RFR: 8290310: ChangeListener events are incorrect or misleading when a nested change occurs [v12]

[John Hendrikx]

On Mon, 10 Mar 2025 09:27:29 GMT, Michael Strauß <mstrauss at openjdk.org> wrote:

>> John Hendrikx has updated the pull request incrementally with three additional commits since the last revision:
>> 
>>  - Small fixes from review comments
>>  - Use switch expression where reasonable
>>  - Update docs regarding NullPointerExceptions
>
> modules/javafx.base/src/main/java/com/sun/javafx/binding/ListenerList.java line 174:
> 
>> 172:                  */
>> 173: 
>> 174:                 throw new StackOverflowError("non-converging value detected in value modifying listeners on " + observableValue + "; original value was: " + oldValue);
> 
> We shouldn't throw errors, even if that's what the old implementation would implicitly do (not that it matters, no sane application would ever try to catch a `StackOverflowError` as part of its normal control flow). I think a `RuntimeException` is in order.
> 
> Also maybe make the message a bit clearer:
> `<observableValue> was changed during the invocation of multiple listeners, but the new values diverge [original value: <oldValue>]`

Maybe it should only be a warning log. Any exception a listener may throw is currently only logged so other listeners may still continue to work correctly.  Throwing an `Error` was a nice way around that, but does potentially leave some listeners uninformed of a change or invalidation (same as `ExpressionHelper` in that regard).

If we go for a runtime exception, I'd need to allow the exception to pass through, but the same thing still applies that breaking it off with an exception may leave some listeners uninformed.  So I think we need to decide, how "bad" is this problem, and does it warrant terminating the application.

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PR Review Comment: https://git.openjdk.org/jfx/pull/1081#discussion_r1987032716