Fix serializer with empty string

schema/serializer.go

@@ -88,7 +88,9 @@ func (JSONSerializer) Scan(ctx context.Context, field *Field, dst reflect.Value,
 			return fmt.Errorf("failed to unmarshal JSONB value: %#v", dbValue)
 		}
 
-		err = json.Unmarshal(bytes, fieldValue.Interface())
+		if len(bytes) > 0 {
+			err = json.Unmarshal(bytes, fieldValue.Interface())
+		}
 	}
 
 	field.ReflectValueOf(ctx, dst).Set(fieldValue.Elem())
@@ -142,8 +144,10 @@ func (GobSerializer) Scan(ctx context.Context, field *Field, dst reflect.Value,
 		default:
 			return fmt.Errorf("failed to unmarshal gob value: %#v", dbValue)
 		}
-		decoder := gob.NewDecoder(bytes.NewBuffer(bytesValue))
-		err = decoder.Decode(fieldValue.Interface())
+		if len(bytesValue) > 0 {
+			decoder := gob.NewDecoder(bytes.NewBuffer(bytesValue))
+			err = decoder.Decode(fieldValue.Interface())
+		}
 	}
 	field.ReflectValueOf(ctx, dst).Set(fieldValue.Elem())
 	return

tests/go.mod

@@ -10,11 +10,11 @@ require (
 	github.com/lib/pq v1.10.6
 	github.com/mattn/go-sqlite3 v1.14.14 // indirect
 	golang.org/x/crypto v0.0.0-20220622213112-05595931fe9d // indirect
-	gorm.io/driver/mysql v1.3.4
+	gorm.io/driver/mysql v1.3.5
 	gorm.io/driver/postgres v1.3.8
 	gorm.io/driver/sqlite v1.3.6
 	gorm.io/driver/sqlserver v1.3.2
-	gorm.io/gorm v1.23.7
+	gorm.io/gorm v1.23.8
 )
 
 replace gorm.io/gorm => ../

tests/serializer_test.go

@@ -113,6 +113,14 @@ func TestSerializer(t *testing.T) {
 	}
 
 	AssertEqual(t, result, data)
+
+	if err := DB.Model(&result).Update("roles", "").Error; err != nil {
+		t.Fatalf("failed to update data's roles, got error %v", err)
+	}
+
+	if err := DB.First(&result, data.ID).Error; err != nil {
+		t.Fatalf("failed to query data, got error %v", err)
+	}
 }
 
 func TestSerializerAssignFirstOrCreate(t *testing.T) {