StringToIntegerConverter makes TextField throw NullPointerException on null Integer value

Vaadin 14.0.9. Binding a null Integer field to a TextField via StringToIntegerConverter fails with NPE. This is the most basic use-case which simply must work out of the box.

[Legioth]

https://github.com/vaadin/flow/pull/6757 adds a mention of null representations to the exception message.

[mvysny]

@Legioth very good point with magic+DI, I avoid DI like a plague.

Maybe we should make Binder catch any exception from setValue and rethrow with a more specific message in the case of passing null to a field with a non-null getEmptyValue()?

That sounds really good. Rethrowing as RuntimeException changes exception type which should be avoided. Rethrowing only in special case as described above sounds good to me, and navigates the dev to the correct solution.

We could also consider whether there would be some alternative way of defining explicit null conversion with less boilerplate, e.g. as an optional parameter to the converter constructor. This would on the other hand have a negative impact on code readability.

Yeah, StringToIntegerConverter already has 4 constructors and with optional boolean param there would be too many. We could add converter.withNullValue("") but there’s no point since we can already call binding.withNullRepresentation(""). I think rethrow is the best solution.