Extract watch_channel_internal/update_channel_internal from Watch impl

Pure refactor: move the bodies of Watch::watch_channel and
Watch::update_channel into pub(crate) methods on ChainMonitor, and have
the Watch trait methods delegate to them. This prepares for adding
deferred mode where the Watch methods will conditionally queue
operations instead of executing them immediately.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: joostjager

lightning/src/chain/chainmonitor.rs

@@ -1058,6 +1058,160 @@ where
 
 		Ok(ChannelMonitorUpdateStatus::Completed)
 	}
+
+	fn watch_channel_internal(
+		&self, channel_id: ChannelId, monitor: ChannelMonitor<ChannelSigner>,
+	) -> Result<ChannelMonitorUpdateStatus, ()> {
+		let logger = WithChannelMonitor::from(&self.logger, &monitor, None);
+		let mut monitors = self.monitors.write().unwrap();
+		let entry = match monitors.entry(channel_id) {
+			hash_map::Entry::Occupied(_) => {
+				log_error!(logger, "Failed to add new channel data: channel monitor for given channel ID is already present");
+				return Err(());
+			},
+			hash_map::Entry::Vacant(e) => e,
+		};
+		log_trace!(logger, "Got new ChannelMonitor");
+		let update_id = monitor.get_latest_update_id();
+		let mut pending_monitor_updates = Vec::new();
+		let persist_res = self.persister.persist_new_channel(monitor.persistence_key(), &monitor);
+		match persist_res {
+			ChannelMonitorUpdateStatus::InProgress => {
+				log_info!(logger, "Persistence of new ChannelMonitor in progress",);
+				pending_monitor_updates.push(update_id);
+			},
+			ChannelMonitorUpdateStatus::Completed => {
+				log_info!(logger, "Persistence of new ChannelMonitor completed",);
+			},
+			ChannelMonitorUpdateStatus::UnrecoverableError => {
+				let err_str = "ChannelMonitor[Update] persistence failed unrecoverably. This indicates we cannot continue normal operation and must shut down.";
+				log_error!(logger, "{}", err_str);
+				panic!("{}", err_str);
+			},
+		}
+		if let Some(ref chain_source) = self.chain_source {
+			monitor.load_outputs_to_watch(chain_source, &self.logger);
+		}
+		entry.insert(MonitorHolder {
+			monitor,
+			pending_monitor_updates: Mutex::new(pending_monitor_updates),
+		});
+		Ok(persist_res)
+	}
+
+	fn update_channel_internal(
+		&self, channel_id: ChannelId, update: &ChannelMonitorUpdate,
+	) -> ChannelMonitorUpdateStatus {
+		// `ChannelMonitorUpdate`'s `channel_id` is `None` prior to 0.0.121 and all channels in those
+		// versions are V1-established. For 0.0.121+ the `channel_id` fields is always `Some`.
+		debug_assert_eq!(update.channel_id.unwrap(), channel_id);
+		// Update the monitor that watches the channel referred to by the given outpoint.
+		let monitors = self.monitors.read().unwrap();
+		match monitors.get(&channel_id) {
+			None => {
+				let logger = WithContext::from(&self.logger, None, Some(channel_id), None);
+				log_error!(logger, "Failed to update channel monitor: no such monitor registered");
+
+				// We should never ever trigger this from within ChannelManager. Technically a
+				// user could use this object with some proxying in between which makes this
+				// possible, but in tests and fuzzing, this should be a panic.
+				#[cfg(debug_assertions)]
+				panic!("ChannelManager generated a channel update for a channel that was not yet registered!");
+				#[cfg(not(debug_assertions))]
+				ChannelMonitorUpdateStatus::InProgress
+			},
+			Some(monitor_state) => {
+				let monitor = &monitor_state.monitor;
+				let logger = WithChannelMonitor::from(&self.logger, &monitor, None);
+				log_trace!(logger, "Updating ChannelMonitor to id {}", update.update_id,);
+
+				// We hold a `pending_monitor_updates` lock through `update_monitor` to ensure we
+				// have well-ordered updates from the users' point of view. See the
+				// `pending_monitor_updates` docs for more.
+				let mut pending_monitor_updates =
+					monitor_state.pending_monitor_updates.lock().unwrap();
+				let update_res = monitor.update_monitor(
+					update,
+					&self.broadcaster,
+					&self.fee_estimator,
+					&self.logger,
+				);
+
+				let update_id = update.update_id;
+				let persist_res = if update_res.is_err() {
+					// Even if updating the monitor returns an error, the monitor's state will
+					// still be changed. Therefore, we should persist the updated monitor despite the error.
+					// We don't want to persist a `monitor_update` which results in a failure to apply later
+					// while reading `channel_monitor` with updates from storage. Instead, we should persist
+					// the entire `channel_monitor` here.
+					log_warn!(logger, "Failed to update ChannelMonitor. Going ahead and persisting the entire ChannelMonitor");
+					self.persister.update_persisted_channel(
+						monitor.persistence_key(),
+						None,
+						monitor,
+					)
+				} else {
+					self.persister.update_persisted_channel(
+						monitor.persistence_key(),
+						Some(update),
+						monitor,
+					)
+				};
+				match persist_res {
+					ChannelMonitorUpdateStatus::InProgress => {
+						pending_monitor_updates.push(update_id);
+						log_debug!(
+							logger,
+							"Persistence of ChannelMonitorUpdate id {:?} in progress",
+							update_id,
+						);
+					},
+					ChannelMonitorUpdateStatus::Completed => {
+						log_debug!(
+							logger,
+							"Persistence of ChannelMonitorUpdate id {:?} completed",
+							update_id,
+						);
+					},
+					ChannelMonitorUpdateStatus::UnrecoverableError => {
+						// Take the monitors lock for writing so that we poison it and any future
+						// operations going forward fail immediately.
+						core::mem::drop(pending_monitor_updates);
+						core::mem::drop(monitors);
+						let _poison = self.monitors.write().unwrap();
+						let err_str = "ChannelMonitor[Update] persistence failed unrecoverably. This indicates we cannot continue normal operation and must shut down.";
+						log_error!(logger, "{}", err_str);
+						panic!("{}", err_str);
+					},
+				}
+
+				// We may need to start monitoring for any alternative funding transactions.
+				if let Some(ref chain_source) = self.chain_source {
+					for (funding_outpoint, funding_script) in
+						update.internal_renegotiated_funding_data()
+					{
+						log_trace!(
+							logger,
+							"Registering renegotiated funding outpoint {} with the filter to monitor confirmations and spends",
+							funding_outpoint
+						);
+						chain_source.register_tx(&funding_outpoint.txid, &funding_script);
+						chain_source.register_output(WatchedOutput {
+							block_hash: None,
+							outpoint: funding_outpoint,
+							script_pubkey: funding_script,
+						});
+					}
+				}
+
+				if update_res.is_err() {
+					ChannelMonitorUpdateStatus::InProgress
+				} else {
+					persist_res
+				}
+			},
+		}
+	}
 }
 
 impl<
@@ -1272,155 +1426,13 @@ where
 	fn watch_channel(
 		&self, channel_id: ChannelId, monitor: ChannelMonitor<ChannelSigner>,
 	) -> Result<ChannelMonitorUpdateStatus, ()> {
-		let logger = WithChannelMonitor::from(&self.logger, &monitor, None);
-		let mut monitors = self.monitors.write().unwrap();
-		let entry = match monitors.entry(channel_id) {
-			hash_map::Entry::Occupied(_) => {
-				log_error!(logger, "Failed to add new channel data: channel monitor for given channel ID is already present");
-				return Err(());
-			},
-			hash_map::Entry::Vacant(e) => e,
-		};
-		log_trace!(logger, "Got new ChannelMonitor");
-		let update_id = monitor.get_latest_update_id();
-		let mut pending_monitor_updates = Vec::new();
-		let persist_res = self.persister.persist_new_channel(monitor.persistence_key(), &monitor);
-		match persist_res {
-			ChannelMonitorUpdateStatus::InProgress => {
-				log_info!(logger, "Persistence of new ChannelMonitor in progress",);
-				pending_monitor_updates.push(update_id);
-			},
-			ChannelMonitorUpdateStatus::Completed => {
-				log_info!(logger, "Persistence of new ChannelMonitor completed",);
-			},
-			ChannelMonitorUpdateStatus::UnrecoverableError => {
-				let err_str = "ChannelMonitor[Update] persistence failed unrecoverably. This indicates we cannot continue normal operation and must shut down.";
-				log_error!(logger, "{}", err_str);
-				panic!("{}", err_str);
-			},
-		}
-		if let Some(ref chain_source) = self.chain_source {
-			monitor.load_outputs_to_watch(chain_source, &self.logger);
-		}
-		entry.insert(MonitorHolder {
-			monitor,
-			pending_monitor_updates: Mutex::new(pending_monitor_updates),
-		});
-		Ok(persist_res)
+		self.watch_channel_internal(channel_id, monitor)
 	}
 
 	fn update_channel(
 		&self, channel_id: ChannelId, update: &ChannelMonitorUpdate,
 	) -> ChannelMonitorUpdateStatus {
-		// `ChannelMonitorUpdate`'s `channel_id` is `None` prior to 0.0.121 and all channels in those
-		// versions are V1-established. For 0.0.121+ the `channel_id` fields is always `Some`.
-		debug_assert_eq!(update.channel_id.unwrap(), channel_id);
-		// Update the monitor that watches the channel referred to by the given outpoint.
-		let monitors = self.monitors.read().unwrap();
-		match monitors.get(&channel_id) {
-			None => {
-				let logger = WithContext::from(&self.logger, None, Some(channel_id), None);
-				log_error!(logger, "Failed to update channel monitor: no such monitor registered");
-
-				// We should never ever trigger this from within ChannelManager. Technically a
-				// user could use this object with some proxying in between which makes this
-				// possible, but in tests and fuzzing, this should be a panic.
-				#[cfg(debug_assertions)]
-				panic!("ChannelManager generated a channel update for a channel that was not yet registered!");
-				#[cfg(not(debug_assertions))]
-				ChannelMonitorUpdateStatus::InProgress
-			},
-			Some(monitor_state) => {
-				let monitor = &monitor_state.monitor;
-				let logger = WithChannelMonitor::from(&self.logger, &monitor, None);
-				log_trace!(logger, "Updating ChannelMonitor to id {}", update.update_id,);
-
-				// We hold a `pending_monitor_updates` lock through `update_monitor` to ensure we
-				// have well-ordered updates from the users' point of view. See the
-				// `pending_monitor_updates` docs for more.
-				let mut pending_monitor_updates =
-					monitor_state.pending_monitor_updates.lock().unwrap();
-				let update_res = monitor.update_monitor(
-					update,
-					&self.broadcaster,
-					&self.fee_estimator,
-					&self.logger,
-				);
-
-				let update_id = update.update_id;
-				let persist_res = if update_res.is_err() {
-					// Even if updating the monitor returns an error, the monitor's state will
-					// still be changed. Therefore, we should persist the updated monitor despite the error.
-					// We don't want to persist a `monitor_update` which results in a failure to apply later
-					// while reading `channel_monitor` with updates from storage. Instead, we should persist
-					// the entire `channel_monitor` here.
-					log_warn!(logger, "Failed to update ChannelMonitor. Going ahead and persisting the entire ChannelMonitor");
-					self.persister.update_persisted_channel(
-						monitor.persistence_key(),
-						None,
-						monitor,
-					)
-				} else {
-					self.persister.update_persisted_channel(
-						monitor.persistence_key(),
-						Some(update),
-						monitor,
-					)
-				};
-				match persist_res {
-					ChannelMonitorUpdateStatus::InProgress => {
-						pending_monitor_updates.push(update_id);
-						log_debug!(
-							logger,
-							"Persistence of ChannelMonitorUpdate id {:?} in progress",
-							update_id,
-						);
-					},
-					ChannelMonitorUpdateStatus::Completed => {
-						log_debug!(
-							logger,
-							"Persistence of ChannelMonitorUpdate id {:?} completed",
-							update_id,
-						);
-					},
-					ChannelMonitorUpdateStatus::UnrecoverableError => {
-						// Take the monitors lock for writing so that we poison it and any future
-						// operations going forward fail immediately.
-						core::mem::drop(pending_monitor_updates);
-						core::mem::drop(monitors);
-						let _poison = self.monitors.write().unwrap();
-						let err_str = "ChannelMonitor[Update] persistence failed unrecoverably. This indicates we cannot continue normal operation and must shut down.";
-						log_error!(logger, "{}", err_str);
-						panic!("{}", err_str);
-					},
-				}
-
-				// We may need to start monitoring for any alternative funding transactions.
-				if let Some(ref chain_source) = self.chain_source {
-					for (funding_outpoint, funding_script) in
-						update.internal_renegotiated_funding_data()
-					{
-						log_trace!(
-							logger,
-							"Registering renegotiated funding outpoint {} with the filter to monitor confirmations and spends",
-							funding_outpoint
-						);
-						chain_source.register_tx(&funding_outpoint.txid, &funding_script);
-						chain_source.register_output(WatchedOutput {
-							block_hash: None,
-							outpoint: funding_outpoint,
-							script_pubkey: funding_script,
-						});
-					}
-				}
-
-				if update_res.is_err() {
-					ChannelMonitorUpdateStatus::InProgress
-				} else {
-					persist_res
-				}
-			},
-		}
+		self.update_channel_internal(channel_id, update)
 	}
 
 	fn release_pending_monitor_events(