lnwallet: extract initMusigNonce from initRevocationWindows

This'll be useful later to make some enhancements to the existing unit
tests.

lnwallet/test_utils.go

@@ -419,6 +419,28 @@ func CreateTestChannels(t *testing.T, chanType channeldb.ChannelType,
 	return channelAlice, channelBob, nil
 }
 
+// initMusigNonce is used to manually setup musig2 nonces for a new channel,
+// outside the normal chan-reest flow.
+func initMusigNonce(chanA, chanB *LightningChannel) error {
+	chanANonces, err := chanA.GenMusigNonces()
+	if err != nil {
+		return err
+	}
+	chanBNonces, err := chanB.GenMusigNonces()
+	if err != nil {
+		return err
+	}
+
+	if err := chanA.InitRemoteMusigNonces(chanBNonces); err != nil {
+		return err
+	}
+	if err := chanB.InitRemoteMusigNonces(chanANonces); err != nil {
+		return err
+	}
+
+	return nil
+}
+
 // initRevocationWindows simulates a new channel being opened within the p2p
 // network by populating the initial revocation windows of the passed
 // commitment state machines.
@@ -427,19 +449,7 @@ func initRevocationWindows(chanA, chanB *LightningChannel) error {
 	// either FundingLocked or ChannelReestablish by calling
 	// InitRemoteMusigNonces for both sides.
 	if chanA.channelState.ChanType.IsTaproot() {
-		chanANonces, err := chanA.GenMusigNonces()
+		if err := initMusigNonce(chanA, chanB); err != nil {
-		if err != nil {
-			return err
-		}
-		chanBNonces, err := chanB.GenMusigNonces()
-		if err != nil {
-			return err
-		}
-
-		if err := chanA.InitRemoteMusigNonces(chanBNonces); err != nil {
-			return err
-		}
-		if err := chanB.InitRemoteMusigNonces(chanANonces); err != nil {
 			return err
 		}
 	}