Steps to Reproduce

Use

<datebox constraint="no empty" valueInLocalDate="@bind(date)"/>

When you bind to value attribute, the constraint will only be validated on save. But for valueInLocalDate it is also validated on load.

Checkout:

https://zkfiddle.org/sample/3vrn709/1-datebox-with-constraint

Current Result

When opening the form and date is null, you'll get a

org.zkoss.zk.ui.WrongValueException: This field may not be empty or contain only spaces.

Expected Result

Not to validate the constraint on loading the data. but on saving.

Debug Information

Workaround