Save as NULL for nil object serialized into json

schema/serializer.go

@@ -100,6 +100,9 @@ func (JSONSerializer) Scan(ctx context.Context, field *Field, dst reflect.Value,
 // Value implements serializer interface
 func (JSONSerializer) Value(ctx context.Context, field *Field, dst reflect.Value, fieldValue interface{}) (interface{}, error) {
 	result, err := json.Marshal(fieldValue)
+	if string(result) == "null" {
+		return nil, err
+	}
 	return string(result), err
 }
 

tests/go.mod

@@ -7,10 +7,10 @@ require (
 	github.com/jinzhu/now v1.1.5
 	github.com/lib/pq v1.10.7
 	golang.org/x/crypto v0.0.0-20221012134737-56aed061732a // indirect
-	golang.org/x/text v0.3.8 // indirect
+	golang.org/x/text v0.4.0 // indirect
 	gorm.io/driver/mysql v1.4.3
 	gorm.io/driver/postgres v1.4.4
-	gorm.io/driver/sqlite v1.4.2
+	gorm.io/driver/sqlite v1.4.3
 	gorm.io/driver/sqlserver v1.4.1
 	gorm.io/gorm v1.24.0
 )

tests/serializer_test.go

@@ -18,6 +18,7 @@ type SerializerStruct struct {
 	gorm.Model
 	Name                   []byte                 `gorm:"json"`
 	Roles                  Roles                  `gorm:"serializer:json"`
+	Roles2                 *Roles                 `gorm:"serializer:json"`
 	Contracts              map[string]interface{} `gorm:"serializer:json"`
 	JobInfo                Job                    `gorm:"type:bytes;serializer:gob"`
 	CreatedTime            int64                  `gorm:"serializer:unixtime;type:time"` // store time in db, use int as field type
@@ -108,7 +109,7 @@ func TestSerializer(t *testing.T) {
 	}
 
 	var result SerializerStruct
-	if err := DB.First(&result, data.ID).Error; err != nil {
+	if err := DB.Where("roles2 IS NULL").First(&result, data.ID).Error; err != nil {
 		t.Fatalf("failed to query data, got error %v", err)
 	}