fix: wrong way of Unmarshal (#4397)

core/mapping/unmarshaler.go

@@ -2,6 +2,7 @@ package mapping
 
 import (
 	"encoding"
+	"encoding/base64"
 	"encoding/json"
 	"errors"
 	"fmt"
@@ -609,6 +610,19 @@ func (u *Unmarshaler) processFieldNotFromString(fieldType reflect.Type, value re
 	case valueKind == reflect.String && typeKind == reflect.Map:
 		return u.fillMapFromString(value, mapValue)
 	case valueKind == reflect.String && typeKind == reflect.Slice:
+		// try to find out if it's a byte slice, golang use []byte Marshal to base64 but there only SliceOf uint8/bytes can convert to []byte
+		// more details https://pkg.go.dev/encoding/json#Marshal
+		//> Array and slice values encode as JSON arrays, except that []byte encodes as a base64-encoded string, and a nil slice encodes as the null JSON value.
+		//and also u can find this https://stackoverflow.com/questions/34089750/marshal-byte-to-json-giving-a-strange-string
+		if fieldType.Elem().Kind() == reflect.Uint8 {
+			strVal := mapValue.(string)
+			decodedBytes, err := base64.StdEncoding.DecodeString(strVal)
+			// if err !=nil do next
+			if err == nil {
+				value.Set(reflect.ValueOf(decodedBytes))
+				return nil
+			}
+		}
 		return u.fillSliceFromString(fieldType, value, mapValue, fullName)
 	case valueKind == reflect.String && derefedFieldType == durationType:
 		return fillDurationValue(fieldType, value, mapValue.(string))

core/mapping/unmarshaler_test.go

@@ -4,6 +4,7 @@ import (
 	"encoding/json"
 	"errors"
 	"fmt"
+	"github.com/zeromicro/go-zero/core/jsonx"
 	"reflect"
 	"strconv"
 	"strings"
@@ -4868,14 +4869,27 @@ func TestUnmarshal_EnvWithOptionsWrongValueString(t *testing.T) {
 
 func TestUnmarshalJsonReaderMultiArray(t *testing.T) {
 	t.Run("reader multi array", func(t *testing.T) {
-		var res struct {
+		type testRes struct {
 			A string     `json:"a"`
 			B [][]string `json:"b"`
+			C []byte     `json:"c"`
 		}
-		payload := `{"a": "133", "b": [["add", "cccd"], ["eeee"]]}`
+		var res testRes
+		marshal := testRes{
+			A: "133",
+			B: [][]string{
+				{"add", "cccd"},
+				{"eeee"},
+			},
+			C: []byte("11122344wsss"),
+		}
+		bytes, err := jsonx.Marshal(marshal)
+		assert.NoError(t, err)
+		payload := string(bytes)
 		reader := strings.NewReader(payload)
 		if assert.NoError(t, UnmarshalJsonReader(reader, &res)) {
 			assert.Equal(t, 2, len(res.B))
+			assert.Equal(t, string(marshal.C), string(res.C))
 		}
 	})