fix Define serialization on Option<TransactionU16LenLimited>

Author: optout21

lightning/src/ln/msgs.rs

@@ -2667,11 +2667,11 @@ impl_writeable_msg!(SpliceLocked, {
 impl_writeable_msg!(TxAddInput, {
 	channel_id,
 	serial_id,
+	prevtx,
 	prevtx_out,
 	sequence,
 }, {
-	(0, prevtx, option),
-	(1, shared_input_txid, option), // `funding_txid`
+	(0, shared_input_txid, option), // `funding_txid`
 });
 
 impl_writeable_msg!(TxAddOutput, {
@@ -5230,10 +5230,28 @@ mod tests {
 			}).unwrap()),
 			prevtx_out: 305419896,
 			sequence: 305419896,
-			shared_input_txid: Some(Txid::from_str("c2d4449afa8d26140898dd54d3390b057ba2a5afcf03ba29d7dc0d8b9ffe966e").unwrap()),
+			shared_input_txid: None,
 		};
 		let encoded_value = tx_add_input.encode();
-		let target_value = "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";
+		let target_value = "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";
+		assert_eq!(encoded_value.as_hex().to_string(), target_value);
+	}
+
+	#[test]
+	fn encoding_tx_add_input_shared() {
+		let tx_add_input = msgs::TxAddInput {
+			channel_id: ChannelId::from_bytes([2; 32]),
+			serial_id: 4886718345,
+			prevtx: None,
+			prevtx_out: 305419896,
+			sequence: 305419896,
+			shared_input_txid: Some(
+				Txid::from_str("c2d4449afa8d26140898dd54d3390b057ba2a5afcf03ba29d7dc0d8b9ffe966e")
+					.unwrap(),
+			),
+		};
+		let encoded_value = tx_add_input.encode();
+		let target_value = "020202020202020202020202020202020202020202020202020202020202020200000001234567890000123456781234567800206e96fe9f8b0ddcd729ba03cfafa5a27b050b39d354dd980814268dfa9a44d4c2";
 		assert_eq!(encoded_value.as_hex().to_string(), target_value);
 	}
 

lightning/src/util/ser.rs

@@ -1691,22 +1691,30 @@ impl TransactionU16LenLimited {
 	}
 }
 
-impl Writeable for TransactionU16LenLimited {
+impl Writeable for Option<TransactionU16LenLimited> {
 	fn write<W: Writer>(&self, w: &mut W) -> Result<(), io::Error> {
-		(self.0.serialized_length() as u16).write(w)?;
-		self.0.write(w)
+		match self {
+			Some(tx) => {
+				(tx.0.serialized_length() as u16).write(w)?;
+				tx.0.write(w)
+			},
+			None => 0u16.write(w),
+		}
 	}
 }
 
-impl Readable for TransactionU16LenLimited {
+impl Readable for Option<TransactionU16LenLimited> {
 	fn read<R: Read>(r: &mut R) -> Result<Self, DecodeError> {
 		let len = <u16 as Readable>::read(r)?;
+		if len == 0 {
+			return Ok(None);
+		}
 		let mut tx_reader = FixedLengthReader::new(r, len as u64);
 		let tx: Transaction = Readable::read(&mut tx_reader)?;
 		if tx_reader.bytes_remain() {
 			Err(DecodeError::BadLengthDescriptor)
 		} else {
-			Ok(Self(tx))
+			Ok(Some(TransactionU16LenLimited(tx)))
 		}
 	}
 }