Implement failing testcase for relation id updates

db.go

@@ -84,7 +84,7 @@ func OpenTestConnection() (db *gorm.DB, err error) {
 
 func RunMigrations() {
 	var err error
-	allModels := []interface{}{&User{}, &Account{}, &Pet{}, &Company{}, &Toy{}, &Language{}}
+	allModels := []interface{}{&User{}}
 	rand.Seed(time.Now().UnixNano())
 	rand.Shuffle(len(allModels), func(i, j int) { allModels[i], allModels[j] = allModels[j], allModels[i] })
 

go.mod

@@ -9,7 +9,7 @@ require (
 	gorm.io/driver/postgres v1.6.0
 	gorm.io/driver/sqlite v1.6.0
 	gorm.io/driver/sqlserver v1.6.1
-	gorm.io/gorm v1.30.1
+	gorm.io/gorm v1.31.0
 )
 
 require (
@@ -20,22 +20,15 @@ require (
 	github.com/google/uuid v1.6.0 // indirect
 	github.com/jackc/pgpassfile v1.0.0 // indirect
 	github.com/jackc/pgservicefile v0.0.0-20240606120523-5a60cdf6a761 // indirect
-	github.com/jackc/pgx/v5 v5.7.5 // indirect
+	github.com/jackc/pgx/v5 v5.7.6 // indirect
 	github.com/jackc/puddle/v2 v2.2.2 // indirect
 	github.com/jinzhu/inflection v1.0.0 // indirect
 	github.com/jinzhu/now v1.1.5 // indirect
 	github.com/mattn/go-sqlite3 v1.14.32 // indirect
-	github.com/microsoft/go-mssqldb v1.9.2 // indirect
-	golang.org/x/crypto v0.41.0 // indirect
-	golang.org/x/exp v0.0.0-20250819193227-8b4c13bb791b // indirect
-	golang.org/x/mod v0.27.0 // indirect
-	golang.org/x/sync v0.16.0 // indirect
-	golang.org/x/text v0.28.0 // indirect
-	golang.org/x/tools v0.36.0 // indirect
-	gorm.io/cmd/gorm v0.1.1-0.20250825094947-30e7d4fa1f1f // indirect
-	gorm.io/datatypes v1.2.5 // indirect
-	gorm.io/hints v1.1.2 // indirect
-	gorm.io/plugin/dbresolver v1.6.0 // indirect
+	github.com/microsoft/go-mssqldb v1.9.3 // indirect
+	golang.org/x/crypto v0.43.0 // indirect
+	golang.org/x/sync v0.17.0 // indirect
+	golang.org/x/text v0.30.0 // indirect
 )
 
 replace gorm.io/gorm => ./gorm

main_test.go

@@ -11,25 +11,27 @@ import (
 // TEST_DRIVERS: sqlite, mysql, postgres, sqlserver
 
 func TestGORM(t *testing.T) {
-	user := models.User{Name: "jinzhu"}
+	acc := models.Account{Number: "foo"}
+	DB.Create(&acc)
+	acc2 := models.Account{Number: "baz"}
+	DB.Create(&acc2)
+
+	user := models.User{AccountId: &acc.ID, Name: "Bar"}
 
 	DB.Create(&user)
 
-	var result models.User
-	if err := DB.First(&result, user.ID).Error; err != nil {
-		t.Errorf("Failed, got error: %v", err)
-	}
-}
+	var user2 = models.User{}
+	DB.Preload("Account").Where(models.User{Name: "Bar"}).FirstOrInit(&user2)
 
-// func TestGORMGen(t *testing.T) {
-// 	user := models.User{Name: "jinzhu2"}
-// 	ctx := context.Background()
+	id_backup := acc2.ID
 
-// 	gorm.G[models.User](DB).Create(ctx, &user)
+	// This should update the AccountId to acc2.ID.
+	// However, when a relation was loaded before, this will actually reset back to acc.ID
+	// When using nullable fields like here, it will also overwrite the ID in acc2
+	user2.AccountId = &acc2.ID
+	DB.Save(&user2)
 
-// 	if u, err := gorm.G[models.User](DB).Where(g.User.ID.Eq(user.ID)).First(ctx); err != nil {
-// 		t.Errorf("Failed, got error: %v", err)
-// 	} else if u.Name != user.Name {
-// 		t.Errorf("Failed, got user name: %v", u.Name)
-// 	}
-// }
+	if  *user2.AccountId != id_backup {
+		t.Errorf("Account ID not properly saved: %v", *user2.AccountId)
+	}
+}

models/models.go

@@ -1,8 +1,8 @@
 package models
 
 import (
-	"database/sql"
-	"time"
+	// "database/sql"
+	// "time"
 
 	"gorm.io/gorm"
 )
@@ -13,48 +13,12 @@ import (
 // His pet also has one Toy (has one - polymorphic)
 type User struct {
 	gorm.Model
-	Name      string
-	Age       uint
-	Birthday  *time.Time
+	Name string
+	AccountId *uint
 	Account   Account
-	Pets      []*Pet
-	Toys      []Toy `gorm:"polymorphic:Owner"`
-	CompanyID *int
-	Company   Company
-	ManagerID *uint
-	Manager   *User
-	Team      []User     `gorm:"foreignkey:ManagerID"`
-	Languages []Language `gorm:"many2many:UserSpeak"`
-	Friends   []*User    `gorm:"many2many:user_friends"`
-	Active    bool
 }
 
 type Account struct {
 	gorm.Model
-	UserID sql.NullInt64
 	Number string
-}
-
-type Pet struct {
-	gorm.Model
-	UserID *uint
-	Name   string
-	Toy    Toy `gorm:"polymorphic:Owner;"`
-}
-
-type Toy struct {
-	gorm.Model
-	Name      string
-	OwnerID   string
-	OwnerType string
-}
-
-type Company struct {
-	ID   int
-	Name string
-}
-
-type Language struct {
-	Code string `gorm:"primarykey"`
-	Name string
-}
+}