Remove path_id from Responder, and OnionMessageResponse struct

1. The path_id will be removed from the codebase in the following
   commits.

Author: shaavan

fuzz/src/onion_message.rs

@@ -346,9 +346,9 @@ mod tests {
 						"Received an onion message with path_id None and a reply_path: Custom(TestCustomMessage)"
 						.to_string())), Some(&1));
 			assert_eq!(log_entries.get(&("lightning::onion_message::messenger".to_string(),
-						"Constructing onion message when responding with Custom Message to an onion message with path_id None: TestCustomMessage".to_string())), Some(&1));
+						"Constructing onion message when responding with Custom Message to an onion message: TestCustomMessage".to_string())), Some(&1));
 			assert_eq!(log_entries.get(&("lightning::onion_message::messenger".to_string(),
-						"Buffered onion message when responding with Custom Message to an onion message with path_id None".to_string())), Some(&1));
+						"Buffered onion message when responding with Custom Message to an onion message".to_string())), Some(&1));
 		}
 
 		let two_unblinded_hops_om = "\

lightning/src/onion_message/functional_tests.rs

@@ -427,14 +427,13 @@ fn async_response_over_one_blinded_hop() {
 
 	// 2. Define the message sent from Bob to Alice.
 	let message = TestCustomMessage::Ping;
-	let path_id = Some([2; 32]);
 
 	// 3. Simulate the creation of a Blinded Reply path provided by Bob.
 	let secp_ctx = Secp256k1::new();
 	let reply_path = BlindedPath::new_for_message(&[], nodes[1].node_id, &*nodes[1].entropy_source, &secp_ctx).unwrap();
 
 	// 4. Create a responder using the reply path for Alice.
-	let responder = Some(Responder::new(reply_path, path_id));
+	let responder = Some(Responder::new(reply_path));
 
 	// 5. Expect Alice to receive the message and create a response instruction for it.
 	alice.custom_message_handler.expect_message(message.clone());
@@ -466,11 +465,10 @@ fn async_response_with_reply_path_succeeds() {
 
 	// Alice receives a message from Bob with an added reply_path for responding back.
 	let message = TestCustomMessage::Ping;
-	let path_id = Some([2; 32]);
 	let reply_path = BlindedPath::new_for_message(&[], bob.node_id, &*bob.entropy_source, &secp_ctx).unwrap();
 
 	// Alice asynchronously responds to Bob, expecting a response back from him.
-	let responder = Responder::new(reply_path, path_id);
+	let responder = Responder::new(reply_path);
 	alice.custom_message_handler.expect_message_and_response(message.clone());
 	let response_instruction = alice.custom_message_handler.handle_custom_message(message, Some(responder));
 
@@ -503,13 +501,12 @@ fn async_response_with_reply_path_fails() {
 
 	// Alice receives a message from Bob with an added reply_path for responding back.
 	let message = TestCustomMessage::Ping;
-	let path_id = Some([2; 32]);
 	let reply_path = BlindedPath::new_for_message(&[], bob.node_id, &*bob.entropy_source, &secp_ctx).unwrap();
 
 	// Alice tries to asynchronously respond to Bob, but fails because the nodes are unannounced and
 	// disconnected. Thus, a reply path could no be created for the response.
 	disconnect_peers(alice, bob);
-	let responder = Responder::new(reply_path, path_id);
+	let responder = Responder::new(reply_path);
 	alice.custom_message_handler.expect_message_and_response(message.clone());
 	let response_instruction = alice.custom_message_handler.handle_custom_message(message, Some(responder));
 

lightning/src/onion_message/messenger.rs

@@ -344,20 +344,17 @@ impl OnionMessageRecipient {
 pub struct Responder {
 	/// The path along which a response can be sent.
 	reply_path: BlindedPath,
-	path_id: Option<[u8; 32]>
 }
 
 impl_writeable_tlv_based!(Responder, {
 	(0, reply_path, required),
-	(2, path_id, option),
 });
 
 impl Responder {
 	/// Creates a new [`Responder`] instance with the provided reply path.
-	pub(super) fn new(reply_path: BlindedPath, path_id: Option<[u8; 32]>) -> Self {
+	pub(super) fn new(reply_path: BlindedPath) -> Self {
 		Responder {
 			reply_path,
-			path_id,
 		}
 	}
 
@@ -368,7 +365,6 @@ impl Responder {
 		ResponseInstruction::WithoutReplyPath(OnionMessageResponse {
 			message: response,
 			reply_path: self.reply_path,
-			path_id: self.path_id,
 		})
 	}
 
@@ -379,7 +375,6 @@ impl Responder {
 		ResponseInstruction::WithReplyPath(OnionMessageResponse {
 			message: response,
 			reply_path: self.reply_path,
-			path_id: self.path_id,
 		})
 	}
 }
@@ -388,7 +383,6 @@ impl Responder {
 pub struct OnionMessageResponse<T: OnionMessageContents> {
 	message: T,
 	reply_path: BlindedPath,
-	path_id: Option<[u8; 32]>,
 }
 
 /// `ResponseInstruction` represents instructions for responding to received messages.
@@ -1272,9 +1266,8 @@ where
 				Err(err) => {
 					log_trace!(
 						self.logger,
-						"Failed to create reply path when responding with {} to an onion message \
-						with path_id {:02x?}: {:?}",
-						message_type, response.path_id, err
+						"Failed to create reply path when responding with {} to an onion message: {:?}",
+						message_type, err
 					);
 					return Err(err);
 				}
@@ -1284,9 +1277,8 @@ where
 		self.find_path_and_enqueue_onion_message(
 			response.message, Destination::BlindedPath(response.reply_path), reply_path,
 			format_args!(
-				"when responding with {} to an onion message with path_id {:02x?}",
+				"when responding with {} to an onion message",
 				message_type,
-				response.path_id
 			)
 		).map(|result| Some(result))
 	}
@@ -1446,9 +1438,7 @@ where
 					"Received an onion message with path_id {:02x?} and {} reply_path: {:?}",
 					path_id, if reply_path.is_some() { "a" } else { "no" }, message);
 
-				let responder = reply_path.map(
-					|reply_path| Responder::new(reply_path, path_id)
-				);
+				let responder = reply_path.map(Responder::new);
 				match message {
 					ParsedOnionMessageContents::Offers(msg) => {
 						let response_instructions = self.offers_handler.handle_message(msg, responder);