Should JEP 468 derived withers be opt in?

[Adam Gent]

Apologies. I meant instance factory methods and not static methods on my previous message.

On Thu, Nov 7, 2024, at 9:28 AM, Adam Gent wrote:
> One concern I have with "Withers" is that they don't codify the need or 
> requirement of multiple fields to be set at the exact time.
>
> Currently folks are probably making static methods on records for 
> creation. After (ab)using records in our code base that is less 
> academic and more business we frequently have a time field.
>
> record Something(String name, Instant updateTime, ... other fields) {
>    static Something withName(String name, Instant updateTime) {
>     ...
>     }
>    // Other with methods always including updateTime.
> }
>
> I admit my example is poor but the idea is that we want to encodify 
> that the time needs to be set on each call.
>
> If JEP 468 comes through one could create the record without specifying 
> the time field.  Basically withers allow each field to be updated 
> independently. That is JEP 468 sort of increases the API of existing 
> code. 
>
> So I wonder if a safer backward compatibility is to provide some sort 
> of marker annotation? e.g. `@Withers` placed on the record or some 
> other way to mark that the record is safe to have withers.
>
> Thoughts?
>
> Cheers
> -Adam