Hi,

We are refining the value extraction work and one of the remaining tasks is to throw a proper exception if we have ValueExtractors defined in parallel hierarchies for a given type.

This led to discovering the below issue with the JavaFX collection types.

Let's take the ListProperty example (we have the same issue with Set and Map): ListProperty inherits from ObservableValue and from List.

For now, it uses (by chance) the ObservableValue extractor which unwraps the value by default. So basically:

@NotNull

private ListProperty<String> listProperty = new ReadOnlyListWrapper<String>( null );

will return a violation.

With the new conflict detection, it will throw an exception as it's unable to find ONE most specific ValueExtractor as there are 2 valid candidates: ObservableValueValueExtractor and ListValueExtractor.

If we want to solve the conflict, we need to introduce a specific ValueExtractor for ListProperty and decide of its behavior.

We have 2 possibilities:

1/ consider ListProperty as an ObservableValue and thus simply unwrap the list and validate the constraint against the list. In the above example, @NotNull would then apply to the inner list. Same behavior as explained above.

2/ consider ListProperty as a List. Thus the value extractor would iterate over the element of the list. In the above case, it won't return a violation. In the below example, the @NotNull would refer to listProperty itself and the constraints on the elements of the list would be validated:
@NotNull
private ListProperty<@Size(min = 3) String> listProperty = new ReadOnlyListWrapper<String>( null );

Gunnar and I are in favor of 2/ but it changes the current behavior as the @NotNull would refer to the container instead of referring to the wrapped value.

We would really like to have some feedback from people using JavaFX.

Thanks!

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Guillaume