[BUG][JAVA] OpenAPI 3.1.0: Wrong generation of Model-Classes when object has multiple object arrays

[HarleyDavidson86]

Description

In my API I have an object with two object arrays. When I generate the java classes the first list has the correct list type,
the second has the type "Object", which is wrong.

openapi-generator version

7.2.0

OpenAPI declaration file content or url

openapi: 3.1.0
info:
  title: Example
  version: 0.0.1
components:
  schemas:
    ParentObject:
      type: object
      properties:
        listOfChildren1:
          type: array
          items:
            $ref: '#/components/schemas/ChildObject'
        listOfChildren2:
          type: array
          items:
            $ref: '#/components/schemas/ChildObject'
        listOfChildren3:
          type: array
          items:
            $ref: '#/components/schemas/ChildObject'
    ChildObject:
      type: object
      properties:
        testProp:
          type: string

Generation Details

Classes are generated with openapi-generator generate -g java -i openapi3_1.yaml -o output

Steps to reproduce

Just generate the classes with the command above.

Suggest a fix

The properties of class "ParentObject" should be a list type, not an object.
This is what's being generated:

public class ParentObject {
  public static final String SERIALIZED_NAME_LIST_OF_CHILDREN1 = "listOfChildren1";
  @SerializedName(SERIALIZED_NAME_LIST_OF_CHILDREN1)
  private List<ChildObject> listOfChildren1;

  public static final String SERIALIZED_NAME_LIST_OF_CHILDREN2 = "listOfChildren2";
  @SerializedName(SERIALIZED_NAME_LIST_OF_CHILDREN2)
  private Object listOfChildren2 = null; //should be of type List<ChildObject>

  public static final String SERIALIZED_NAME_LIST_OF_CHILDREN3 = "listOfChildren3";
  @SerializedName(SERIALIZED_NAME_LIST_OF_CHILDREN3)
  private Object listOfChildren3 = null; //should be of type List<ChildObject>
  (...)

but it should be

public class ParentObject {
  public static final String SERIALIZED_NAME_LIST_OF_CHILDREN1 = "listOfChildren1";
  @SerializedName(SERIALIZED_NAME_LIST_OF_CHILDREN1)
  private List<ChildObject> listOfChildren1;

  public static final String SERIALIZED_NAME_LIST_OF_CHILDREN2 = "listOfChildren2";
  @SerializedName(SERIALIZED_NAME_LIST_OF_CHILDREN2)
  private List<ChildObject> listOfChildren2; //correct type

  public static final String SERIALIZED_NAME_LIST_OF_CHILDREN3 = "listOfChildren3";
  @SerializedName(SERIALIZED_NAME_LIST_OF_CHILDREN3)
  private List<ChildObject> listOfChildren3; //correct type
  (...)

of course with the right setter and getter methods as these from "listOfChildren1".

[jpfinne]

openapi 3.1.0 is currently not fully supported.
If you switch to 3.0.1, then the generated class is correct.

The title of the issue should specify 3.1.0.

Btw if you want to reuse elements, it is better to create a dedicated element like

ListOfChildObject:
 type: array
 items:
      $ref: '#/components/schemas/ChildObject'

[vanrenter]

For the record, I had the same issue with 7.2.0 and it seems fixed by just switching to 7.5.0.
Maybe linked to this PR : #18313