Stopping diff to go one level deep

[tarunlalwani]

I have a normal program which does below

package com.javerstest;

import com.google.common.collect.ImmutableList;
import org.javers.core.Javers;
import org.javers.core.JaversBuilder;
import org.javers.core.diff.Diff;
import org.javers.core.diff.ListCompareAlgorithm;

import java.util.List;

public class App {


    public static void main(String[] args) {

        List<ListItem> list1 = ImmutableList.of(
                ListItem.builder()
                        .itemName("item1")
                        .itemValue("value")
                        .build(),
                ListItem.builder()
                        .itemName("item2")
                        .itemValue("value2")
                        .build()
        );

        List<ListItem> list2 = ImmutableList.of(
                ListItem.builder()
                        .itemName("item2")
                        .itemValue("value2change")
                        .build(),
                ListItem.builder()
                        .itemName("item1")
                        .itemValue("value")
                        .build(),
                ListItem.builder()
                        .itemName("item3")
                        .itemValue("value3")
                        .build()

        );

        TopLevelClass tlc1 = TopLevelClass.builder().items(list1).build();
        TopLevelClass tlc2 = TopLevelClass.builder().items(list2).build();

        Javers jvc = JaversBuilder.javers().withListCompareAlgorithm(ListCompareAlgorithm.AS_SET)
                .build();
        Diff diffTlc = jvc.compare(tlc1, tlc2);
        System.out.println(diffTlc);
    }
}

package com.javerstest;

import lombok.Builder;
import lombok.EqualsAndHashCode;
import lombok.Getter;
import lombok.Setter;

@Builder
@Getter
@Setter
@EqualsAndHashCode
public class ListItem {
    private String itemName;
    private String itemValue;
}

package com.javerstest;

import lombok.Builder;
import lombok.EqualsAndHashCode;
import lombok.Getter;
import lombok.Setter;
import org.javers.core.metamodel.annotation.IgnoreDeclaredProperties;
import org.javers.core.metamodel.annotation.ShallowReference;

import java.util.List;
import java.util.Set;


@Builder
@Getter
@Setter
@EqualsAndHashCode
public class TopLevelClass {

    @ShallowReference
    List<ListItem> items;
}

Below is the repo if you need to have a look

https://github.com/tarunlalwani/javers-diff-issue

Now when you run the diff is like below

* new object: com.javerstest.TopLevelClass/#items/2
* changes on com.javerstest.TopLevelClass/ :
  - 'items' collection changes :
    . 'com.javerstest.ListItem@306a04bf' removed
    . 'com.javerstest.ListItem@306a04fb' added
    . 'com.javerstest.ListItem@29f62baf' added
  - 'items/0.itemName' changed from 'item1' to 'item2'
  - 'items/0.itemValue' changed from 'value' to 'value2change'
  - 'items/1.itemName' changed from 'item2' to 'item1'
  - 'items/1.itemValue' changed from 'value2' to 'value'

All the changes are actually covered by below

  - 'items' collection changes :
    . 'com.javerstest.ListItem@306a04bf' removed
    . 'com.javerstest.ListItem@306a04fb' added
    . 'com.javerstest.ListItem@29f62baf' added

But javers still goes one level deep again in the list and does another comparison and adds below

  - 'items/0.itemName' changed from 'item1' to 'item2'
  - 'items/0.itemValue' changed from 'value' to 'value2change'
  - 'items/1.itemName' changed from 'item2' to 'item1'
  - 'items/1.itemValue' changed from 'value2' to 'value'

Bug/feature/limitation? Need to understand. If the list has been already compared, I don't want it to go one level deep again and of course @ShallowReference doesn't help

[bartoszwalacik]

That's how Javers works. You can use @ShallowReference to limit the diff scope or other annotations described here
https://javers.org/documentation/domain-configuration/#ignoring-things

[tarunlalwani]

@bartoszwalacik , thanks! Really appreciate the response

[bartoszwalacik]

Okay, looks like that you can't compare Value Objects in List wit AS_SET algorithm.

Normally, when a Value Object is in Set, its Id is generated using ObjectHasher, for example:

org.javers.core.cases.CaseListOfValueObjects$TopLevelClass/#items/4515e04193acc0f8bff590e9c0fd5837

If Value Object is in List, its Id is based on its index in this List, for example:

org.javers.core.cases.CaseListOfValueObjects$TopLevelClass/#items/0

When you AS_SET is chosen, Id should be generated using ObjectHasher for both Set and List containers

[tarunlalwani]

So pottenitaly a bug that you would fix?

[bartoszwalacik]

yes

[bartoszwalacik]

fixed in release 3.9.5