🐛 [backend/eth] conclude after progression into final

Signed-off-by: Matthias Geihs <matthias@perun.network>

Author: matthiasgeihs

backend/ethereum/channel/conclude.go

@@ -54,8 +54,8 @@ func (a *Adjudicator) ensureConcluded(ctx context.Context, req channel.Adjudicat
 	subErr := make(chan error, 1)
 	waitCtx, cancel := context.WithCancel(ctx)
 	go func() {
+		defer cancel()
 		subErr <- sub.Read(ctx, events)
-		cancel()
 	}()
 
 	// In final Register calls, as the non-initiator, we optimistically wait for
@@ -71,17 +71,12 @@ func (a *Adjudicator) ensureConcluded(ctx context.Context, req channel.Adjudicat
 	}
 
 	// No conclude event found in the past, send transaction.
-	if req.Tx.IsFinal {
-		err = errors.WithMessage(a.callConcludeFinal(ctx, req), "calling concludeFinal")
-	} else {
-		err = errors.WithMessage(a.callConclude(ctx, req, subStates), "calling conclude")
-	}
-	if IsErrTxFailed(err) {
-		a.log.Warn("Calling conclude(Final) failed, waiting for event anyways...")
-	} else if err != nil {
-		return err
+	err = a.conclude(ctx, req, subStates)
+	if err != nil {
+		return errors.WithMessage(err, "concluding")
 	}
 
+	// Wait for concluded event.
 	for {
 		select {
 		case _e := <-events:
@@ -100,6 +95,25 @@ func (a *Adjudicator) ensureConcluded(ctx context.Context, req channel.Adjudicat
 	}
 }
 
+func (a *Adjudicator) conclude(ctx context.Context, req channel.AdjudicatorReq, subStates channel.StateMap) error {
+	// If the on-chain state resulted from forced execution, we do not have a fully-signed state and cannot call concludeFinal.
+	forceExecuted, err := a.isForceExecuted(ctx, req.Params.ID())
+	if err != nil {
+		return errors.WithMessage(err, "checking force execution")
+	}
+	if req.Tx.IsFinal && !forceExecuted {
+		err = errors.WithMessage(a.callConcludeFinal(ctx, req), "calling concludeFinal")
+	} else {
+		err = errors.WithMessage(a.callConclude(ctx, req, subStates), "calling conclude")
+	}
+	if IsErrTxFailed(err) {
+		a.log.WithError(err).Warn("Calling conclude(Final) failed, waiting for event anyways...")
+	} else if err != nil {
+		return err
+	}
+	return nil
+}
+
 // isConcluded returns whether a channel is already concluded.
 func (a *Adjudicator) isConcluded(ctx context.Context, sub *subscription.EventSub) (bool, error) {
 	events := make(chan *subscription.Event, 10)
@@ -119,6 +133,36 @@ func (a *Adjudicator) isConcluded(ctx context.Context, sub *subscription.EventSu
 	return false, errors.WithMessage(<-subErr, "reading past events")
 }
 
+// isForceExecuted returns whether a channel is in the forced execution phase.
+func (a *Adjudicator) isForceExecuted(_ctx context.Context, c channel.ID) (bool, error) {
+	ctx, cancel := context.WithCancel(_ctx)
+	defer cancel()
+	sub, err := subscription.NewEventSub(ctx, a.ContractBackend, a.bound, updateEventType(c), startBlockOffset)
+	if err != nil {
+		return false, errors.WithMessage(err, "subscribing")
+	}
+	defer sub.Close()
+	events := make(chan *subscription.Event, 10)
+	subErr := make(chan error, 1)
+	// Write the events into events.
+	go func() {
+		defer close(events)
+		subErr <- sub.ReadPast(ctx, events)
+	}()
+	// Read all events and check for force execution.
+	var lastEvent *subscription.Event
+	for _e := range events {
+		lastEvent = _e
+	}
+	if lastEvent != nil {
+		e := lastEvent.Data.(*adjudicator.AdjudicatorChannelUpdate)
+		if e.Phase == phaseForceExec {
+			return true, nil
+		}
+	}
+	return false, errors.WithMessage(<-subErr, "reading past events")
+}
+
 func updateEventType(channelID [32]byte) subscription.EventFactory {
 	return func() *subscription.Event {
 		return &subscription.Event{