[BUG][JAVA] Generated object has no properties of intermediate parents

[abelan]

Bug Report Checklist

• Have you provided a full/minimal spec to reproduce the issue?
• Have you validated the input using an OpenAPI validator (example)?
• Have you tested with the latest master to confirm the issue still exists?
• Have you searched for related issues/PRs?
• What's the actual output vs expected output?
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Description

Version 4.3.1 generates inherited classes. So D extends C extends B extends A.
But there is no more inheritance as I understood.
So I expect that

• D has properties of C, B, A (first, second, third, fourth)
• C - B and A (first, second, third)

But they get properties of the root class A only

• D: first, fourth
• C: first, third

I'm able to fix it with to following markup

C:
  allOf:
    - $ref: '#/components/schemas/B'
    - type: object
      properties:
        third:
          type: string

but extra C[B]AllOf.java classes are generated.

openapi-generator version

5.1.1

OpenAPI declaration file content or url

openapi: 3.0.2
info:
  title: Example
  version: 0.0.1
servers:
  - url: https://myserver
paths:
  /go:
    post:
      tags:
        - GO
      operationId: go
      requestBody:
        content:
          application/json:
            schema:
              type: object
              properties:
                shortObject:
                  $ref: '#/components/schemas/B'
                longObject:
                  $ref: '#/components/schemas/D'
      responses:
        200:
          description: OK
components:
  schemas:
    A:
      type: object
      properties:
        first:
          type: string
    B:
      allOf:
        - $ref: '#/components/schemas/A'
      type: object
      properties:
        second:
          type: string
    C:
      allOf:
        - $ref: '#/components/schemas/B'
      type: object
      properties:
        third:
          type: string
    D:
      allOf:
        - $ref: '#/components/schemas/C'
      type: object
      properties:
        fourth:
          type: string

Generation Details

Gradle Plugin
generatorName = 'spring'

Steps to reproduce

Run the gradle task with the given yaml