Fix Ls2JsonWriter

by allowing more spaces in the ls response.
by sending the error response of the list file system route only when no content has been written.

internal/runner/nomad_runner.go

@@ -134,15 +134,17 @@ func (r *NomadJob) ListFileSystem(
 	defer ls2json.Close()
 	retrieveCommand := (&dto.ExecutionRequest{Command: fmt.Sprintf("%s %q", command, path)}).FullCommand()
 	exitCode, err := r.api.ExecuteCommand(r.id, ctx, retrieveCommand, false, privilegedExecution,
-		&nullio.Reader{}, ls2json, io.Discard)
-	if err != nil {
-		return fmt.Errorf("%w: nomad error during retrieve file headers: %v",
+		&nullio.Reader{Ctx: ctx}, ls2json, io.Discard)
+	switch {
+	case ls2json.HasStartedWriting():
+		err = nil
+	case err != nil:
+		err = fmt.Errorf("%w: nomad error during retrieve file headers: %v",
 			nomad.ErrorExecutorCommunicationFailed, err)
+	case exitCode != 0:
+		err = ErrFileNotFound
 	}
-	if exitCode != 0 {
-		return ErrFileNotFound
-	}
-	return nil
+	return err
 }
 
 func (r *NomadJob) UpdateFileSystem(copyRequest *dto.UpdateFileSystemRequest) error {
@@ -188,7 +190,7 @@ func (r *NomadJob) GetFileContent(
 	}).FullCommand()
 	// Improve: Instead of using io.Discard use a **fixed-sized** buffer. With that we could improve the error message.
 	exitCode, err := r.api.ExecuteCommand(r.id, ctx, retrieveCommand, false, privilegedExecution,
-		&nullio.Reader{}, contentLengthWriter, io.Discard)
+		&nullio.Reader{Ctx: ctx}, contentLengthWriter, io.Discard)
 
 	if err != nil {
 		return fmt.Errorf("%w: nomad error during retrieve file content copy: %v",

pkg/nullio/ls2json.go

@@ -15,7 +15,8 @@ import (
 var (
 	log             = logging.GetLogger("nullio")
 	pathLineRegex   = regexp.MustCompile(`(.*):$`)
-	headerLineRegex = regexp.MustCompile(`([-aAbcCdDlMnpPsw?])([-rwxXsStT]{9})([+ ])\d+ (.+?) (.+?) +(\d+) (\d+) (.*)$`)
+	headerLineRegex = regexp.
+			MustCompile(`([-aAbcCdDlMnpPsw?])([-rwxXsStT]{9})(\+?) +\d+ +(.+?) +(.+?) +(\d+) +(\d+) +(.*)$`)
 )
 
 const (
@@ -39,6 +40,10 @@ type Ls2JsonWriter struct {
 	latestPath     []byte
 }
 
+func (w *Ls2JsonWriter) HasStartedWriting() bool {
+	return w.jsonStartSent
+}
+
 func (w *Ls2JsonWriter) Write(p []byte) (int, error) {
 	i, err := w.initializeJSONObject()
 	if err != nil {