fix(command): fix rare race condition on log line stream at command completion

Author: qdm12

internal/command/start.go

@@ -21,7 +21,6 @@ func (c *Cmder) Start(cmd *exec.Cmd) (
 func start(cmd execCmd) (stdoutLines, stderrLines <-chan string,
 	waitError <-chan error, startErr error,
 ) {
-	stop := make(chan struct{})
 	stdoutReady := make(chan struct{})
 	stdoutLinesCh := make(chan string)
 	stdoutDone := make(chan struct{})
@@ -33,22 +32,20 @@ func start(cmd execCmd) (stdoutLines, stderrLines <-chan string,
 	if err != nil {
 		return nil, nil, nil, err
 	}
-	go streamToChannel(stdoutReady, stop, stdoutDone, stdout, stdoutLinesCh)
+	go streamToChannel(stdoutReady, stdoutDone, stdout, stdoutLinesCh)
 
 	stderr, err := cmd.StderrPipe()
 	if err != nil {
 		_ = stdout.Close()
-		close(stop)
 		<-stdoutDone
 		return nil, nil, nil, err
 	}
-	go streamToChannel(stderrReady, stop, stderrDone, stderr, stderrLinesCh)
+	go streamToChannel(stderrReady, stderrDone, stderr, stderrLinesCh)
 
 	err = cmd.Start()
 	if err != nil {
 		_ = stdout.Close()
 		_ = stderr.Close()
-		close(stop)
 		<-stdoutDone
 		<-stderrDone
 		return nil, nil, nil, err
@@ -57,19 +54,20 @@ func start(cmd execCmd) (stdoutLines, stderrLines <-chan string,
 	waitErrorCh := make(chan error)
 	go func() {
 		err := cmd.Wait()
-		_ = stdout.Close()
-		_ = stderr.Close()
-		close(stop)
 		<-stdoutDone
 		<-stderrDone
+		_ = stdout.Close()
+		_ = stderr.Close()
 		waitErrorCh <- err
 	}()
 
+	<-stdoutReady
+	<-stderrReady
+
 	return stdoutLinesCh, stderrLinesCh, waitErrorCh, nil
 }
 
-func streamToChannel(ready chan<- struct{},
-	stop <-chan struct{}, done chan<- struct{},
+func streamToChannel(ready chan<- struct{}, done chan<- struct{},
 	stream io.Reader, lines chan<- string,
 ) {
 	defer close(done)
@@ -89,12 +87,5 @@ func streamToChannel(ready chan<- struct{},
 	if err == nil || errors.Is(err, os.ErrClosed) {
 		return
 	}
-
-	// ignore the error if it is stopped.
-	select {
-	case <-stop:
-		return
-	default:
-		lines <- "stream error: " + err.Error()
-	}
+	lines <- "stream error: " + err.Error()
 }