review fix: Filter extends Predicate is now working with projects in JDK7

[surli]

This PR intends to fix the bug introduced in #1798 which make projects using JDK7 and custom filters fail. The error comes from the usage of a default method: overriding it in AbstractFilter fixes the bug.

[pvojtechovsky]

I wonder how these projects works? Are they compiling java 8 library (spoon) using java 7 compatible compiler?

Anyway if it helps, I am OK to merge it. This PR is OK for me.

[monperrus]

really good, thanks!

[surli]

Ok actually this was not a proper fix: code that implements the interface Filter might be broken too.
So, either I completely remove the extends Predicate on AbstractFilter, or we consider the change as breaking for JDK7.

Are they compiling java 8 library (spoon) using java 7 compatible compiler?

They are using a JDK 8 but the pom.xml target a Java 7 binary, so I assume the default method are not managed in the produced binary leading to a compilation error.

[pvojtechovsky]

lets remove Predicate from Filter. It is not so great idea - if it breaks compatibility. We can add it again later after some years ... after everybody migrates

[surli]

We can add it again later after some years ... after everybody migrates

Actually I thought that AbstractFilter was more used, so we would be able to implement it in there, but no: AbstractFilter is almost a specific kind of Filter, not really an abstract filter.

I think a good first step, might be to refactor the hierarchy of filters to create a real abstract filter class that - in the future - we can enrich if needed.

[pvojtechovsky]

to refactor the hierarchy of filters to create a real abstract filter class

I think on many places in spoon there is already used Filter implementation using Lambda

anElement.filterChildren((CtAnnotation m) -> val.equals(m.getValue(...)))...

There is no way how to replace it by AbstractFilter, without making code ugly again.

[surli]

There is no way how to replace it by AbstractFilter, without making code ugly again.

Hmmm indeed.