Return an Option from ChannelContext::get_initial_commitment_signed

When ChannelContext::get_initial_commitment_signed is called for V2
channel establishment, any errors should result in closing the channel.
However, in the future, when this is used for splicing it should abort
instead of closing the channel. Move the error construction to the call
sites in anticipation of this.

Author: jkczyz

lightning/src/ln/channel.rs

@@ -2965,10 +2965,15 @@ where
 		self.context.assert_no_commitment_advancement(transaction_number, "initial commitment_signed");
 		let commitment_signed = self.context.get_initial_commitment_signed(&self.funding, logger);
 		let commitment_signed = match commitment_signed {
-			Ok(commitment_signed) => commitment_signed,
-			Err(err) => {
+			Some(commitment_signed) => commitment_signed,
+			None => {
 				self.funding.channel_transaction_parameters.funding_outpoint = None;
-				return Err(ChannelError::Close((err.to_string(), ClosureReason::HolderForceClosed { broadcasted_latest_txn: Some(false) })));
+				return Err(ChannelError::Close(
+						(
+							"Failed to get signatures for new commitment_signed".to_owned(),
+							ClosureReason::HolderForceClosed { broadcasted_latest_txn: Some(false) },
+						)
+				));
 			},
 		};
 
@@ -5494,7 +5499,7 @@ where
 	#[rustfmt::skip]
 	fn get_initial_counterparty_commitment_signature<L: Deref>(
 		&self, funding: &FundingScope, logger: &L
-	) -> Result<Signature, ChannelError>
+	) -> Option<Signature>
 	where
 		SP::Target: SignerProvider,
 		L::Target: Logger
@@ -5509,11 +5514,7 @@ where
 				let channel_parameters = &funding.channel_transaction_parameters;
 				ecdsa.sign_counterparty_commitment(channel_parameters, &counterparty_initial_commitment_tx, Vec::new(), Vec::new(), &self.secp_ctx)
 					.map(|(signature, _)| signature)
-					.map_err(|_| ChannelError::Close(
-						(
-							"Failed to get signatures for new commitment_signed".to_owned(),
-							ClosureReason::HolderForceClosed { broadcasted_latest_txn: Some(false) },
-						)))
+					.ok()
 			},
 			// TODO (taproot|arik)
 			#[cfg(taproot)]
@@ -5524,38 +5525,35 @@ where
 	#[rustfmt::skip]
 	fn get_initial_commitment_signed<L: Deref>(
 		&mut self, funding: &FundingScope, logger: &L
-	) -> Result<msgs::CommitmentSigned, ChannelError>
+	) -> Option<msgs::CommitmentSigned>
 	where
 		SP::Target: SignerProvider,
 		L::Target: Logger
 	{
 		assert!(matches!(self.channel_state, ChannelState::FundingNegotiated(_)));
 
-		let signature = match self.get_initial_counterparty_commitment_signature(funding, logger) {
-			Ok(res) => res,
-			Err(e) => {
-				log_error!(logger, "Got bad signatures: {:?}!", e);
-				return Err(e);
-			}
-		};
-
-		log_info!(logger, "Generated commitment_signed for peer for channel {}", &self.channel_id());
-
-		Ok(msgs::CommitmentSigned {
-			channel_id: self.channel_id,
-			htlc_signatures: vec![],
-			signature,
-			funding_txid: funding.get_funding_txo().map(|funding_txo| funding_txo.txid),
-			#[cfg(taproot)]
-			partial_signature_with_nonce: None,
-		})
+		let signature = self.get_initial_counterparty_commitment_signature(funding, logger);
+		if let Some(signature) = signature {
+			log_info!(logger, "Generated commitment_signed for peer for channel {}", &self.channel_id());
+			Some(msgs::CommitmentSigned {
+				channel_id: self.channel_id,
+				htlc_signatures: vec![],
+				signature,
+				funding_txid: funding.get_funding_txo().map(|funding_txo| funding_txo.txid),
+				#[cfg(taproot)]
+				partial_signature_with_nonce: None,
+			})
+		} else {
+			// TODO: Support async signing
+			None
+		}
 	}
 
 	#[cfg(all(test))]
 	pub fn get_initial_counterparty_commitment_signature_for_test<L: Deref>(
 		&mut self, funding: &mut FundingScope, logger: &L,
 		counterparty_cur_commitment_point_override: PublicKey,
-	) -> Result<Signature, ChannelError>
+	) -> Option<Signature>
 	where
 		SP::Target: SignerProvider,
 		L::Target: Logger,
@@ -8426,7 +8424,14 @@ where
 							// if it has not received tx_signatures for that funding transaction AND
 							// if next_commitment_number is zero:
 							//   MUST retransmit its commitment_signed for that funding transaction.
-							let commitment_signed = self.context.get_initial_commitment_signed(&self.funding, logger)?;
+							let commitment_signed = self.context.get_initial_commitment_signed(&self.funding, logger)
+								// TODO Support async signing
+								.ok_or_else(|| ChannelError::Close(
+										(
+											"Failed to get signatures for new commitment_signed".to_owned(),
+											ClosureReason::HolderForceClosed { broadcasted_latest_txn: Some(false) },
+										)
+								))?;
 							Some(msgs::CommitmentUpdate {
 								commitment_signed: vec![commitment_signed],
 								update_add_htlcs: vec![],