From 8039ba0eb103b21cfd285fc8f4af855159c8507b Mon Sep 17 00:00:00 2001
From: a631807682 <631807682@qq.com>
Date: Mon, 13 Jun 2022 13:32:08 +0800
Subject: [PATCH] fix: can not set field in-place in join

---
 scan.go             | 17 +++++++++++------
 tests/query_test.go | 34 ++++++++++++++++++++++++++++++----
 2 files changed, 41 insertions(+), 10 deletions(-)

diff --git a/scan.go b/scan.go
index 1bb51560..6250fb57 100644
--- a/scan.go
+++ b/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]))
 			}
diff --git a/tests/query_test.go b/tests/query_test.go
index e0ee1c95..253d8409 100644
--- a/tests/query_test.go
+++ b/tests/query_test.go
@@ -1260,6 +1260,11 @@ func TestQueryScannerWithSingleColumn(t *testing.T) {
 }
 
 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"`
@@ -1268,10 +1273,14 @@ func TestQueryResetNullValue(t *testing.T) {
 		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{})
-	DB.AutoMigrate(&QueryResetNullValue{})
+	DB.Migrator().DropTable(&QueryResetNullValue{}, &QueryResetItem{})
+	DB.AutoMigrate(&QueryResetNullValue{}, &QueryResetItem{})
 
 	now := time.Now()
 	q1 := QueryResetNullValue{
@@ -1281,9 +1290,26 @@ func TestQueryResetNullValue(t *testing.T) {
 		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{}
+	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
@@ -1297,7 +1323,7 @@ func TestQueryResetNullValue(t *testing.T) {
 	}
 
 	var qs []QueryResetNullValue
-	err = DB.Find(&qs).Error
+	err = DB.Joins("Item1").Joins("Item2").Find(&qs).Error
 	if err != nil {
 		t.Errorf("failed to find:%v", err)
 	}