Test register_output is called on dependent txn

chain::Filter::register_output may return an in-block dependent
transaction that spends the output. Test the scenario where the txdata
given to ChainMonitor::block_connected includes a commitment transaction
whose HTLC output is spent in the same block but not included in txdata.
Instead, it is returned by chain::Filter::register_output when given the
commitment transaction's HTLC output. This is a common scenario for
Electrum clients, which provided filtered txdata.

Author: jkczyz

lightning/src/chain/chainmonitor.rs

@@ -267,3 +267,57 @@ impl<ChannelSigner: Sign, C: Deref, T: Deref, F: Deref, L: Deref, P: Deref> even
 		pending_events
 	}
 }
+
+#[cfg(test)]
+mod tests {
+	use ::{check_added_monitors, get_local_commitment_txn};
+	use ln::features::InitFeatures;
+	use ln::functional_test_utils::*;
+	use util::events::EventsProvider;
+	use util::events::MessageSendEventsProvider;
+	use util::test_utils::{OnRegisterOutput, TxOutReference};
+
+	use bitcoin::blockdata::block::{Block, BlockHeader};
+
+	/// Tests that in-block dependent transactions are processed by `block_connected` when not
+	/// included in `txdata` but returned by [`chain::Filter::register_output`]. For instance,
+	/// a commitment transaction's HTLC output may be spent in the same block as the commitment
+	/// transaction itself. An Electrum client may filter the commitment transaction but needs to
+	/// return the HTLC transaction so it can be processed.
+	#[test]
+	fn connect_block_checks_dependent_transactions() {
+		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);
+		let channel = create_announced_chan_between_nodes(&nodes, 0, 1, InitFeatures::known(), InitFeatures::known());
+
+		// Send a payment, saving nodes[0]'s revoked commitment and HTLC-Timeout transactions.
+		let (commitment_tx, htlc_tx) = {
+			let payment_preimage = route_payment(&nodes[0], &vec!(&nodes[1])[..], 5_000_000).0;
+			let mut txn = get_local_commitment_txn!(nodes[0], channel.2);
+			claim_payment(&nodes[0], &vec!(&nodes[1])[..], payment_preimage, 5_000_000);
+
+			assert_eq!(txn.len(), 2);
+			(txn.remove(0), txn.remove(0))
+		};
+
+		// Set expectations on nodes[1]'s chain source to return dependent transactions.
+		let htlc_output = TxOutReference(commitment_tx.clone(), 0);
+		let to_local_output = TxOutReference(commitment_tx.clone(), 1);
+		let htlc_timeout_output = TxOutReference(htlc_tx.clone(), 0);
+		nodes[1].chain_source
+			.expect(OnRegisterOutput { with: htlc_output, returns: Some((1, htlc_tx)) })
+			.expect(OnRegisterOutput { with: to_local_output, returns: None })
+			.expect(OnRegisterOutput { with: htlc_timeout_output, returns: None });
+
+		// Notify nodes[1] that nodes[0]'s revoked commitment transaction was mined. The chain
+		// source should return the dependent HTLC transaction when the HTLC output is registered.
+		mine_transaction(&nodes[1], &commitment_tx);
+
+		// Clean up so uninteresting assertions don't fail.
+		check_added_monitors!(nodes[1], 1);
+		nodes[1].node.get_and_clear_pending_msg_events();
+		nodes[1].node.get_and_clear_pending_events();
+	}
+}

lightning/src/ln/functional_test_utils.rs

@@ -341,7 +341,8 @@ macro_rules! get_feerate {
 	}
 }
 
-#[cfg(test)]
+/// Returns any local commitment transactions for the channel.
+#[macro_export]
 macro_rules! get_local_commitment_txn {
 	($node: expr, $channel_id: expr) => {
 		{