CustomPropertyComparator should be used compare Collection items

[bartoszwalacik]

Currently, CustomPropertyComparator is used only for comparing object properties, for example, it can be used to compare Person objects in boss property:

class Company {
        private Person boss
        private List<Person> partners
}

But it is not used by JaVers to compare Person objects when they are collection items in the partners List.

Possible solution is a new method in CustomPropertyComparator with default impl:

   /**
     * This comparator is called by JaVers to calculate collection-to-collection diff.
     * <br/>
     * For example, when objects of type T are List items.
     * <br/><br/>
     * 
     * Both equals() and compare() should return consistent results. When compare() returns null,
     * equals() should return false.
     * 
     */
    default boolean equals(T a, T b) {
        return Objects.equals(a, b);
    }

[bartoszwalacik]

released in 4.0.0-RC3

[baumgartner]

Works with ListCompareAlgorithm.SIMPLE
Assert fails for ListCompareAlgorithm.AS_SET and LEVENSHTEIN_DISTANCE.
Test-Project available at https://github.com/baumgartner/javerstest/blob/master/src/test/java/javers/test/ListCompareTest.java

[bartoszwalacik]

omg, so we need a fix ...

[bartoszwalacik]

Fixed in 5.0.1 when CustomPropertyComparator is used with LEVENSHTEIN.
CustomPropertyComparator can't be used with AS_SET because for comparing Sets, we need both equals() and hashCode() and CustomPropertyComparator implements only custom equals()

[dmitry-weirdo]

@bartoszwalacik any perspective to also be able to use CustomPropertyComparator together with CustomPropertyComparator?

I described my case on #1038.