[BUG][Spring] Inheritance being generated incorrectly - v6.3.0

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• 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?
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• What's the actual output vs expected output?
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Description

Hello, could someone explain to me the correct way to achieve an inheritance relationship with two classes? In my example I have the following schemas:

openapi: 3.0.3
#...
paths:
  /categories:
    get:
      summary: List categories
      description: Lists categories taking into account pagination information, if provided.
      operationId: listCategories
      tags:
        - Categories
      parameters:
        - $ref: "#/components/parameters/orderBy"
        - $ref: "#/components/parameters/limit"
        - $ref: "#/components/parameters/page"
      responses:
        200:
          description: OK
          content:
            application/json:
              schema:
                $ref: "#/components/schemas/CategoryDtoPagination"
        422:
          $ref: "#/components/responses/UnprocessableEntity"

  /transactions:
    get:
      summary: List transactions.
      description: Lists transactions taking into account paging information, if provided.
      operationId: listTransactions
      tags:
        - Transactions
      parameters:
        - $ref: "#/components/parameters/orderBy"
        - $ref: "#/components/parameters/limit"
        - $ref: "#/components/parameters/page"
      responses:
        200:
          description: OK
          content:
            application/json:
              schema:
                $ref: "#/components/schemas/TransactionDtoPagination"
        422:
          $ref: "#/components/responses/UnprocessableEntity"

components:
  schemas:
    CategoryDtoPagination:
      description: Uses the PaginationData base object.
      allOf:
        - $ref: "#/components/schemas/PaginationData"
      properties:
        elements:
          type: array
          items:
            $ref: "#/components/schemas/CategoryDto"

    TransactionDtoPagination:
      description: Uses the PaginationData base object.
      allOf:
        - $ref: "#/components/schemas/PaginationData"
      properties:
        elements:
          type: array
          items:
            $ref: "#/components/schemas/TransactionDto"

    PaginationData:
      type: object
      properties:
        pageNumber:
          type: integer
          format: int32
          description: Current page number.
        pageSize:
          type: integer
          format: int32
          description: Represents the maximum size of the page being returned.
        totalPages:
          type: integer
          format: int32
          description: Total pages
        totalElements:
          type: integer
          format: int64
          description: Total elements
      discriminator:
        propertyName: PaginationData
#...

As I don't have a type or id property in the schema PaginationData I put the name of the schema itself for this test. With the discriminator property added to the schema, classes are generated perfectly with extends, as in the example below:

public class CategoryDtoPagination extends PaginationData {
//...
}

When I remove the discriminator property from the PaginationData schema, all other schemas that are defined with allOf and that should inherit from PaginationData do not have the extends. Ex:

public class CategoryDtoPagination {
//...
}

I've already analyzed some open issues, but I still couldn't understand clearly how the inheritance process should be generated. Excuse my ignorance, but I don't see the need to include a type or id property in the PaginationData schema so that the other classes inherit from PaginationData. Does anyone have a different view? Or if this would be a bug?

openapi-generator version

v6.3.0

Steps to reproduce

Carry out the generation process with one or more schemas using the allOf property referencing another schema.

Start by running the Spring generator with the supplied OpenAPI YAML on version 6.3.0, comparing output with and without the PaginationData discriminator. Trace the generator's allOf and discriminator handling for CategoryDtoPagination and TransactionDtoPagination. Done means the intended inheritance behavior is established and the generated Java classes consistently reflect it, with regression coverage if the behavior is confirmed as a bug.