fix: mapping FillDefault is optional! bug (#3940)

core/mapping/unmarshaler.go

@@ -428,6 +428,10 @@ func (u *Unmarshaler) parseOptionsWithContext(field reflect.StructField, m Value
 		}
 	}
 
+	if u.opts.fillDefault {
+		return key, &options.fieldOptionsWithContext, nil
+	}
+
 	optsWithContext, err := options.toOptionsWithContext(key, m, fullName)
 	if err != nil {
 		return "", nil, err

core/mapping/unmarshaler_test.go

@@ -12,6 +12,7 @@ import (
 
 	"github.com/google/uuid"
 	"github.com/stretchr/testify/assert"
+
 	"github.com/zeromicro/go-zero/core/stringx"
 )
 
@@ -5411,6 +5412,16 @@ func TestFillDefaultUnmarshal(t *testing.T) {
 		assert.Equal(t, "c", st.C)
 	})
 
+	t.Run("optional !", func(t *testing.T) {
+		type St struct {
+			A string `json:",optional"`
+			B string `json:",optional=!A"`
+		}
+		var st = St{}
+		err := fillDefaultUnmarshal.Unmarshal(map[string]any{}, &st)
+		assert.NoError(t, err)
+	})
+
 	t.Run("has value", func(t *testing.T) {
 		type St struct {
 			A string `json:",default=a"`