Before returning from upload, check if the port is still alive

Now the upload detects cases when the upload port is "unstable", i.e.
the port changes even if it shouldn't (because the wait_for_upload_port
property in boards.txt is set to false).

This change should make the upload process more resilient.

Author: cmaglie

Diff for: commands/upload/upload.go

@@ -381,20 +381,18 @@ func runProgramAction(pme *packagemanager.Explorer,
 	uploadCtx, uploadCompleted := context.WithCancel(context.Background())
 	defer uploadCompleted()
 
-	// By default do not return any new port but if there is an
-	// expected port change then run the detector.
-	updatedUploadPort := f.NewFuture[*discovery.Port]()
-	if uploadProperties.GetBoolean("upload.wait_for_upload_port") {
-		watcher, err := pme.DiscoveryManager().Watch()
-		if err != nil {
-			return nil, err
-		}
-		defer watcher.Close()
-
-		go detectUploadPort(uploadCtx, port, watcher.Feed(), updatedUploadPort)
-	} else {
-		updatedUploadPort.Send(nil)
+	// Start the upload port change detector.
+	watcher, err := pme.DiscoveryManager().Watch()
+	if err != nil {
+		return nil, err
 	}
+	defer watcher.Close()
+	updatedUploadPort := f.NewFuture[*discovery.Port]()
+	go detectUploadPort(
+		uploadCtx,
+		port, watcher.Feed(),
+		uploadProperties.GetBoolean("upload.wait_for_upload_port"),
+		updatedUploadPort)
 
 	// Force port wait to make easier to unbrick boards like the Arduino Leonardo, or similar with native USB,
 	// when a sketch causes a crash and the native USB serial port is lost.
@@ -514,18 +512,19 @@ func runProgramAction(pme *packagemanager.Explorer,
 	uploadCompleted()
 	logrus.Tracef("Upload successful")
 
-	updatedPort := updatedUploadPort.Await()
-	if updatedPort == nil {
-		return userPort, nil
-	}
-	return updatedPort.ToRPC(), nil
+	return updatedUploadPort.Await().ToRPC(), nil
 }
 
-func detectUploadPort(uploadCtx context.Context, uploadPort *discovery.Port, watch <-chan *discovery.Event, result f.Future[*discovery.Port]) {
+func detectUploadPort(
+	uploadCtx context.Context,
+	uploadPort *discovery.Port, watch <-chan *discovery.Event,
+	waitForUploadPort bool,
+	result f.Future[*discovery.Port],
+) {
 	log := logrus.WithField("task", "port_detection")
 	log.Tracef("Detecting new board port after upload")
 
-	var candidate *discovery.Port
+	candidate := uploadPort.Clone()
 	defer func() {
 		result.Send(candidate)
 	}()
@@ -538,7 +537,13 @@ func detectUploadPort(uploadCtx context.Context, uploadPort *discovery.Port, wat
 				log.Error("Upload port detection failed, watcher closed")
 				return
 			}
-			log.WithField("event", ev).Trace("Ignored watcher event before upload")
+			if candidate != nil && ev.Type == "remove" && ev.Port.Equals(candidate) {
+				log.WithField("event", ev).Trace("User-specified port has been disconnected, forcing waiting for upload port")
+				waitForUploadPort = true
+				candidate = nil
+			} else {
+				log.WithField("event", ev).Trace("Ignored watcher event before upload")
+			}
 			continue
 		case <-uploadCtx.Done():
 			// Upload completed, move to the next phase
@@ -549,19 +554,25 @@ func detectUploadPort(uploadCtx context.Context, uploadPort *discovery.Port, wat
 	// Pick the first port that is detected after the upload
 	desiredHwID := uploadPort.HardwareID
 	timeout := time.After(5 * time.Second)
+	if !waitForUploadPort {
+		timeout = time.After(time.Second)
+	}
 	for {
 		select {
 		case ev, ok := <-watch:
 			if !ok {
 				log.Error("Upload port detection failed, watcher closed")
 				return
 			}
-			if ev.Type == "remove" && candidate != nil {
-				if candidate.Equals(ev.Port) {
-					log.WithField("event", ev).Trace("Candidate port is no more available")
-					candidate = nil
-					continue
+			if candidate != nil && ev.Type == "remove" && candidate.Equals(ev.Port) {
+				log.WithField("event", ev).Trace("Candidate port is no more available")
+				candidate = nil
+				if !waitForUploadPort {
+					waitForUploadPort = true
+					timeout = time.After(5 * time.Second)
+					log.Trace("User-specified port has been disconnected, now waiting for upload port, timeout exteneded by 5 seconds")
 				}
+				continue
 			}
 			if ev.Type != "add" {
 				log.WithField("event", ev).Trace("Ignored non-add event")