Made the gRPC daemon actually wait for port close completion

Author: cmaglie

commands/daemon/daemon.go

@@ -20,6 +20,7 @@ import (
 	"errors"
 	"fmt"
 	"io"
+	"sync/atomic"
 
 	"github.com/arduino/arduino-cli/commands"
 	"github.com/arduino/arduino-cli/commands/board"
@@ -490,6 +491,10 @@ func (s *ArduinoCoreServerImpl) Monitor(stream rpc.ArduinoCoreService_MonitorSer
 	_ = syncSend.Send(&rpc.MonitorResponse{Success: true})
 
 	cancelCtx, cancel := context.WithCancel(stream.Context())
+	gracefulCloseInitiated := &atomic.Bool{}
+	gracefuleCloseCtx, gracefulCloseCancel := context.WithCancel(context.Background())
+
+	// gRPC stream receiver (gRPC data -> monitor, config, close)
 	go func() {
 		defer cancel()
 		for {
@@ -509,9 +514,11 @@ func (s *ArduinoCoreServerImpl) Monitor(stream rpc.ArduinoCoreService_MonitorSer
 				}
 			}
 			if closeMsg := msg.GetClose(); closeMsg {
+				gracefulCloseInitiated.Store(true)
 				if err := portProxy.Close(); err != nil {
 					logrus.WithError(err).Debug("Error closing monitor port")
 				}
+				gracefulCloseCancel()
 			}
 			tx := msg.GetTxData()
 			for len(tx) > 0 {
@@ -528,8 +535,9 @@ func (s *ArduinoCoreServerImpl) Monitor(stream rpc.ArduinoCoreService_MonitorSer
 		}
 	}()
 
+	// gRPC stream sender (monitor -> gRPC)
 	go func() {
-		defer cancel()
+		defer cancel() // unlock the receiver
 		buff := make([]byte, 4096)
 		for {
 			n, err := portProxy.Read(buff)
@@ -547,6 +555,11 @@ func (s *ArduinoCoreServerImpl) Monitor(stream rpc.ArduinoCoreService_MonitorSer
 	}()
 
 	<-cancelCtx.Done()
-	portProxy.Close()
+	if gracefulCloseInitiated.Load() {
+		// Port closing has been initiated in the receiver
+		<-gracefuleCloseCtx.Done()
+	} else {
+		portProxy.Close()
+	}
 	return nil
 }

internal/integrationtest/monitor/monitor_grpc_test.go

@@ -82,7 +82,7 @@ func TestMonitorGRPCClose(t *testing.T) {
 	}
 
 	// Now close the monitor using MonitorRequest_Close
-	for tries := 0; tries < 5; tries++ { // Try the test 5 times to avoid flukes
+	{
 		// Keep a timeout to allow the test to exit in any case
 		ctx, cancel := context.WithTimeout(context.Background(), time.Second*10)
 		mon, err := grpcInst.Monitor(ctx, ports[0].Port)

internal/mock_serial_monitor/main.go

@@ -197,7 +197,7 @@ func (d *SerialMonitor) Close() error {
 	d.mockedSerialPort.Close()
 	d.openedPort = false
 	if d.muxFile != nil {
-		time.Sleep(500 * time.Millisecond) // Emulate a small delay closing the port to check gRPC synchronization
+		time.Sleep(2000 * time.Millisecond) // Emulate a small delay closing the port to check gRPC synchronization
 		d.muxFile.Remove()
 		d.muxFile = nil
 	}