
 						let kind = PaymentKind::Spontaneous {
 							hash: payment_hash,

tests/integration_tests_rust.rs

@@ -2957,3 +2957,34 @@ async fn splice_in_with_all_balance() {
 	node_a.stop().unwrap();
 	node_b.stop().unwrap();
 }
+
+#[tokio::test(flavor = "multi_thread", worker_threads = 1)]
+async fn test_retry_on_routing_failure() {
+	let (bitcoind, electrsd) = setup_bitcoind_and_electrsd();
+	let chain_source = random_chain_source(&bitcoind, &electrsd);
+	let (node_a, node_b) = setup_two_nodes(&chain_source, false, true, true);
+
+	let invoice = node_b
+		.bolt11_payment()
+		.receive(
+			100_000,
+			&Bolt11InvoiceDescription::Direct(Description::new("test-retry".to_string()).unwrap()),
+			3600,
+		)
+		.unwrap();
+
+	let first_attempt = node_a.bolt11_payment().send(&invoice, None);
+	assert!(first_attempt.is_err(), "expecting error at first attempt");
+	assert_eq!(first_attempt.unwrap_err(), NodeError::PaymentSendingFailed);
+
+	let second_attempt = node_a.bolt11_payment().send(&invoice, None);
+
+	assert_ne!(
+		second_attempt.unwrap_err(),
+		NodeError::DuplicatePayment,
+		"The invoice hash was incorrectly locked in the payment store after a routing failure!"
+	);
+
+	node_a.stop().unwrap();
+	node_b.stop().unwrap();
+}