【FIX】Fix the issue where conversion fails when converting from sql.NullXXX types to basic types when selecting deepCopy option.

[jiang4869]

Problem Description

type User struct {
	Phone sql.NullString `json:"phone"`
}

func main() {
	phone := "12122255555"
	a := struct {
		Phone string `json:"phone"`
	}{
		Phone: phone,
	}
	u := &User{}
	err := copier.CopyWithOption(&u, a, copier.Option{DeepCopy: true, IgnoreEmpty: true})
	fmt.Println(err)
	fmt.Println(a)
	fmt.Println(u)
}

output

<nil>
{12122255555}
&{{ false}} 

The value of a.Phone was not copied to user.Phone, which is obviously not expected.

Solution

After verification, this is because the deepCopy option was added. Because when deepCopy is added, the following code is executed first. Since sql.NullXXX types are structures, the code returns directly. Although custom conversion can be used to solve this problem, it is not very elegant.

		if deepCopy {
			toKind := to.Kind()
			if toKind == reflect.Interface && to.IsNil() {
				if reflect.TypeOf(from.Interface()) != nil {
					to.Set(reflect.New(reflect.TypeOf(from.Interface())).Elem())
					toKind = reflect.TypeOf(to.Interface()).Kind()
				}
			}
			if from.Kind() == reflect.Ptr && from.IsNil() {
				return true
			}
			if toKind == reflect.Struct || toKind == reflect.Map || toKind == reflect.Slice {
				return false
			}
		}

Therefore, when judging whether it is a structure, exclude sql.NullXXX types first.

	if _, ok := to.Addr().Interface().(sql.Scanner); !ok && (toKind == reflect.Struct || toKind == reflect.Map || toKind == reflect.Slice) {
			return false, nil
		}

After the modification, the output of the above code is as follows. I have also added a unit test to ensure the correctness of other types.

<nil>
{12122255555}        
&{{12122255555 true}}

[jiang4869]

@jinzhu 能看下这个pr吗？