Make channel value optional for ChannelTransactionParameters::read

We'll need to support serializing `ChannelTransactionParameters` being
newly written, so there is no need for the required
`channel_value_satoshis` fallback.

Author: wpaulino

lightning/src/chain/onchaintx.rs

@@ -368,7 +368,7 @@ impl<'a, 'b, ES: EntropySource, SP: SignerProvider> ReadableArgs<(&'a ES, &'b SP
 		let prev_holder_commitment = Readable::read(reader)?;
 		let _prev_holder_htlc_sigs: Option<Vec<Option<(usize, Signature)>>> = Readable::read(reader)?;
 
-		let channel_parameters = ReadableArgs::<u64>::read(reader, channel_value_satoshis)?;
+		let channel_parameters = ReadableArgs::<Option<u64>>::read(reader, Some(channel_value_satoshis))?;
 
 		// Read the serialized signer bytes, but don't deserialize them, as we'll obtain our signer
 		// by re-deriving the private key material.

lightning/src/ln/chan_utils.rs

@@ -1034,8 +1034,8 @@ impl Writeable for ChannelTransactionParameters {
 	}
 }
 
-impl ReadableArgs<u64> for ChannelTransactionParameters {
-	fn read<R: io::Read>(reader: &mut R, read_args: u64) -> Result<Self, DecodeError> {
+impl ReadableArgs<Option<u64>> for ChannelTransactionParameters {
+	fn read<R: io::Read>(reader: &mut R, read_args: Option<u64>) -> Result<Self, DecodeError> {
 		let mut holder_pubkeys = RequiredWrapper(None);
 		let mut holder_selected_contest_delay = RequiredWrapper(None);
 		let mut is_outbound_from_holder = RequiredWrapper(None);
@@ -1058,10 +1058,17 @@ impl ReadableArgs<u64> for ChannelTransactionParameters {
 			(13, channel_value_satoshis, option),
 		});
 
-		let channel_value_satoshis = channel_value_satoshis.unwrap_or(read_args);
-		if channel_value_satoshis != read_args {
-			return Err(DecodeError::InvalidValue);
-		}
+		let channel_value_satoshis = match read_args {
+			None => channel_value_satoshis.ok_or(DecodeError::InvalidValue)?,
+			Some(expected_value) => {
+				let channel_value_satoshis = channel_value_satoshis.unwrap_or(expected_value);
+				if channel_value_satoshis == expected_value {
+					channel_value_satoshis
+				} else {
+					return Err(DecodeError::InvalidValue);
+				}
+			},
+		};
 
 		let mut additional_features = ChannelTypeFeatures::empty();
 		additional_features.set_anchors_nonzero_fee_htlc_tx_required();

lightning/src/ln/channel.rs

@@ -10862,7 +10862,7 @@ impl<'a, 'b, 'c, ES: Deref, SP: Deref> ReadableArgs<(&'a ES, &'b SP, &'c Channel
 			_ => return Err(DecodeError::InvalidValue),
 		};
 
-		let channel_parameters: ChannelTransactionParameters = ReadableArgs::<u64>::read(reader, channel_value_satoshis)?;
+		let channel_parameters: ChannelTransactionParameters = ReadableArgs::<Option<u64>>::read(reader, Some(channel_value_satoshis))?;
 		let funding_transaction: Option<Transaction> = Readable::read(reader)?;
 
 		let counterparty_cur_commitment_point = Readable::read(reader)?;

lightning/src/sign/mod.rs

@@ -124,7 +124,7 @@ impl_writeable_tlv_based!(DelayedPaymentOutputDescriptor, {
 	(8, revocation_pubkey, required),
 	(10, channel_keys_id, required),
 	(12, channel_value_satoshis, required),
-	(13, channel_transaction_parameters, (option: ReadableArgs, channel_value_satoshis.0.unwrap())),
+	(13, channel_transaction_parameters, (option: ReadableArgs, Some(channel_value_satoshis.0.unwrap()))),
 });
 
 pub(crate) const P2WPKH_WITNESS_WEIGHT: u64 = 1 /* num stack items */ +
@@ -199,7 +199,7 @@ impl_writeable_tlv_based!(StaticPaymentOutputDescriptor, {
 	(2, output, required),
 	(4, channel_keys_id, required),
 	(6, channel_value_satoshis, required),
-	(7, channel_transaction_parameters, (option: ReadableArgs, channel_value_satoshis.0.unwrap())),
+	(7, channel_transaction_parameters, (option: ReadableArgs, Some(channel_value_satoshis.0.unwrap()))),
 });
 
 /// Describes the necessary information to spend a spendable output.
@@ -559,7 +559,7 @@ pub struct ChannelDerivationParameters {
 impl_writeable_tlv_based!(ChannelDerivationParameters, {
 	(0, value_satoshis, required),
 	(2, keys_id, required),
-	(4, transaction_parameters, (required: ReadableArgs, value_satoshis.0.unwrap())),
+	(4, transaction_parameters, (required: ReadableArgs, Some(value_satoshis.0.unwrap()))),
 });
 
 /// A descriptor used to sign for a commitment transaction's HTLC output.