fix no imports

Signed-off-by: Loong Dai <loong.dai@intel.com>

pkg/gci/gci.go

@@ -2,6 +2,7 @@ package gci
 
 import (
 	"bytes"
+	"errors"
 	"fmt"
 	"os"
 	"sort"
@@ -123,6 +124,9 @@ func LoadFormatGoFile(file io.FileObj, cfg config.Config) (src, dist []byte, err
 
 	imports, headEnd, tailStart, tailEnd, err := parse.ParseFile(src)
 	if err != nil {
+		if errors.Is(err, parse.NoImportError{}) {
+			return src, src, nil
+		}
 		return nil, nil, err
 	}
 

pkg/parse/parse.go

@@ -73,6 +73,10 @@ func ParseFile(src []byte) (ImportList, int, int, int, error) {
 		return nil, 0, 0, 0, err
 	}
 
+	if len(f.Imports) == 0 {
+		return nil, 0, 0, 0, NoImportError{}
+	}
+
 	var data ImportList
 	for _, imp := range f.Imports {
 		start, end, name := getImports(imp)
@@ -113,3 +117,14 @@ func IsGeneratedFileByComment(in string) bool {
 
 	return false
 }
+
+type NoImportError struct{}
+
+func (n NoImportError) Error() string {
+	return "No imports"
+}
+
+func (i NoImportError) Is(err error) bool {
+	_, ok := err.(NoImportError)
+	return ok
+}