Pluggable Monitors: Improved error logging / fixed resource leak in some rare conditions (#1638)

* Improve error logging for pluggable monitor

* Force quit of pluggable monitor if the port open fails

Author: cmaglie

arduino/monitor/monitor.go

@@ -111,7 +111,7 @@ func (mon *PluggableMonitor) jsonDecodeLoop(in io.Reader, outChan chan<- *monito
 		if err := decoder.Decode(&msg); err != nil {
 			mon.incomingMessagesError = err
 			close(outChan)
-			mon.log.Errorf("stopped decode loop")
+			mon.log.Errorf("stopped decode loop: %s", err)
 			return
 		}
 		mon.log.

commands/monitor/monitor.go

@@ -28,6 +28,7 @@ import (
 	"github.com/arduino/arduino-cli/i18n"
 	rpc "github.com/arduino/arduino-cli/rpc/cc/arduino/cli/commands/v1"
 	"github.com/arduino/go-properties-orderedmap"
+	"github.com/sirupsen/logrus"
 )
 
 var tr = i18n.Tr
@@ -76,18 +77,23 @@ func Monitor(ctx context.Context, req *rpc.MonitorRequest) (*PortProxy, *pluggab
 
 	descriptor, err := m.Describe()
 	if err != nil {
+		m.Quit()
 		return nil, nil, &arduino.FailedMonitorError{Cause: err}
 	}
 
 	monIO, err := m.Open(req.GetPort().GetAddress(), req.GetPort().GetProtocol())
 	if err != nil {
+		m.Quit()
 		return nil, nil, &arduino.FailedMonitorError{Cause: err}
 	}
 
 	for _, setting := range req.GetPortConfiguration().Settings {
-		m.Configure(setting.SettingId, setting.Value)
+		if err := m.Configure(setting.SettingId, setting.Value); err != nil {
+			logrus.Errorf("Could not set configuration %s=%s: %s", setting.SettingId, setting.Value, err)
+		}
 	}
 
+	logrus.Infof("Port %s successfully opened", req.GetPort().GetAddress())
 	return &PortProxy{
 		rw:               monIO,
 		changeSettingsCB: m.Configure,