feat: Convert SQL nulls to zero values (ConvertNullToZeroValues)

Makes it the default behavior to convert SQL null values to zero
values for model fields which are not pointers.

callbacks/create.go

@@ -159,6 +159,7 @@ func CreateWithReturning(db *gorm.DB) {
 								break
 							}
 
+							resetFields := map[int]*schema.Field{}
 							for idx, field := range fields {
 								fieldValue := field.ReflectValueOf(reflectValue)
 
@@ -172,22 +173,47 @@ func CreateWithReturning(db *gorm.DB) {
 									goto BEGIN
 								}
 
-								values[idx] = fieldValue.Addr().Interface()
+								if field.FieldType.Kind() == reflect.Ptr {
+									values[idx] = fieldValue.Addr().Interface()
+								} else {
+									reflectValue := reflect.New(reflect.PtrTo(field.FieldType))
+									reflectValue.Elem().Set(fieldValue.Addr())
+									values[idx] = reflectValue.Interface()
+									resetFields[idx] = field
+								}
 							}
 
 							db.RowsAffected++
 							if err := rows.Scan(values...); err != nil {
 								db.AddError(err)
 							}
+
+							for idx, field := range resetFields {
+								if v := reflect.ValueOf(values[idx]).Elem().Elem(); v.IsValid() {
+									field.ReflectValueOf(reflectValue).Set(v)
+								}
+							}
 						}
 					case reflect.Struct:
+						resetFields := map[int]*schema.Field{}
 						for idx, field := range fields {
-							values[idx] = field.ReflectValueOf(db.Statement.ReflectValue).Addr().Interface()
+							if field.FieldType.Kind() == reflect.Ptr {
+								values[idx] = field.ReflectValueOf(db.Statement.ReflectValue).Addr().Interface()
+							} else {
+								reflectValue := reflect.New(reflect.PtrTo(field.FieldType))
+								reflectValue.Elem().Set(field.ReflectValueOf(db.Statement.ReflectValue).Addr())
+								values[idx] = reflectValue.Interface()
+								resetFields[idx] = field
+							}
 						}
-
 						if rows.Next() {
 							db.RowsAffected++
 							db.AddError(rows.Scan(values...))
+							for idx, field := range resetFields {
+								if v := reflect.ValueOf(values[idx]).Elem().Elem(); v.IsValid() {
+									field.ReflectValueOf(db.Statement.ReflectValue).Set(v)
+								}
+							}
 						}
 					}
 				} else {

tests/gorm_test.go

@@ -0,0 +1,98 @@
+package tests_test
+
+import (
+	"gorm.io/gorm"
+	"gorm.io/gorm/callbacks"
+	"testing"
+)
+
+func TestReturningWithNullToZeroValues(t *testing.T) {
+	dialect := DB.Dialector.Name()
+	switch dialect {
+	case "mysql", "sqlserver":
+		// these dialects do not support the "returning" clause
+		return
+	default:
+		// This user struct will leverage the existing users table, but override
+		// the Name field to default to null.
+		type user struct {
+			gorm.Model
+			Name string `gorm:"default:null"`
+		}
+		u1 := user{}
+		c := DB.Callback().Create().Get("gorm:create")
+		t.Cleanup(func() {
+			DB.Callback().Create().Replace("gorm:create", c)
+		})
+		DB.Callback().Create().Replace("gorm:create", callbacks.Create(&callbacks.Config{WithReturning: true}))
+
+		if results := DB.Create(&u1); results.Error != nil {
+			t.Fatalf("errors happened on create: %v", results.Error)
+		} else if results.RowsAffected != 1 {
+			t.Fatalf("rows affected expects: %v, got %v", 1, results.RowsAffected)
+		} else if u1.ID == 0 {
+			t.Fatalf("ID expects : not equal 0, got %v", u1.ID)
+		}
+
+		got := user{}
+		results := DB.First(&got, "id = ?", u1.ID)
+		if results.Error != nil {
+			t.Fatalf("errors happened on first: %v", results.Error)
+		} else if results.RowsAffected != 1 {
+			t.Fatalf("rows affected expects: %v, got %v", 1, results.RowsAffected)
+		} else if got.ID != u1.ID {
+			t.Fatalf("first expects: %v, got %v", u1, got)
+		}
+
+		results = DB.Select("id, name").Find(&got)
+		if results.Error != nil {
+			t.Fatalf("errors happened on first: %v", results.Error)
+		} else if results.RowsAffected != 1 {
+			t.Fatalf("rows affected expects: %v, got %v", 1, results.RowsAffected)
+		} else if got.ID != u1.ID {
+			t.Fatalf("select expects: %v, got %v", u1, got)
+		}
+
+		u1.Name = "jinzhu"
+		if results := DB.Save(&u1); results.Error != nil {
+			t.Fatalf("errors happened on update: %v", results.Error)
+		} else if results.RowsAffected != 1 {
+			t.Fatalf("rows affected expects: %v, got %v", 1, results.RowsAffected)
+		}
+
+		u1 = user{} // important to reinitialize this before creating it again
+		u2 := user{}
+		db := DB.Session(&gorm.Session{CreateBatchSize: 10})
+
+		if results := db.Create([]*user{&u1, &u2}); results.Error != nil {
+			t.Fatalf("errors happened on create: %v", results.Error)
+		} else if results.RowsAffected != 2 {
+			t.Fatalf("rows affected expects: %v, got %v", 1, results.RowsAffected)
+		} else if u1.ID == 0 {
+			t.Fatalf("ID expects : not equal 0, got %v", u1.ID)
+		} else if u2.ID == 0 {
+			t.Fatalf("ID expects : not equal 0, got %v", u2.ID)
+		}
+
+		var gotUsers []user
+		results = DB.Where("id in (?, ?)", u1.ID, u2.ID).Order("id asc").Select("id, name").Find(&gotUsers)
+		if results.Error != nil {
+			t.Fatalf("errors happened on first: %v", results.Error)
+		} else if results.RowsAffected != 2 {
+			t.Fatalf("rows affected expects: %v, got %v", 2, results.RowsAffected)
+		} else if gotUsers[0].ID != u1.ID {
+			t.Fatalf("select expects: %v, got %v", u1.ID, gotUsers[0].ID)
+		} else if gotUsers[1].ID != u2.ID {
+			t.Fatalf("select expects: %v, got %v", u2.ID, gotUsers[1].ID)
+		}
+
+		u1.Name = "Jinzhu"
+		u2.Name = "Zhang"
+		if results := DB.Save([]*user{&u1, &u2}); results.Error != nil {
+			t.Fatalf("errors happened on update: %v", results.Error)
+		} else if results.RowsAffected != 2 {
+			t.Fatalf("rows affected expects: %v, got %v", 1, results.RowsAffected)
+		}
+
+	}
+}