fix: reset null value in slice

scan.go

@@ -66,18 +66,23 @@ func (db *DB) scanIntoStruct(rows Rows, reflectValue reflect.Value, values []int
 	db.RowsAffected++
 	db.AddError(rows.Scan(values...))
 
+	joinedSchemaMap := make(map[*schema.Field]interface{}, 0)
 	for idx, field := range fields {
 		if field != nil {
 			if len(joinFields) == 0 || joinFields[idx][0] == nil {
 				db.AddError(field.Set(db.Statement.Context, reflectValue, values[idx]))
 			} else {
-				relValue := joinFields[idx][0].ReflectValueOf(db.Statement.Context, reflectValue)
-				if relValue.Kind() == reflect.Ptr && relValue.IsNil() {
-					if value := reflect.ValueOf(values[idx]).Elem(); value.Kind() == reflect.Ptr && value.IsNil() {
-						continue
-					}
+				joinSchema := joinFields[idx][0]
+				relValue := joinSchema.ReflectValueOf(db.Statement.Context, reflectValue)
+				if relValue.Kind() == reflect.Ptr {
+					if _, ok := joinedSchemaMap[joinSchema]; !ok {
+						if value := reflect.ValueOf(values[idx]).Elem(); value.Kind() == reflect.Ptr && value.IsNil() {
+							continue
+						}
 
-					relValue.Set(reflect.New(relValue.Type().Elem()))
+						relValue.Set(reflect.New(relValue.Type().Elem()))
+						joinedSchemaMap[joinSchema] = nil
+					}
 				}
 				db.AddError(joinFields[idx][1].Set(db.Statement.Context, relValue, values[idx]))
 			}

schema/field.go

@@ -587,6 +587,8 @@ func (field *Field) setupValuerAndSetter() {
 			case **bool:
 				if data != nil && *data != nil {
 					field.ReflectValueOf(ctx, value).SetBool(**data)
+				} else {
+					field.ReflectValueOf(ctx, value).SetBool(false)
 				}
 			case bool:
 				field.ReflectValueOf(ctx, value).SetBool(data)
@@ -606,6 +608,8 @@ func (field *Field) setupValuerAndSetter() {
 			case **int64:
 				if data != nil && *data != nil {
 					field.ReflectValueOf(ctx, value).SetInt(**data)
+				} else {
+					field.ReflectValueOf(ctx, value).SetInt(0)
 				}
 			case int64:
 				field.ReflectValueOf(ctx, value).SetInt(data)
@@ -670,6 +674,8 @@ func (field *Field) setupValuerAndSetter() {
 			case **uint64:
 				if data != nil && *data != nil {
 					field.ReflectValueOf(ctx, value).SetUint(**data)
+				} else {
+					field.ReflectValueOf(ctx, value).SetUint(0)
 				}
 			case uint64:
 				field.ReflectValueOf(ctx, value).SetUint(data)
@@ -722,6 +728,8 @@ func (field *Field) setupValuerAndSetter() {
 			case **float64:
 				if data != nil && *data != nil {
 					field.ReflectValueOf(ctx, value).SetFloat(**data)
+				} else {
+					field.ReflectValueOf(ctx, value).SetFloat(0)
 				}
 			case float64:
 				field.ReflectValueOf(ctx, value).SetFloat(data)
@@ -766,6 +774,8 @@ func (field *Field) setupValuerAndSetter() {
 			case **string:
 				if data != nil && *data != nil {
 					field.ReflectValueOf(ctx, value).SetString(**data)
+				} else {
+					field.ReflectValueOf(ctx, value).SetString("")
 				}
 			case string:
 				field.ReflectValueOf(ctx, value).SetString(data)

tests/query_test.go

@@ -1258,3 +1258,80 @@ func TestQueryScannerWithSingleColumn(t *testing.T) {
 
 	AssertEqual(t, result2.data, 20)
 }
+
+func TestQueryResetNullValue(t *testing.T) {
+	type QueryResetItem struct {
+		ID   string `gorm:"type:varchar(5)"`
+		Name string
+	}
+
+	type QueryResetNullValue struct {
+		ID      int
+		Name    string     `gorm:"default:NULL"`
+		Flag    bool       `gorm:"default:NULL"`
+		Number1 int64      `gorm:"default:NULL"`
+		Number2 uint64     `gorm:"default:NULL"`
+		Number3 float64    `gorm:"default:NULL"`
+		Now     *time.Time `gorm:"defalut:NULL"`
+		Item1Id string
+		Item1   *QueryResetItem `gorm:"references:ID"`
+		Item2Id string
+		Item2   *QueryResetItem `gorm:"references:ID"`
+	}
+
+	DB.Migrator().DropTable(&QueryResetNullValue{}, &QueryResetItem{})
+	DB.AutoMigrate(&QueryResetNullValue{}, &QueryResetItem{})
+
+	now := time.Now()
+	q1 := QueryResetNullValue{
+		Name:    "name",
+		Flag:    true,
+		Number1: 100,
+		Number2: 200,
+		Number3: 300.1,
+		Now:     &now,
+		Item1: &QueryResetItem{
+			ID:   "u_1_1",
+			Name: "item_1_1",
+		},
+		Item2: &QueryResetItem{
+			ID:   "u_1_2",
+			Name: "item_1_2",
+		},
+	}
+
+	q2 := QueryResetNullValue{
+		Item1: &QueryResetItem{
+			ID:   "u_2_1",
+			Name: "item_2_1",
+		},
+		Item2: &QueryResetItem{
+			ID:   "u_2_2",
+			Name: "item_2_2",
+		},
+	}
+
+	var err error
+	err = DB.Create(&q1).Error
+	if err != nil {
+		t.Errorf("failed to create:%v", err)
+	}
+
+	err = DB.Create(&q2).Error
+	if err != nil {
+		t.Errorf("failed to create:%v", err)
+	}
+
+	var qs []QueryResetNullValue
+	err = DB.Joins("Item1").Joins("Item2").Find(&qs).Error
+	if err != nil {
+		t.Errorf("failed to find:%v", err)
+	}
+
+	if len(qs) != 2 {
+		t.Fatalf("find count not equal:%d", len(qs))
+	}
+
+	AssertEqual(t, q1, qs[0])
+	AssertEqual(t, q2, qs[1])
+}