ensure folder when file writer rotating

file.go

@@ -2,6 +2,7 @@ package log
 
 import (
 	"crypto/md5"
+	"errors"
 	"io"
 	"os"
 	"path/filepath"
@@ -155,7 +156,14 @@ func (w *FileWriter) rotate() (err error) {
 	var file *os.File
 	file, err = os.OpenFile(w.fileargs(timeNow()))
 	if err != nil {
-		return err
+		if errors.Is(err, os.ErrNotExist) && w.EnsureFolder {
+			if err = os.MkdirAll(filepath.Dir(w.Filename), 0755); err == nil {
+				file, err = os.OpenFile(w.fileargs(timeNow()))
+			}
+		}
+		if err != nil {
+			return err
+		}
 	}
 	if w.file != nil {
 		w.file.Close()

file_test.go

@@ -98,6 +98,18 @@ func TestFileWriterEnsureFolder(t *testing.T) {
 		t.Logf("file writer return error: %+v", err)
 	}
 
+	remove(filepath.Dir(filename))
+
+	_, err = fmt.Fprint(w, text1)
+	if err != nil {
+		t.Logf("file writer return error: %+v", err)
+	}
+
+	err = w.Rotate()
+	if err != nil {
+		t.Logf("file writer rotate error: %+v", err)
+	}
+
 	_, err = fmt.Fprint(w, text2)
 	if err != nil {
 		t.Logf("file writer return error: %+v", err)