Optimize ParseByLayout method when the timezone is empty

parser.go

@@ -8,7 +8,7 @@ import (
 // Parse parses a standard time string as a Carbon instance.
 // 将标准格式时间字符串解析成 Carbon 实例
 func (c Carbon) Parse(value string, timezone ...string) Carbon {
-	if value == "" {
+	if len(value) == 0 {
 		c.Error = invalidValueError(value)
 		return c
 	}
@@ -65,9 +65,12 @@ func (c Carbon) ParseByLayout(value, layout string, timezone ...string) Carbon {
 	if c.Error != nil {
 		return c
 	}
-	if value == "" {
+	if len(value) == 0 {
 		return c
 	}
+	if len(layout) == 0 {
+		layout = defaultLayout
+	}
 	if layout == "timestamp" {
 		timestamp, _ := strconv.ParseInt(value, 10, 64)
 		return c.CreateFromTimestamp(timestamp)

parser_unit_test.go

@@ -1,6 +1,7 @@
 package carbon
 
 import (
+	"fmt"
 	"testing"
 
 	"github.com/stretchr/testify/assert"
@@ -223,6 +224,7 @@ func TestCarbon_Issue206(t *testing.T) {
 
 	for _, tt := range tests {
 		t.Run(tt.name, func(t *testing.T) {
+			fmt.Println("err", tt.carbon.Error)
 			assert.Equalf(t, tt.want, tt.carbon.ToString(PRC), "Parse()")
 		})
 	}