Refactor preload error check

callbacks/query.go

@@ -186,6 +186,11 @@ func BuildQuerySQL(db *gorm.DB) {
 
 func Preload(db *gorm.DB) {
 	if db.Error == nil && len(db.Statement.Preloads) > 0 {
+		if db.Statement.Schema == nil {
+			db.AddError(fmt.Errorf("%w when using preload", gorm.ErrModelValueRequired))
+			return
+		}
+
 		preloadMap := map[string]map[string][]interface{}{}
 		for name := range db.Statement.Preloads {
 			preloadFields := strings.Split(name, ".")

finisher_api.go

@@ -369,10 +369,6 @@ func (db *DB) Delete(value interface{}, conds ...interface{}) (tx *DB) {
 
 func (db *DB) Count(count *int64) (tx *DB) {
 	tx = db.getInstance()
-	if len(tx.Statement.Preloads) > 0 {
-		tx.AddError(ErrPreloadNotAllowed)
-		return
-	}
 	if tx.Statement.Model == nil {
 		tx.Statement.Model = tx.Statement.Dest
 		defer func() {

tests/count_test.go

@@ -150,8 +150,16 @@ func TestCount(t *testing.T) {
 		Where("name in ?", []string{user1.Name, user2.Name, user3.Name}).
 		Preload("Toys", func(db *gorm.DB) *gorm.DB {
 			return db.Table("toys").Select("name")
-		}).Count(&count12).Error; err != gorm.ErrPreloadNotAllowed {
+		}).Count(&count12).Error; err == nil {
-		t.Errorf("should returns preload not allowed error, but got %v", err)
+		t.Errorf("error should raise when using preload without schema")
 	}
 
+	var count13 int64
+	if err := DB.Model(User{}).
+		Where("name in ?", []string{user1.Name, user2.Name, user3.Name}).
+		Preload("Toys", func(db *gorm.DB) *gorm.DB {
+			return db.Table("toys").Select("name")
+		}).Count(&count13).Error; err != nil {
+		t.Errorf("no error should raise when using count with preload, but got %v", err)
+	}
 }

tests/go.mod

@@ -9,7 +9,7 @@ require (
 	github.com/jinzhu/now v1.1.4
 	github.com/lib/pq v1.10.4
 	github.com/mattn/go-sqlite3 v1.14.12 // indirect
-	golang.org/x/crypto v0.0.0-20220214200702-86341886e292 // indirect
+	golang.org/x/crypto v0.0.0-20220315160706-3147a52a75dd // indirect
 	gorm.io/driver/mysql v1.3.2
 	gorm.io/driver/postgres v1.3.1
 	gorm.io/driver/sqlite v1.3.1