Errors are no longer a special case in the EDS.

And changing event queue so that Pullers don't have to process an error.

event/event.go

@@ -73,21 +73,8 @@ func newSubscriber(filter []terminalapi.Event, cb Callback) *subscriber {
 // Terminates when the context expires.
 func (s *subscriber) run(ctx context.Context) {
 	for {
-		e, err := s.queue.Pull(ctx)
-		if err != nil {
-			e = terminalapi.NewErrorf("failed to pull event off the queue: %v", err)
-		}
-
-		switch ev := e.(type) {
-		case *terminalapi.Error:
-			// Don't forward the error if the context is closed.
-			select {
-			case <-ctx.Done():
-			default:
-				s.cb(ev)
-			}
-
-		default:
+		ev := s.queue.Pull(ctx)
+		if ev != nil {
 			s.cb(ev)
 		}
 
@@ -105,9 +92,8 @@ func (s *subscriber) event(ev terminalapi.Event) {
 		s.queue.Push(ev)
 	}
 
-	var errT *terminalapi.Error
 	t := reflect.TypeOf(ev)
-	if t == reflect.TypeOf(errT) || s.filter[t] {
+	if s.filter[t] {
 		s.queue.Push(ev)
 	}
 }
@@ -167,9 +153,6 @@ type StopFunc func()
 // all kinds. If the filter is non-empty, only events of the provided type will
 // be sent to the subscriber.
 // Returns a function that allows the subscriber to unsubscribe.
-//
-// Subscribers cannot filter out event type terminalapi.Error which is used to
-// forward errors to the Callback.
 func (eds *DistributionSystem) Subscribe(filter []terminalapi.Event, cb Callback) StopFunc {
 	eds.mu.Lock()
 	defer eds.mu.Unlock()

event/event_test.go

@@ -187,7 +187,7 @@ func TestDistributionSystem(t *testing.T) {
 			},
 		},
 		{
-			desc: "single subscriber, errors are always received",
+			desc: "single subscriber, wants errors only",
 			events: []terminalapi.Event{
 				&terminalapi.Keyboard{Key: keyboard.KeyEnter},
 				&terminalapi.Mouse{Position: image.Point{1, 1}},
@@ -197,14 +197,11 @@ func TestDistributionSystem(t *testing.T) {
 			subCase: []*subscriberCase{
 				{
 					filter: []terminalapi.Event{
-						&terminalapi.Keyboard{},
-						&terminalapi.Mouse{},
+						terminalapi.NewError(""),
 					},
 					rec: newReceiver(receiverModeReceive),
 					want: map[terminalapi.Event]bool{
-						&terminalapi.Keyboard{Key: keyboard.KeyEnter}:   true,
-						&terminalapi.Mouse{Position: image.Point{1, 1}}: true,
-						terminalapi.NewError("error"):                   true,
+						terminalapi.NewError("error"): true,
 					},
 				},
 			},
@@ -230,8 +227,6 @@ func TestDistributionSystem(t *testing.T) {
 					want: map[terminalapi.Event]bool{
 						&terminalapi.Keyboard{Key: keyboard.KeyEnter}: true,
 						&terminalapi.Keyboard{Key: keyboard.KeyEsc}:   true,
-						terminalapi.NewError("error1"):                true,
-						terminalapi.NewError("error2"):                true,
 					},
 				},
 				{
@@ -245,8 +240,6 @@ func TestDistributionSystem(t *testing.T) {
 						&terminalapi.Mouse{Position: image.Point{1, 1}}: true,
 						&terminalapi.Resize{Size: image.Point{1, 1}}:    true,
 						&terminalapi.Resize{Size: image.Point{2, 2}}:    true,
-						terminalapi.NewError("error1"):                  true,
-						terminalapi.NewError("error2"):                  true,
 					},
 				},
 			},
@@ -268,8 +261,6 @@ func TestDistributionSystem(t *testing.T) {
 					want: map[terminalapi.Event]bool{
 						&terminalapi.Keyboard{Key: keyboard.KeyEnter}: true,
 						&terminalapi.Keyboard{Key: keyboard.KeyEsc}:   true,
-						terminalapi.NewError("error1"):                true,
-						terminalapi.NewError("error2"):                true,
 					},
 				},
 				{
@@ -280,8 +271,6 @@ func TestDistributionSystem(t *testing.T) {
 					want: map[terminalapi.Event]bool{
 						&terminalapi.Keyboard{Key: keyboard.KeyEnter}: true,
 						&terminalapi.Keyboard{Key: keyboard.KeyEsc}:   true,
-						terminalapi.NewError("error1"):                true,
-						terminalapi.NewError("error2"):                true,
 					},
 					wantErr: true,
 				},

event/eventqueue/eventqueue.go

@@ -124,10 +124,10 @@ func (u *Unbound) Pop() terminalapi.Event {
 }
 
 // Pull is like Pop(), but blocks until an item is available or the context
-// expires.
-func (u *Unbound) Pull(ctx context.Context) (terminalapi.Event, error) {
+// expires. Returns a nil event if the context expired.
+func (u *Unbound) Pull(ctx context.Context) terminalapi.Event {
 	if e := u.Pop(); e != nil {
-		return e, nil
+		return e
 	}
 
 	u.cond.L.Lock()
@@ -135,12 +135,12 @@ func (u *Unbound) Pull(ctx context.Context) (terminalapi.Event, error) {
 	for {
 		select {
 		case <-ctx.Done():
-			return nil, ctx.Err()
+			return nil
 		default:
 		}
 
 		if e := u.Pop(); e != nil {
-			return e, nil
+			return e
 		}
 		u.cond.Wait()
 	}

event/eventqueue/eventqueue_test.go

@@ -84,10 +84,7 @@ func TestPullEventAvailable(t *testing.T) {
 	q.Push(want)
 
 	ctx := context.Background()
-	got, err := q.Pull(ctx)
-	if err != nil {
-		t.Fatalf("Pull => unexpected error: %v", err)
-	}
+	got := q.Pull(ctx)
 	if diff := pretty.Compare(want, got); diff != "" {
 		t.Errorf("Pull => unexpected diff (-want, +got):\n%s", diff)
 	}
@@ -107,16 +104,12 @@ func TestPullBlocksUntilAvailable(t *testing.T) {
 	ctx, cancel := context.WithTimeout(context.Background(), 1*time.Millisecond)
 	defer cancel()
 
-	if _, err := q.Pull(ctx); err == nil {
-		t.Fatal("Pull => expected timeout error, got nil")
+	if got := q.Pull(ctx); got != nil {
+		t.Fatalf("Pull => %v, want <nil>", got)
 	}
 
 	close(ch)
-	got, err := q.Pull(context.Background())
-	if err != nil {
-		t.Fatalf("Pull => unexpected error: %v", err)
-	}
-
+	got := q.Pull(context.Background())
 	if diff := pretty.Compare(want, got); diff != "" {
 		t.Errorf("Pull => unexpected diff (-want, +got):\n%s", diff)
 	}

terminal/faketerm/faketerm.go

@@ -195,9 +195,9 @@ func (t *Terminal) Event(ctx context.Context) terminalapi.Event {
 		return terminalapi.NewErrorf("no event queue provided, use the WithEventQueue option when creating the fake terminal")
 	}
 
-	ev, err := t.events.Pull(ctx)
-	if err != nil {
-		return terminalapi.NewErrorf("unable to pull the next event: %v", err)
+	ev := t.events.Pull(ctx)
+	if ev == nil {
+		return terminalapi.NewError("unable to pull the next event")
 	}
 
 	if res, ok := ev.(*terminalapi.Resize); ok {

terminal/termbox/termbox.go

@@ -148,9 +148,9 @@ func (t *Terminal) pollEvents() {
 
 // Event implements terminalapi.Terminal.Event.
 func (t *Terminal) Event(ctx context.Context) terminalapi.Event {
-	ev, err := t.events.Pull(ctx)
-	if err != nil {
-		return terminalapi.NewErrorf("unable to pull the next event: %v", err)
+	ev := t.events.Pull(ctx)
+	if ev == nil {
+		return terminalapi.NewError("unable to pull the next event")
 	}
 	return ev
 }