Fix create duplicated value when updating nested has many relationship,

close go-gorm#4796

callbacks/associations.go

@@ -7,6 +7,7 @@ import (
 	"gorm.io/gorm"
 	"gorm.io/gorm/clause"
 	"gorm.io/gorm/schema"
+	"gorm.io/gorm/utils"
 )
 
 func SaveBeforeAssociations(create bool) func(db *gorm.DB) {
@@ -182,6 +183,7 @@ func SaveAfterAssociations(create bool) func(db *gorm.DB) {
 					fieldType = reflect.PtrTo(fieldType)
 				}
 				elems := reflect.MakeSlice(reflect.SliceOf(fieldType), 0, 10)
+				identityMap := map[string]bool{}
 				appendToElems := func(v reflect.Value) {
 					if _, zero := rel.Field.ValueOf(v); !zero {
 						f := reflect.Indirect(rel.Field.ReflectValueOf(v))
@@ -197,10 +199,21 @@ func SaveAfterAssociations(create bool) func(db *gorm.DB) {
 								}
 							}
 
-							if isPtr {
-								elems = reflect.Append(elems, elem)
-							} else {
-								elems = reflect.Append(elems, elem.Addr())
+							relPrimaryValues := make([]interface{}, 0, len(rel.FieldSchema.PrimaryFields))
+							for _, pf := range rel.FieldSchema.PrimaryFields {
+								if pfv, ok := pf.ValueOf(elem); !ok {
+									relPrimaryValues = append(relPrimaryValues, pfv)
+								}
+							}
+
+							cacheKey := utils.ToStringKey(relPrimaryValues)
+							if len(relPrimaryValues) == 0 || (len(relPrimaryValues) == len(rel.FieldSchema.PrimaryFields) && !identityMap[cacheKey]) {
+								identityMap[cacheKey] = true
+								if isPtr {
+									elems = reflect.Append(elems, elem)
+								} else {
+									elems = reflect.Append(elems, elem.Addr())
+								}
 							}
 						}
 					}

tests/associations_test.go

@@ -178,19 +178,21 @@ func TestForeignKeyConstraintsBelongsTo(t *testing.T) {
 }
 
 func TestFullSaveAssociations(t *testing.T) {
+	coupon := &Coupon{
+		ID: "full-save-association-coupon1",
+		AppliesToProduct: []*CouponProduct{
+			{
+				CouponId:  "full-save-association-coupon1",
+				ProductId: "full-save-association-product1",
+			},
+		},
+		AmountOff:  10,
+		PercentOff: 0.0,
+	}
+
 	err := DB.
 		Session(&gorm.Session{FullSaveAssociations: true}).
-		Create(&Coupon{
-			ID: "full-save-association-coupon1",
-			AppliesToProduct: []*CouponProduct{
-				{
-					CouponId:  "full-save-association-coupon1",
-					ProductId: "full-save-association-product1",
-				},
-			},
-			AmountOff:  10,
-			PercentOff: 0.0,
-		}).Error
+		Create(coupon).Error
 
 	if err != nil {
 		t.Errorf("Failed, got error: %v", err)
@@ -203,4 +205,9 @@ func TestFullSaveAssociations(t *testing.T) {
 	if DB.First(&CouponProduct{}, "coupon_id = ? AND product_id = ?", "full-save-association-coupon1", "full-save-association-product1").Error != nil {
 		t.Errorf("Failed to query saved association")
 	}
+
+	orders := []Order{{Num: "order1", Coupon: coupon}, {Num: "order2", Coupon: coupon}}
+	if err := DB.Create(&orders).Error; err != nil {
+		t.Errorf("failed to create orders, got %v", err)
+	}
 }

tests/multi_primary_keys_test.go

@@ -427,7 +427,7 @@ func TestCompositePrimaryKeysAssociations(t *testing.T) {
 
 	DB.Migrator().DropTable(&Label{}, &Book{})
 	if err := DB.AutoMigrate(&Label{}, &Book{}); err != nil {
-		t.Fatalf("failed to migrate")
+		t.Fatalf("failed to migrate, got %v", err)
 	}
 
 	book := Book{

tests/tests_test.go

@@ -87,7 +87,7 @@ func OpenTestConnection() (db *gorm.DB, err error) {
 
 func RunMigrations() {
 	var err error
-	allModels := []interface{}{&User{}, &Account{}, &Pet{}, &Company{}, &Toy{}, &Language{}, &Coupon{}, &CouponProduct{}}
+	allModels := []interface{}{&User{}, &Account{}, &Pet{}, &Company{}, &Toy{}, &Language{}, &Coupon{}, &CouponProduct{}, &Order{}}
 	rand.Seed(time.Now().UnixNano())
 	rand.Shuffle(len(allModels), func(i, j int) { allModels[i], allModels[j] = allModels[j], allModels[i] })
 

utils/tests/models.go

@@ -72,3 +72,10 @@ type CouponProduct struct {
 	CouponId  string `gorm:"primarykey; size:255"`
 	ProductId string `gorm:"primarykey; size:255"`
 }
+
+type Order struct {
+	gorm.Model
+	Num      string
+	Coupon   *Coupon
+	CouponID string
+}