routing: convert to nillable failure reason

This commit converts several functions from returning a bool and a
failure reason to a nillable failure reason as return parameter. This
will take away confusion about the interpretation of the two separate
values.

routing/missioncontrol.go

@@ -420,12 +420,11 @@ func (m *MissionControl) GetHistorySnapshot() *MissionControlSnapshot {
 // ReportPaymentFail reports a failed payment to mission control as input for
 // future probability estimates. The failureSourceIdx argument indicates the
 // failure source. If it is nil, the failure source is unknown. This function
-// returns a bool indicating whether this error is a final error. If it is
-// final, a failure reason is returned and no further payment attempts need to
-// be made.
+// returns a reason if this failure is a final failure. In that case no further
+// payment attempts need to be made.
 func (m *MissionControl) ReportPaymentFail(paymentID uint64, rt *route.Route,
-	failureSourceIdx *int, failure lnwire.FailureMessage) (bool,
-	channeldb.FailureReason, error) {
+	failureSourceIdx *int, failure lnwire.FailureMessage) (
+	*channeldb.FailureReason, error) {
 
 	timestamp := m.now()
 
@@ -442,13 +441,18 @@ func (m *MissionControl) ReportPaymentFail(paymentID uint64, rt *route.Route,
 
 	// Store complete result in database.
 	if err := m.store.AddResult(result); err != nil {
-		return false, 0, err
+		return nil, err
 	}
 
 	// Apply result to update mission control state.
 	final, reason := m.applyPaymentResult(result)
 
-	return final, reason, nil
+	// Convert final bool and reason to nillable reason.
+	if final {
+		return &reason, nil
+	}
+
+	return nil, nil
 }
 
 // applyPaymentResult applies a payment result as input for future probability

routing/mock_test.go

@@ -98,11 +98,11 @@ type mockMissionControl struct {
 
 var _ MissionController = (*mockMissionControl)(nil)
 
-func (m *mockMissionControl) ReportPaymentFail(paymentID uint64,
-	rt *route.Route, failureSourceIdx *int, failure lnwire.FailureMessage) (
-	bool, channeldb.FailureReason, error) {
+func (m *mockMissionControl) ReportPaymentFail(paymentID uint64, rt *route.Route,
+	failureSourceIdx *int, failure lnwire.FailureMessage) (
+	*channeldb.FailureReason, error) {
 
-	return false, 0, nil
+	return nil, nil
 }
 
 func (m *mockMissionControl) GetProbability(fromNode, toNode route.Vertex,

routing/payment_lifecycle.go

@@ -342,10 +342,10 @@ func (p *paymentLifecycle) sendPaymentAttempt(firstHop lnwire.ShortChannelID,
 // whether we should make another payment attempt.
 func (p *paymentLifecycle) handleSendError(sendErr error) error {
 
-	final, reason := p.router.processSendError(
+	reason := p.router.processSendError(
 		p.attempt.PaymentID, &p.attempt.Route, sendErr,
 	)
-	if !final {
+	if reason == nil {
 		// Save the forwarding error so it can be returned if
 		// this turns out to be the last attempt.
 		p.lastError = sendErr
@@ -354,14 +354,14 @@ func (p *paymentLifecycle) handleSendError(sendErr error) error {
 	}
 
 	log.Debugf("Payment %x failed: final_outcome=%v, raw_err=%v",
-		p.payment.PaymentHash, reason, sendErr)
+		p.payment.PaymentHash, *reason, sendErr)
 
 	// Mark the payment failed with no route.
 	//
 	// TODO(halseth): make payment codes for the actual reason we don't
 	// continue path finding.
 	err := p.router.cfg.Control.Fail(
-		p.payment.PaymentHash, reason,
+		p.payment.PaymentHash, *reason,
 	)
 	if err != nil {
 		return err

routing/router.go

@@ -179,8 +179,8 @@ type MissionController interface {
 	// whether this error is a final error and no further payment attempts
 	// need to be made.
 	ReportPaymentFail(paymentID uint64, rt *route.Route,
-		failureSourceIdx *int, failure lnwire.FailureMessage) (bool,
-		channeldb.FailureReason, error)
+		failureSourceIdx *int, failure lnwire.FailureMessage) (
+		*channeldb.FailureReason, error)
 
 	// GetProbability is expected to return the success probability of a
 	// payment from fromNode along edge.
@@ -1887,23 +1887,25 @@ func (r *ChannelRouter) tryApplyChannelUpdate(rt *route.Route,
 // to continue with an alternative route. This is indicated by the boolean
 // return value.
 func (r *ChannelRouter) processSendError(paymentID uint64, rt *route.Route,
-	sendErr error) (bool, channeldb.FailureReason) {
+	sendErr error) *channeldb.FailureReason {
 
-	reportFail := func(srcIdx *int, msg lnwire.FailureMessage) (bool,
-		channeldb.FailureReason) {
+	internalErrorReason := channeldb.FailureReasonError
+
+	reportFail := func(srcIdx *int,
+		msg lnwire.FailureMessage) *channeldb.FailureReason {
 
 		// Report outcome to mission control.
-		final, reason, err := r.cfg.MissionControl.ReportPaymentFail(
+		reason, err := r.cfg.MissionControl.ReportPaymentFail(
 			paymentID, rt, srcIdx, msg,
 		)
 		if err != nil {
 			log.Errorf("Error reporting payment result to mc: %v",
 				err)
 
-			return true, channeldb.FailureReasonError
+			return &internalErrorReason
 		}
 
-		return final, reason
+		return reason
 	}
 
 	if sendErr == htlcswitch.ErrUnreadableFailureMessage {
@@ -1915,7 +1917,7 @@ func (r *ChannelRouter) processSendError(paymentID uint64, rt *route.Route,
 	// trying.
 	fErr, ok := sendErr.(*htlcswitch.ForwardingError)
 	if !ok {
-		return true, channeldb.FailureReasonError
+		return &internalErrorReason
 	}
 
 	failureMessage := fErr.FailureMessage
@@ -1928,7 +1930,7 @@ func (r *ChannelRouter) processSendError(paymentID uint64, rt *route.Route,
 			rt, failureSourceIdx, failureMessage,
 		)
 		if err != nil {
-			return true, channeldb.FailureReasonError
+			return &internalErrorReason
 		}
 	}