lnwallet: eliminate usage of LightningChannel.theirPrevPkScript

This commit removes the theirPrevPkScript field from the
LightningChannel struct all together. It’s no longer needed as the more
fundamental mutation bug has been fixed within the channel state
machine.

lnwallet/channel.go

@@ -276,7 +276,7 @@ func (c *commitment) toChannelDelta(ourCommit bool) (*channeldb.ChannelDelta, er
 			found bool
 		)
 
-		pkScript := p.theirPrevPkScript
+		pkScript := p.theirPkScript
 		if ourCommit {
 			pkScript = p.ourPkScript
 		}
@@ -294,8 +294,8 @@ func (c *commitment) toChannelDelta(ourCommit bool) (*channeldb.ChannelDelta, er
 			}
 		}
 		if !found {
-			return 0, fmt.Errorf("could not find a matching " +
-				"output for the HTLC in the commitment transaction")
+			return 0, fmt.Errorf("unable to find htlc: script=%x, value=%v",
+				pkScript, p.Amount)
 		}
 
 		return idx, nil
@@ -309,8 +309,8 @@ func (c *commitment) toChannelDelta(ourCommit bool) (*channeldb.ChannelDelta, er
 		if (ourCommit && htlc.isDustLocal) ||
 			(!ourCommit && htlc.isDustRemote) {
 			index = maxUint16
-		} else if index, err = locateOutputIndex(htlc); err != nil {
-			return nil, err
+		} else if index, err = locateOutputIndex(&htlc); err != nil {
+			return nil, fmt.Errorf("unable to find outgoing htlc: %v", err)
 		}
 
 		h := &channeldb.HTLC{
@@ -328,8 +328,8 @@ func (c *commitment) toChannelDelta(ourCommit bool) (*channeldb.ChannelDelta, er
 		if (ourCommit && htlc.isDustLocal) ||
 			(!ourCommit && htlc.isDustRemote) {
 			index = maxUint16
-		} else if index, err = locateOutputIndex(htlc); err != nil {
-			return nil, err
+		} else if index, err = locateOutputIndex(&htlc); err != nil {
+			return nil, fmt.Errorf("unable to find incoming htlc: %v", err)
 		}
 
 		h := &channeldb.HTLC{
@@ -2075,12 +2075,6 @@ func (lc *LightningChannel) SettleHTLC(preimage [32]byte) (uint64, error) {
 
 	lc.localUpdateLog.appendUpdate(pd)
 
-	// Since we will not be adding this HTLC to any commitment transaction
-	// anymore, we should properly set theirPrevPkScript so we can generate
-	// a valid ChannelDelta for a revoked remote commitment.
-	addEntry := lc.remoteUpdateLog.lookup(targetHTLC.Index)
-	addEntry.theirPrevPkScript = addEntry.theirPkScript
-
 	lc.rHashMap[paymentHash][0] = nil
 	lc.rHashMap[paymentHash] = lc.rHashMap[paymentHash][1:]
 	if len(lc.rHashMap[paymentHash]) == 0 {
@@ -2117,12 +2111,6 @@ func (lc *LightningChannel) ReceiveHTLCSettle(preimage [32]byte, logIndex uint64
 	}
 
 	lc.remoteUpdateLog.appendUpdate(pd)
-
-	// Since we will not be adding this HTLC to any commitment transaction
-	// anymore, we should properly set theirPrevPkScript so we can generate
-	// a valid ChannelDelta for a revoked remote commitment.
-	htlc.theirPrevPkScript = htlc.theirPkScript
-
 	return nil
 }
 
@@ -2150,11 +2138,6 @@ func (lc *LightningChannel) FailHTLC(rHash [32]byte) (uint64, error) {
 
 	lc.localUpdateLog.appendUpdate(pd)
 
-	// Since we will not be adding this HTLC to any commitment transaction
-	// anymore, we should properly set theirPrevPkScript so we can generate
-	// a valid ChannelDelta for a revoked remote commitment.
-	addEntry.theirPrevPkScript = addEntry.theirPkScript
-
 	lc.rHashMap[rHash][0] = nil
 	lc.rHashMap[rHash] = lc.rHashMap[rHash][1:]
 	if len(lc.rHashMap[rHash]) == 0 {
@@ -2187,11 +2170,6 @@ func (lc *LightningChannel) ReceiveFailHTLC(logIndex uint64) error {
 
 	lc.remoteUpdateLog.appendUpdate(pd)
 
-	// Since we will not be adding this HTLC to any commitment transaction
-	// anymore, we should properly set theirPrevPkScript so we can generate
-	// a valid ChannelDelta for a revoked remote commitment.
-	htlc.theirPrevPkScript = htlc.theirPkScript
-
 	return nil
 }
 
@@ -2282,7 +2260,6 @@ func (lc *LightningChannel) addHTLC(commitTx *wire.MsgTx, ourCommit bool,
 	if ourCommit {
 		paymentDesc.ourPkScript = htlcP2WSH
 	} else {
-		paymentDesc.theirPrevPkScript = paymentDesc.theirPkScript
 		paymentDesc.theirPkScript = htlcP2WSH
 	}