Fix some issues with board list watcher

Author: silvanocerza

arduino/discovery/discoverymanager/discoverymanager.go

@@ -106,6 +106,22 @@ func (dm *DiscoveryManager) StopAll() error {
 	return nil
 }
 
+// QuitAll quits all the discoveries managed by this DiscoveryManager.
+// Returns the first error it meets or nil
+func (dm *DiscoveryManager) QuitAll() error {
+	for _, d := range dm.discoveries {
+		err := d.Quit()
+		if err != nil {
+			return err
+		}
+	}
+	if dm.globalEventCh != nil {
+		close(dm.globalEventCh)
+		dm.globalEventCh = nil
+	}
+	return nil
+}
+
 func (dm *DiscoveryManager) List() []*discovery.Port {
 	res := []*discovery.Port{}
 	for _, disc := range dm.discoveries {

commands/board/list.go

@@ -237,6 +237,7 @@ func Watch(instanceID int32, interrupt <-chan bool) (<-chan *rpc.BoardListWatchR
 	outChan := make(chan *rpc.BoardListWatchResponse)
 
 	go func() {
+		defer close(outChan)
 		for _, err := range errs {
 			outChan <- &rpc.BoardListWatchResponse{
 				EventType: "error",
@@ -272,6 +273,16 @@ func Watch(instanceID int32, interrupt <-chan bool) (<-chan *rpc.BoardListWatchR
 					Error:     boardsError,
 				}
 			case <-interrupt:
+				err := pm.DiscoveryManager().QuitAll()
+				if err != nil {
+					outChan <- &rpc.BoardListWatchResponse{
+						EventType: "error",
+						Error:     err.Error(),
+					}
+					// Don't close the channel if quitting all discoveries
+					// failed, otherwise some processes might be left running.
+					continue
+				}
 				return
 			}
 		}