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Comparison of Set of Set non-deterministic

See original GitHub issue

I have a data structure which contains a set of set. When comparing with javers I sometimes get a diff, sometimes not. The test data is static so I would expect an identical output.

Steps To Reproduce

When I run this class containing the two identical objects a1 and a2:

import lombok.Builder;
import lombok.Data;
import org.javers.core.Javers;
import org.javers.core.JaversBuilder;

import java.util.Set;

public class MyTest {

    @Data
    @Builder
    public static class A {
        private Set<B> bs;
    }

    @Data
    @Builder
    public static class B {
        private Set<C> cs;
    }

    @Data
    @Builder
    public static class C {
        private String foo;
    }

    public static void main(String[] args) {
        Javers javers = JaversBuilder.javers().build();

        A a1 = A.builder().bs(Set.of(
                        B.builder()
                            .cs(
                                Set.of(
                                    C.builder().foo("a").build(),
                                    C.builder().foo("b").build()
                                        )).build())).build();

        A a2 = A.builder().bs(Set.of(
                B.builder()
                        .cs(
                                Set.of(
                                        C.builder().foo("a").build(),
                                        C.builder().foo("b").build()
                                )).build())).build();


        for (int i = 0; i < 10; i++) {
            var diff = javers.compare(a1, a2);
            if (diff.hasChanges()) {
                System.out.printf("\n===== Diff at round %d ======\n", i);
                System.out.println(diff);
            }
        }
    }
}

… I receive the following output:

20:51:47.647 [main] DEBUG org.javers.core.JaversBuilder - starting up JaVers ...
20:51:47.724 [main] INFO org.javers.core.JaversBuilder - mappingStyle: FIELD
20:51:47.732 [main] INFO org.javers.core.JaversBuilder - loading JodaAddOns ...
20:51:47.786 [main] INFO org.javers.core.JaversBuilder - loading GuavaAddOns ...
20:51:47.841 [main] DEBUG org.javers.TypeMapper - javersType of 'LocalDateTime' mapped explicitly to ValueType
20:51:47.841 [main] DEBUG org.javers.TypeMapper - javersType of 'LocalDate' mapped explicitly to ValueType
20:51:47.842 [main] INFO org.javers.core.JaversBuilder - using fake InMemoryRepository, register actual Repository implementation via JaversBuilder.registerJaversRepository()
20:51:47.870 [main] INFO org.javers.core.JaversBuilder - JaVers instance started in 225 ms
20:51:47.890 [main] DEBUG org.javers.TypeMapper - javersType for 'class MyTest$A' defaulted to ValueObjectType
20:51:47.903 [main] DEBUG org.javers.TypeMapper - javersType for 'java.util.Set<MyTest$B>' spawned as SetType from prototype SetType{ baseType: 'interface java.util.Set' }
20:51:47.905 [main] DEBUG org.javers.TypeMapper - javersType for 'class MyTest$B' defaulted to ValueObjectType
20:51:47.907 [main] DEBUG org.javers.TypeMapper - javersType for 'java.util.Set<MyTest$C>' spawned as SetType from prototype SetType{ baseType: 'interface java.util.Set' }
20:51:47.908 [main] DEBUG org.javers.TypeMapper - javersType for 'class MyTest$C' defaulted to ValueObjectType
20:51:47.909 [main] DEBUG org.javers.core.graph.ObjectGraphBuilder - live graph assembled, object nodes: 4, entities: 0, valueObjects: 3
20:51:47.938 [main] DEBUG org.javers.core.graph.ObjectGraphBuilder - live graph assembled, object nodes: 4, entities: 0, valueObjects: 3
20:51:47.949 [main] DEBUG org.javers.core.graph.ObjectGraphBuilder - live graph assembled, object nodes: 4, entities: 0, valueObjects: 3
20:51:47.951 [main] DEBUG org.javers.core.graph.ObjectGraphBuilder - live graph assembled, object nodes: 4, entities: 0, valueObjects: 3

===== Diff at round 1 ======
Diff:
* changes on MyTest$A/ :
  - 'bs' collection changes :
     . 'MyTest$A/#bs/9f83e3c27e7b610b0a0317a0f008f195' removed
     · 'MyTest$A/#bs/f80bbd079e4ee10592dc0f6f850bacb7' added
  - 'bs/9f83e3c27e7b610b0a0317a0f008f195.cs' collection changes :
     . 'MyTest$A/#bs/{hashPlaceholder}/cs/74a563c16582541b5f7d011fe538602a' removed
     . 'MyTest$A/#bs/{hashPlaceholder}/cs/7f2b9fa7d40fb28ae704fb57f5db54ee' removed
  - 'bs/f80bbd079e4ee10592dc0f6f850bacb7.cs' collection changes :
     · 'MyTest$A/#bs/{hashPlaceholder}/cs/74a563c16582541b5f7d011fe538602a' added
     · 'MyTest$A/#bs/{hashPlaceholder}/cs/7f2b9fa7d40fb28ae704fb57f5db54ee' added

20:51:47.971 [main] DEBUG org.javers.core.graph.ObjectGraphBuilder - live graph assembled, object nodes: 4, entities: 0, valueObjects: 3
20:51:47.972 [main] DEBUG org.javers.core.graph.ObjectGraphBuilder - live graph assembled, object nodes: 4, entities: 0, valueObjects: 3

===== Diff at round 2 ======
Diff:
* changes on MyTest$A/ :
  - 'bs' collection changes :
     . 'MyTest$A/#bs/9f83e3c27e7b610b0a0317a0f008f195' removed
     · 'MyTest$A/#bs/f80bbd079e4ee10592dc0f6f850bacb7' added
  - 'bs/9f83e3c27e7b610b0a0317a0f008f195.cs' collection changes :
     . 'MyTest$A/#bs/{hashPlaceholder}/cs/74a563c16582541b5f7d011fe538602a' removed
     . 'MyTest$A/#bs/{hashPlaceholder}/cs/7f2b9fa7d40fb28ae704fb57f5db54ee' removed
  - 'bs/f80bbd079e4ee10592dc0f6f850bacb7.cs' collection changes :
     · 'MyTest$A/#bs/{hashPlaceholder}/cs/74a563c16582541b5f7d011fe538602a' added
     · 'MyTest$A/#bs/{hashPlaceholder}/cs/7f2b9fa7d40fb28ae704fb57f5db54ee' added

20:51:47.978 [main] DEBUG org.javers.core.graph.ObjectGraphBuilder - live graph assembled, object nodes: 4, entities: 0, valueObjects: 3
20:51:47.980 [main] DEBUG org.javers.core.graph.ObjectGraphBuilder - live graph assembled, object nodes: 4, entities: 0, valueObjects: 3
20:51:47.982 [main] DEBUG org.javers.core.graph.ObjectGraphBuilder - live graph assembled, object nodes: 4, entities: 0, valueObjects: 3
20:51:47.983 [main] DEBUG org.javers.core.graph.ObjectGraphBuilder - live graph assembled, object nodes: 4, entities: 0, valueObjects: 3
20:51:47.985 [main] DEBUG org.javers.core.graph.ObjectGraphBuilder - live graph assembled, object nodes: 4, entities: 0, valueObjects: 3
20:51:47.987 [main] DEBUG org.javers.core.graph.ObjectGraphBuilder - live graph assembled, object nodes: 4, entities: 0, valueObjects: 3
20:51:47.989 [main] DEBUG org.javers.core.graph.ObjectGraphBuilder - live graph assembled, object nodes: 4, entities: 0, valueObjects: 3
20:51:47.991 [main] DEBUG org.javers.core.graph.ObjectGraphBuilder - live graph assembled, object nodes: 4, entities: 0, valueObjects: 3

===== Diff at round 6 ======
Diff:
* changes on MyTest$A/ :
  - 'bs' collection changes :
     . 'MyTest$A/#bs/9f83e3c27e7b610b0a0317a0f008f195' removed
     · 'MyTest$A/#bs/f80bbd079e4ee10592dc0f6f850bacb7' added
  - 'bs/9f83e3c27e7b610b0a0317a0f008f195.cs' collection changes :
     . 'MyTest$A/#bs/{hashPlaceholder}/cs/74a563c16582541b5f7d011fe538602a' removed
     . 'MyTest$A/#bs/{hashPlaceholder}/cs/7f2b9fa7d40fb28ae704fb57f5db54ee' removed
  - 'bs/f80bbd079e4ee10592dc0f6f850bacb7.cs' collection changes :
     · 'MyTest$A/#bs/{hashPlaceholder}/cs/74a563c16582541b5f7d011fe538602a' added
     · 'MyTest$A/#bs/{hashPlaceholder}/cs/7f2b9fa7d40fb28ae704fb57f5db54ee' added

20:51:47.994 [main] DEBUG org.javers.core.graph.ObjectGraphBuilder - live graph assembled, object nodes: 4, entities: 0, valueObjects: 3
20:51:47.996 [main] DEBUG org.javers.core.graph.ObjectGraphBuilder - live graph assembled, object nodes: 4, entities: 0, valueObjects: 3
20:51:47.997 [main] DEBUG org.javers.core.graph.ObjectGraphBuilder - live graph assembled, object nodes: 4, entities: 0, valueObjects: 3
20:51:47.998 [main] DEBUG org.javers.core.graph.ObjectGraphBuilder - live graph assembled, object nodes: 4, entities: 0, valueObjects: 3
20:51:48.000 [main] DEBUG org.javers.core.graph.ObjectGraphBuilder - live graph assembled, object nodes: 4, entities: 0, valueObjects: 3
20:51:48.001 [main] DEBUG org.javers.core.graph.ObjectGraphBuilder - live graph assembled, object nodes: 4, entities: 0, valueObjects: 3

===== Diff at round 9 ======
Diff:
* changes on MyTest$A/ :
  - 'bs' collection changes :
     . 'MyTest$A/#bs/9f83e3c27e7b610b0a0317a0f008f195' removed
     · 'MyTest$A/#bs/f80bbd079e4ee10592dc0f6f850bacb7' added
  - 'bs/9f83e3c27e7b610b0a0317a0f008f195.cs' collection changes :
     . 'MyTest$A/#bs/{hashPlaceholder}/cs/74a563c16582541b5f7d011fe538602a' removed
     . 'MyTest$A/#bs/{hashPlaceholder}/cs/7f2b9fa7d40fb28ae704fb57f5db54ee' removed
  - 'bs/f80bbd079e4ee10592dc0f6f850bacb7.cs' collection changes :
     · 'MyTest$A/#bs/{hashPlaceholder}/cs/74a563c16582541b5f7d011fe538602a' added
     · 'MyTest$A/#bs/{hashPlaceholder}/cs/7f2b9fa7d40fb28ae704fb57f5db54ee' added


Process finished with exit code 0

Interestingly enough the diff appears (at least on my machine) always on the same rounds. When the inner set (Set of C) only contains one entry, the diff works as expected - there is no difference 😉

What do I miss?

Javers’ Version 6.42

Additional context