[BUG][php-nextgen] Discriminator values used for allowed enum values

[coffeemakr]

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• Have you provided a full/minimal spec to reproduce the issue?
• Have you validated the input using an OpenAPI validator?
• 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

If I have a schema, that has a oneOf discriminator and a type:

components:
  schemas:
    Pet:
      type: object
      properties:
        id:
          type: string
          minLength: 1
        animal:
          oneOf:
            - $ref: '#/components/schemas/Dog'
            - $ref: '#/components/schemas/Cat'
          discriminator:
            propertyName: type
            mapping:
              pet-dog: '#/components/schemas/Dog'
              pet-cat: '#/components/schemas/Cat'
    Dog:
      type: object
      properties:
        type:
          type: string
          enum: ["pet-dog"]
          default: "pet-dog"
        imageId:
          type: string
      required:
        - type
        - imageId
    Cat:
      type: object
      properties:
        type:
          type: string
          enum: ["pet-cat"]
          default: "pet-cat"
        imageId:
          type: string
        style:
          type: string
          enum:
            - "page"
            - "text"
            - "viewport"
      required:
        - type
        - imageId
        - style

The generated cobined class has a incorrect style allowed values in PetAnimal.php:

The following code is generated in

    public const TYPE_PET_CAT = 'pet-cat';
    public const TYPE_PET_DOG = 'pet-dog';

    /**
     * Gets allowable values of the enum
     *
     * @return string[]
     */
    public static function getTypeAllowableValues()
    {
        return [
            self::TYPE_PET_CAT,
            self::TYPE_PET_DOG,
        ];
    }

    /**
     * Gets allowable values of the enum
     *
     * @return string[]
     */
    public static function getStyleAllowableValues()
    {
        return [
            self::TYPE_PET_CAT,
            self::TYPE_PET_DOG,
        ];
    }

openapi-generator version

OpenAPI declaration file content or url

Generation Details

Steps to reproduce

I make a test: https://github.com/coffeemakr/openapi-generator/tree/issues-23813

Related issues/PRs

Suggest a fix