ConfigOverride using Nulls.AS_EMPTY does not work with JsonManagedReference

[robrat]

Search before asking

• [X] I searched in the issues and found nothing similar.

Describe the bug

configOverride for Lists work as expected, but if any of the lists is a ManagedReference, then the list is initialized with null instead of an empty list.

Version Information

2.17.1

Reproduction

Without JsonManagedReference and JsonBackReference the children list is initialized with a non null value, but with these annotations it becomes null, but only after I add Value.forContentNulls, otherwise it would throw an IllegalStateException.

class JacksonManagedRefTest {

  @lombok.Getter @lombok.Setter
  static class Parent {
    private String name;

    @JsonManagedReference
    private List<Item> children = new ArrayList<>();
  }

  @lombok.Getter @lombok.Setter
  static class Item {
    private String name;

    @JsonBackReference
    private Parent parent;
  }

  @Test
  void test_nonEmptyChildren() throws Exception {
    ObjectMapper om = new ObjectMapper();

    String str = "{ \"name\": \"parent\", \"children\":[{\"name\":\"child1\"},{\"name\":\"child1\"}]}";
    Parent obj = om.readValue(str, Parent.class);
    Assertions.assertNotNull(obj.children);
  }

  // java.lang.IllegalStateException: Should never try to reset delegate
  @Test
  void test_nullChildren() throws Exception {
    ObjectMapper om = new ObjectMapper();
    om.configOverride(List.class).setSetterInfo(JsonSetter.Value.forValueNulls(Nulls.AS_EMPTY));

    String str = "{ \"name\": \"parent\", \"children\": null }";
    Parent obj = om.readValue(str, Parent.class);
    Assertions.assertNotNull(obj.children);
  }

  // not null assertion fails
  @Test
  void test_nullChildren_contentNullConfig() throws Exception {
    ObjectMapper om = new ObjectMapper();
    om.configOverride(List.class).setSetterInfo(JsonSetter.Value.forValueNulls(Nulls.AS_EMPTY));
    om.configOverride(List.class).setSetterInfo(JsonSetter.Value.forContentNulls(Nulls.AS_EMPTY));

    String str = "{ \"name\": \"parent\", \"children\": null }";
    Parent obj = om.readValue(str, Parent.class);
    Assertions.assertNotNull(obj.children);
  }
}

Expected behavior

List property children is initialized with an empty list

Additional context

No response

[cowtowncoder]

Quick note: first of all; thank you for reporting the issue and providing a test case.

Unfortunately we would need a reproduction that does not use Lombok, since project cannot add a Lombok dependency (even for tests).

Removing Lombok use could use verify that this problem is not due to Lombok processing (which is possible if not probably root cause).

[cowtowncoder]

Also: while I don't think there is difference, trying with 2.18.0 would be good, to ensure issue has not been resolved in the latest minor version upgrade.

[robrat]

I mostly used lombok to get a shorter unit test without the getter/setter noise. I removed lombok and also tried jackson 2.18, but without success. I pushed the change as a separate repo: https://github.com/robrat/jackson-nullasempty