DateRangePicker.clear() throws NPE

[Dudeplayz]

The default implementation of clear in HasValue uses the default getEmptyValue, which is null. I am not sure what should happen if clear is called, but a NPE should never occur. I think it should jump back to the defaultModel.

java.lang.NullPointerException: null
	at software.xdev.vaadin.daterange_picker.ui.DateRangePicker.tryFixInvalidModel(DateRangePicker.java:355) ~[vaadin-date-range-picker-2.0.0.jar:2.0.0]
	at software.xdev.vaadin.daterange_picker.ui.DateRangePicker.updateFromModel(DateRangePicker.java:333) ~[vaadin-date-range-picker-2.0.0.jar:2.0.0]
	at software.xdev.vaadin.daterange_picker.ui.DateRangePicker.setValue(DateRangePicker.java:501) ~[vaadin-date-range-picker-2.0.0.jar:2.0.0]
	at software.xdev.vaadin.daterange_picker.ui.DateRangePicker.setValue(DateRangePicker.java:63) ~[vaadin-date-range-picker-2.0.0.jar:2.0.0]
	at com.vaadin.flow.component.HasValue.clear(HasValue.java:179) ~[flow-server-2.4.2.jar:2.4.2]

[AB-xdev]

This should be fixed with a2854ff

When calling clear() an UnsupportedOperationException is thrown.

[Dudeplayz]

Why not using the default model for clear?

[AB-xdev]

2 reasons:

1. Technical:
   There are constructors that use the defaultModel (maybe we should better rename it to initialModel) directly - without a supplier.
   Due to this the defaultModel is used directly by the component (changes are written immediately to it), which means, that even when you call clear() nothing will happen, because the object would be the same.
2. Logically:
   The clear() method shouldn't even be available, because when you clear a date (or date-range) what is its default value?
   It could be null - which is not a date -
   or a fixed LocalDate (e.g. LocalDate.MIN) - which doesn't "clears" a field.
   So there's a bit of a dilemma here 😐

[Dudeplayz]

That's true. I understand the problem now. I would suggest two additional ideas:

1. Allowing to pass a default value to the constructor, which is set, when clear is called. This would cause the problem, which default value should be used if none is supplied.
2. Store the relevant state information from the initialModel and recover/set these on clear.