add the bolt12 invoice to the PaymentSend event

To enable proof of payment, we need to share the bolt12 invoice with the library user.

This is already possible if we `manually_handle_bolt12_invoices`, but
this approach requires a significant amount of work from the user.

This commit adds the bolt12 invoice to the PaymentSend event when
the payment is completed. This allows the user to always have the option to
perform proof of payment.

Link: #3344
Signed-off-by: Vincenzo Palazzo <vincenzopalazzodev@gmail.com>

Author: vincenzopalazzo

lightning/src/events/mod.rs

@@ -939,6 +939,8 @@ pub enum Event {
 		///
 		/// [`Route::get_total_fees`]: crate::routing::router::Route::get_total_fees
 		fee_paid_msat: Option<u64>,
+		/// The bolt12 invoice that was paid. `None` if the payment was a non-bolt12 payment.
+		bolt12_invoice: Option<Bolt12Invoice>,
 	},
 	/// Indicates an outbound payment failed. Individual [`Event::PaymentPathFailed`] events
 	/// provide failure information for each path attempt in the payment, including retries.
@@ -1190,12 +1192,12 @@ pub enum Event {
 		/// events generated or serialized by versions prior to 0.0.122.
 		next_user_channel_id: Option<u128>,
 		/// The node id of the previous node.
-		/// 
+		///
 		/// This is only `None` for HTLCs received prior to 0.1 or for events serialized by
 		/// versions prior to 0.1
 		prev_node_id: Option<PublicKey>,
 		/// The node id of the next node.
-		/// 
+		///
 		/// This is only `None` for HTLCs received prior to 0.1 or for events serialized by
 		/// versions prior to 0.1
 		next_node_id: Option<PublicKey>,
@@ -1546,13 +1548,14 @@ impl Writeable for Event {
 					(13, payment_id, option),
 				});
 			},
-			&Event::PaymentSent { ref payment_id, ref payment_preimage, ref payment_hash, ref fee_paid_msat } => {
+			&Event::PaymentSent { ref payment_id, ref payment_preimage, ref payment_hash, ref fee_paid_msat, ref bolt12_invoice } => {
 				2u8.write(writer)?;
 				write_tlv_fields!(writer, {
 					(0, payment_preimage, required),
 					(1, payment_hash, required),
 					(3, payment_id, option),
 					(5, fee_paid_msat, option),
+					(7, bolt12_invoice, option),
 				});
 			},
 			&Event::PaymentPathFailed {
@@ -1886,11 +1889,13 @@ impl MaybeReadable for Event {
 					let mut payment_hash = None;
 					let mut payment_id = None;
 					let mut fee_paid_msat = None;
+					let mut bolt12_invoice = None;
 					read_tlv_fields!(reader, {
 						(0, payment_preimage, required),
 						(1, payment_hash, option),
 						(3, payment_id, option),
 						(5, fee_paid_msat, option),
+						(7, bolt12_invoice, option),
 					});
 					if payment_hash.is_none() {
 						payment_hash = Some(PaymentHash(Sha256::hash(&payment_preimage.0[..]).to_byte_array()));
@@ -1900,6 +1905,7 @@ impl MaybeReadable for Event {
 						payment_preimage,
 						payment_hash: payment_hash.unwrap(),
 						fee_paid_msat,
+						bolt12_invoice,
 					}))
 				};
 				f()

lightning/src/ln/offers_tests.rs

@@ -2406,3 +2406,51 @@ fn no_double_pay_with_stale_channelmanager() {
 	assert!(nodes[0].node.get_and_clear_pending_events().is_empty());
 }
 
+/// Checks that an invoice for a refund without any blinded paths can be requested and that we have
+/// at the end all the information for make a Proof of Payment.
+#[test]
+fn pays_for_offer_for_pop() {
+	let chanmon_cfgs = create_chanmon_cfgs(2);
+	let node_cfgs = create_node_cfgs(2, &chanmon_cfgs);
+	let node_chanmgrs = create_node_chanmgrs(2, &node_cfgs, &[None, None]);
+	let nodes = create_network(2, &node_cfgs, &node_chanmgrs);
+	create_announced_chan_between_nodes_with_value(&nodes, 0, 1, 10_000_000, 1_000_000_000);
+	let alice = &nodes[0];
+	let alice_id = alice.node.get_our_node_id();
+	let bob = &nodes[1];
+	let bob_id = bob.node.get_our_node_id();
+	let offer = alice.node
+		.create_offer_builder(None).unwrap()
+		.clear_paths()
+		.amount_msats(10_000_000)
+		.build().unwrap();
+	assert_eq!(offer.issuer_signing_pubkey(), Some(alice_id));
+	assert!(offer.paths().is_empty());
+
+	let payment_id = PaymentId([1; 32]);
+	bob.node.pay_for_offer(&offer, None, None, None, payment_id, Retry::Attempts(0), None).unwrap();
+	expect_recent_payment!(bob, RecentPaymentDetails::AwaitingInvoice, payment_id);
+	let onion_message = bob.onion_messenger.next_onion_message_for_peer(alice_id).unwrap();
+	alice.onion_messenger.handle_onion_message(bob_id, &onion_message);
+	let (invoice_request, _) = extract_invoice_request(alice, &onion_message);
+	let payment_context = PaymentContext::Bolt12Offer(Bolt12OfferContext {
+		offer_id: offer.id(),
+		invoice_request: InvoiceRequestFields {
+			payer_signing_pubkey: invoice_request.payer_signing_pubkey(),
+			quantity: None,
+			payer_note_truncated: None,
+			human_readable_name: None,
+		},
+	});
+
+	let onion_message = alice.onion_messenger.next_onion_message_for_peer(bob_id).unwrap();
+	bob.onion_messenger.handle_onion_message(alice_id, &onion_message);
+	let (invoice, _) = extract_invoice(bob, &onion_message);
+	route_bolt12_payment(bob, &[alice], &invoice);
+	expect_recent_payment!(bob, RecentPaymentDetails::Pending, payment_id);
+
+	// FIXME(vincenzopalazzo): The following call will read the PaymentSend (in paricular the expect_payment_sent), so we should have a
+	// better way to check the event. Or just pass down the invoice and assert inside it.
+	claim_bolt12_payment(bob, &[alice], payment_context);
+	expect_recent_payment!(bob, RecentPaymentDetails::Fulfilled, payment_id);
+}

lightning/src/ln/outbound_payment.rs

@@ -1947,6 +1947,7 @@ impl OutboundPayments {
 					payment_preimage,
 					payment_hash,
 					fee_paid_msat,
+					bolt12_invoice: payment.get().bolt12_invoice().cloned(),
 				}, Some(ev_completion_action.clone())));
 				payment.get_mut().mark_fulfilled();
 			}