防止结构初始化中丢失字段

Question

Consider this example. Let's say I have this object which is ubiquitous throughout my codebase:

type Person struct {
    Name string
    Age  int
    [some other fields]
}

Somewhere deep in the codebase, I also have some code that creates a new Person struct. Maybe it's something like the following utility function:

func copyPerson(origPerson Person) *Person {
    copy := Person{
        Name: origPerson.Name,
        Age:  origPerson.Age,
        [some other fields]
    }
    return &copy
}

Another developer comes along and adds a new field Gender to the Person struct. However, because the copyPerson function is in a distant piece of code they forget to update copyPerson. Since golang doesn't throw any warning or error if you omit a parameter when creating a struct, the code will compile and appear to work fine; the only difference is that the copyPerson method will now fail to copy over the Gender struct, and the result of copyPerson will have Gender replaced with a nil value (e.g. the empty string).

What is the best way to prevent this from happening? Is there a way to ask golang to enforce no missing parameters in a specific struct initialization? Is there a linter that can detect this type of potential error?

Answer 1

The best solution I have been able to come up with (and it's not very good) is to define a new struct tempPerson identical to the Person struct and put it nearby to any code which initializes a new Person struct, and to change the code that initializes a Person so that it instead initializes it as a tempPerson but then casts it to a Person. Like this:

type tempPerson struct {
    Name string
    Age  int
    [some other fields]
}

func copyPerson(origPerson Person) *Person {
    tempCopy := tempPerson{
        Name: orig.Name,
        Age:  orig.Age,
        [some other fields]
    }
    copy := (Person)(tempCopy)
    return &copy
}

This way if another field Gender is added to Person but not to tempPerson the code will fail at compile-time. Presumably the developer would then see the error, edit tempPerson to match their change to Person, and in doing so notice the nearby code which uses tempPerson and recognize that they should edit that code to also handle the Gender field as well.

I don't love this solution because it involves copying and pasting the struct definition everywhere that we initialize a Person struct and would like to have this safety. Is there any better way?