[BUG] Multi Level Inheritance not generated correctly

[rlsf]

As can be seen in these issues:
#1685
#2928

there is a problem with generating multi-level hierarchy with OpenAPI 4.x.x and 5.x.x.
the problem exists in numerous languages that we tested so we guess that it is a problem with the main code.

For example for the yaml below taken from issue 1685 version 3.3.4 generates the expected

class Animal {…}
class Cat extends Animal {…}
class Dog extends Animal {…}
class BigDog extends Dog {…}

While 4.xx and 5.xx generate

class Animal {…}
class Cat extends Animal {…}
class Dog extends Animal {…}
class BigDog {…}

generation was executed using the maven-openapi-generator of the respective version (4.x.x and 5.x.x)

openapi: 3.0.0
info:
  title: Sample API
  description: API description in Markdown.
  version: 1.0.0
paths:
  /animals:
    get:
      summary: Returns all animals.
      description: Optional extended description in Markdown.
      responses:
        200:
          description: OK
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/Animal'
components:
  schemas:
    Dog:
      allOf:
        - $ref: '#/components/schemas/Animal'
        - type: object
          properties:
            breed:
              type: string
    Cat:
      allOf:
        - $ref: '#/components/schemas/Animal'
        - type: object
          properties:
            breed:
              type: string
    BigDog:
      allOf:
        - $ref: '#/components/schemas/Dog'
        - type: object
          discriminator:
            propertyName: dogType
            required:
              - dogType
          properties:
            dogType:
              type: string
            declawed:
              type: boolean
    Animal:
      type: object
      discriminator:
        propertyName: className
      required:
        - className
      properties:
        className:
          type: string
        color:
          type: string
          default: red

[andys8]

Having an issue with Elm and 4.0.0 release and inheritance, too.

[papegaaij]

It seems the check for a discriminator only looks one level up. Repeating the discriminator in the intermediate type (Dog in the example) seems to fix the inheritance.

Update: this unfortunately generates java code that does not compile:

src/main/java/org/openapitools/client/model/Dog.java:[40,9] className has private access in org.openapitools.client.model.Animal

It tries to set the discriminator in the superclass from the constructor of the subclass. Redefining the className property in the subtypes fixes this, but duplicates the discriminiator in every type.

[jimschubert]

Fixed by #4503 please evaluate and let us know if it needs to be reopened.