gen: discriminator property is removed from structures about ogen

[vkuptcov]

@johanhenriksson did you find a workaround for this issue?
The only thing I've found it to define a kind of type alias to use in oneOf schema, e.g.

StringForDiscriminator:
  allOf:
    - $ref: '#/components/types/String'
    - type: object
      properties:
         kind:
           type: string

In that case we have 2 objects generated, one to be used in the case with discriminator, and another one without. But it looks a bit ugly, tbh.
Another solution is to just define a map and put data there

      additionalProperties:
        type: string

[ernado]

So having following schema

openapi: 3.0.3
info:
  title: Discriminator example
  description: Example
  version: 1.0.0
paths:
    /example:
      get:
        responses:
          200:
            description: OK
            content:
              "application/json":
                schema:
                    $ref: '#/components/schemas/Response'
components:
  schemas:
    Alpha:
      type: object
      required:
        - kind
        - variant
        - data
      properties:
        kind:
          type: string
        variant:
          type: string
        data:
          type: string
    Beta:
      type: object
      required:
        - kind
        - variant
        - value
      properties:
        kind:
          type: string
        variant:
          type: string
        value:
          type: string
    SumAuto:
      oneOf:
        - $ref: '#/components/schemas/Alpha'
        - $ref: '#/components/schemas/Beta'
    SumFirst:
      discriminator:
        propertyName: kind
        mapping:
          alpha: '#/components/schemas/Alpha'
          beta: '#/components/schemas/Beta'
      oneOf:
        - $ref: '#/components/schemas/Alpha'
        - $ref: '#/components/schemas/Beta'
    SumSecond:
      discriminator:
        propertyName: variant
        mapping:
          a: '#/components/schemas/Alpha'
          b: '#/components/schemas/Beta'
      oneOf:
        - $ref: '#/components/schemas/Alpha'
        - $ref: '#/components/schemas/Beta'
    Response:
      type: object
      required:
        - Auto
        - First
        - Second
        - Alpha
        - Beta
      properties:
        Auto:
          $ref: '#/components/schemas/SumAuto'
        First:
          $ref: '#/components/schemas/SumFirst'
        Second:
          $ref: '#/components/schemas/SumSecond'
        Alpha:
          $ref: '#/components/schemas/Alpha'
        Beta:
          $ref: '#/components/schemas/Beta'

Discriminator properties are removed from Alpha and Beta, but should not.

@tdakkota please take a look.

[johanhenriksson]

@vkuptcov I have not found a good workaround to this, no. We managed to do without it, but having the discriminator field on the generated types would make life easier.