Duplicate property when using discriminatormappings to handle inheritance

[Lavan]

The following definition

openapi: 3.0.0
info:
  version: 1.0.0
  title: Bug
  description: |
    Bug example
  license:
    name: CC0
    url: https://creativecommons.org/publicdomain/zero/1.0/
components:
  schemas:
    Base:
      discriminator:
        propertyName: discriminatorType
        mapping:
          SubClass: "#/components/schemas/SubClass"
      type: object
      required:
        - discriminatorType
      properties:
        discriminatorType:
          type: string
    SubClass:
      allOf:
        - $ref: "#/components/schemas/Base"
      type: object
      required:
        - discriminatorType
        - subClass
        - specific
        - data
      properties:
        discriminatorType:
          type: string
        subClass:
          type: string
        specific:
          type: string
        data:
          type: string
paths:
  /:
    get:
      operationId: dummy
      responses:
        "204":
          description: Nothing

Generates the following interfaces

export interface Base {
  discriminatorType: string;
}

---

import { Base } from '../models/base';

export type SubClass = Base & {
'discriminatorType': 'SubClass';
'discriminatorType': string;
'subClass': string;
'specific': string;
'data': string;
};

As you can see the discriminatorType field has been duplicated. The first one is taken from the Base class' discriminator mapping and the second one is from the fields in the SubClass. The definition is generated from a Java record and an interface. As a Java record requires that all fields must be defined it's not possible to remove it from the subclass.

As a workaround it's possible to "fix" this by setting the discriminator property as hidden but that simply removes the property from the api definition which can cause issues when using it in other places.

After looking at the code a bit I believe the code here should include a check to see if the property is already added.

https://github.com/cyclosproject/ng-openapi-gen/lib/model.ts#L127

[luisfpg]

Is it correct to duplicate discriminatorType in the subclass?