Highlight changed Binder behavior for hidden fields in Vaadin 25 Upgrade guide

[davidvassen]

Describe your motivation

We're currently upgrading from Vaadin 24 to Vaadin 25 and run into a couple of issues due to bindings not being processed properly anymore when fields are not visible.

I understand this was a conscious change that was introduced with isApplied and isAppliedPredicate in the Binding class. However, we personally consider this a rather breaking change and were surprised to not find any mention about this in the upgrade guide.

Describe the solution you'd like

Please add this to the upgrade guide, plus a recommendation how to restore the old behavior. We have so many forms and going through all of them would require a lot of time.

I guess the code below is a possible workaround, but it would be great to have some kind of property on the binder that can be easily set.

getBindings().forEach(binding -> binding.setIsAppliedPredicate(_ -> true));

[mheicke]

To give additional information from my point of view, the problem is: "Values of hidden fields are no longer written to the bean when the binder writes values (e.g., binder.writeBeanIfValid() or binder.writeBean())."

Before Vaadin 25: binder would write the field's value to the bean regardless of the field's visibility.
After Vaadin 25: binder skips hidden fields — so even if you programmatically set a value on a hidden field, it never reaches the bean, causing downstream validation or null errors.

I understand that some people might prefer the version, where it is not written, but if this was intentionally and not a bug, this is a very big breaking change and should have at least been addressed in the change log.

Ideally, there could be a feature flag to opt into the new behavior like:binder.setAcceptHiddenFields(false); with "true" being the default value for downward compatibility.

[knoobie]

Crossref: vaadin/docs#4968

You aren't alone 😬

[mshabarov]

there could be a feature flag to opt into the new behavior like:binder.setAcceptHiddenFields(false); with "true" being the default value for downward compatibility.

Makes sense to add, thanks!
Upgrade guide indeed should mention it. Let's us consider both code change and docs supplement.

[mheicke]

@mshabarov thank you so much - this is the kind of response which makes me happy working with Vaadin :) if you need any additional information (for example why exactly this is a problem for us or how we currently try to implement a hack to solve it for us) feel free to ping me :)