imap: fix panic when sending multiple connect cmds

fixes the panic when the user sends multiple connect commands and is
already connected. The panic is caused by closing an already closed
channel. This happens when the idle re-init code is not executed, e.g.
when there's a return statement in the switch block.  A defer func()
before the switch block will prevent this. The existing behavior of only
creating a new idleStop channel when properly connected is preseverd.

Signed-off-by: Koni Marti <koni.marti@gmail.com>

worker/imap/worker.go

@@ -74,6 +74,14 @@ func (w *IMAPWorker) handleMessage(msg types.WorkerMessage) error {
 			w.worker.PostMessage(&types.Error{Error: err}, nil)
 		}
 	}
+	defer func() {
+		if w.client != nil && w.client.State() == imap.SelectedState {
+			w.idleStop = make(chan struct{})
+			go func() {
+				w.idleDone <- w.client.Idle(w.idleStop, &client.IdleOptions{0, 0})
+			}()
+		}
+	}()
 
 	var reterr error // will be returned at the end, needed to support idle
 
@@ -83,7 +91,8 @@ func (w *IMAPWorker) handleMessage(msg types.WorkerMessage) error {
 	case *types.Configure:
 		u, err := url.Parse(msg.Config.Source)
 		if err != nil {
-			return err
+			reterr = err
+			break
 		}
 
 		w.config.scheme = u.Scheme
@@ -123,44 +132,50 @@ func (w *IMAPWorker) handleMessage(msg types.WorkerMessage) error {
 			case "connection-timeout":
 				val, err := time.ParseDuration(value)
 				if err != nil || val < 0 {
-					return fmt.Errorf(
+					reterr = fmt.Errorf(
 						"invalid connection-timeout value %v: %v",
 						value, err)
+					break
 				}
 				w.config.connection_timeout = val
 			case "keepalive-period":
 				val, err := time.ParseDuration(value)
 				if err != nil || val < 0 {
-					return fmt.Errorf(
+					reterr = fmt.Errorf(
 						"invalid keepalive-period value %v: %v",
 						value, err)
+					break
 				}
 				w.config.keepalive_period = val
 			case "keepalive-probes":
 				val, err := strconv.Atoi(value)
 				if err != nil || val < 0 {
-					return fmt.Errorf(
+					reterr = fmt.Errorf(
 						"invalid keepalive-probes value %v: %v",
 						value, err)
+					break
 				}
 				w.config.keepalive_probes = val
 			case "keepalive-interval":
 				val, err := time.ParseDuration(value)
 				if err != nil || val < 0 {
-					return fmt.Errorf(
+					reterr = fmt.Errorf(
 						"invalid keepalive-interval value %v: %v",
 						value, err)
+					break
 				}
 				w.config.keepalive_interval = int(val.Seconds())
 			}
 		}
 	case *types.Connect:
 		if w.client != nil && w.client.State() == imap.SelectedState {
-			return fmt.Errorf("Already connected")
+			reterr = fmt.Errorf("Already connected")
+			break
 		}
 		c, err := w.connect()
 		if err != nil {
-			return err
+			reterr = err
+			break
 		}
 
 		c.Updates = w.updates
@@ -168,10 +183,12 @@ func (w *IMAPWorker) handleMessage(msg types.WorkerMessage) error {
 		w.worker.PostMessage(&types.Done{types.RespondTo(msg)}, nil)
 	case *types.Disconnect:
 		if w.client == nil || w.client.State() != imap.SelectedState {
-			return fmt.Errorf("Not connected")
+			reterr = fmt.Errorf("Not connected")
+			break
 		}
 		if err := w.client.Logout(); err != nil {
-			return err
+			reterr = err
+			break
 		}
 		w.worker.PostMessage(&types.Done{types.RespondTo(msg)}, nil)
 	case *types.ListDirectories:
@@ -208,12 +225,6 @@ func (w *IMAPWorker) handleMessage(msg types.WorkerMessage) error {
 		reterr = errUnsupported
 	}
 
-	if w.client != nil && w.client.State() == imap.SelectedState {
-		w.idleStop = make(chan struct{})
-		go func() {
-			w.idleDone <- w.client.Idle(w.idleStop, &client.IdleOptions{0, 0})
-		}()
-	}
 	return reterr
 }