Summary

Describe allowable types of evolution compatible changes to serializable record classes.

Problem

The record-specific Java Object Serialization specification is silent on the types of changes that can be made to record classes while maintaining compatibility with preview serial versions.

Solution

In subsection 5.6.2 - "Compatible Changes", add allowable types of evolution compatible changes that can be made to serializable record classes.

Specification

5.6.2 Compatible Changes

...
-   Adding or removing a record component - When the record object being
    reconstituted has a record component that does not occur in the stream, the
    record class's canonical constructor will be passed the default value for
    its type. If specific initialization is needed, the constructor can
    initialize the component to a non-default value. Stream field values not
    passed to the canonical constructor are effectively discarded.

-   Changing a class from an ordinary class to a record class - A class that is
    suitable to be converted from an ordinary class to a record class, and
    relies on default serialization, may be changed to a record class. The
    ordinary class should have `java.lang.Object` as its direct superclass, or
    otherwise have no serializable state in its superclasses. The name and type
    of the record class's components must match that of the name and type of the
    ordinary class's serializable fields. Record objects are reconstructed
    through the record class's canonical constructor. If the canonical
    constructor throws an exception, say while checking invariants, then an
    `InvalidObjectException` is thrown.

-   Changing a class from a record class to an ordinary class - A record class
    that relies on default serialization, may be changed to an ordinary class.
    The ordinary class must declare an explicit `serialVersionUID`, whose value
    is the same as that of the prior record class's `serialVersionUID`, or
    `0L` if the prior record class does not have an explicit `serialVersionUID`
    declaration. The name and type of the ordinary class's serializable fields
    must match that of the name and type of the prior record class's components.

Viewable online at: https://cr.openjdk.java.net/~chegar/records/spec/records-serialization-addendum.html