SonarCloud remove candidate rule: java:S1168 Empty arrays and collections should be returned instead of null

[CDellaGiusta]

This poll closes Friday, April 18th 2025.

Candidate rule for removal: java:S1168
Number of issues with this rule in Uyuni: 49
Rule: Empty arrays and collections should be returned instead of null
Software qualities impacted: MAINTAINABILITY
Why is this an issue:

Returning ++null++ instead of an actual array, collection or map forces callers of the method to explicitly test for nullity, making them more complex and less readable.

Moreover, in many cases, ++null++ is used as a synonym for empty.

Should it be removed?:
Legacy code could checking for null with a certain meaning in the caller (where an empty list could mean something else).

All rule issues in Uyuni: https://sonarcloud.io/project/issues?languages=java&issueStatuses=OPEN%2CCONFIRMED&id=uyuni-project_uyuni&rules=java%3AS1168

Examples in our code:

private List<Hunk> step(String[] oldFile, String[] newFile) {
    ....
  return null; //null means we need to step again.
}

protected static Map<String, Object> lookupDataMapByName(CobblerConnection client,String name, String lookupMethod) {
      Object obj = client.invokeMethod(lookupMethod, name);
      if ("~".equals(obj)) {
          return null;
      }
      Map<String, Object> map = (Map<String, Object>) obj;
      if (map == null || map.isEmpty()) {
          return null;
      }
      return map;
  }

[rjmateus]

As you say, this can have a high risk in a code base as old as this one. If somewhere it's checking for null and we change the logic to always return an object we are change the method behaviour, and this kind of issues are normally hard to debug and find.