[BUG] Code is not generated correctly for allOf.

Created by: jeff9finger

Description

I am not able to get the following definition to generate java or type script correctly.

Have tried with 4.3.1. In Java, RealCommand is generated as

public class RealCommand extends Command {
...
}

Notice that I did not specify a discriminator in Command. I expect this definition to generate a composition of Command and RealCommand.java and that Command.java would not be generated. Command.java file is not generated, but it is also expected as a base class in RealCommand.java, so this does not compile.

There should not be any inheritance here because there is no discriminator.

openapi-generator version

4.3.1

Bug Report Checklist

• Have you provided a full/minimal spec to reproduce the issue?
• Have you validated the input using an OpenAPI validator (example)?
• What's the version of OpenAPI Generator used? - 4.3.1
• Have you search for related issues/PRs? - yes
• What's the actual output vs expected output?
• [Optional] Bounty to sponsor the fix (example)

OpenAPI declaration file content or url

swagger: "2.0"
info:
  title: Test Command model generation
  description: Test Command model generation
  version: 1.0.0
host: localhost:8080
schemes:
  - https
definitions:
  Command:
    title: Command
    description: The base object for all command objects.
    x-swagger-router-model: CommandDto
    type: object
    properties: {}
  RealCommand:
    title: RealCommand
    description: The real command.
    x-swagger-router-model: RealCommandDto
    allOf:
      - $ref: '#/definitions/Command'
  ApiError:
    description: The base object for API errors.
    x-swagger-router-model: ApiGeneralException
    type: object
    required:
    - code
    - message
    properties:
      code:
        description: The error code. Usually, it is the HTTP error code.
        type: string
        readOnly: true
      message:
        description: The error message.
        type: string
        readOnly: true
    title: ApiError

parameters:
  b_real_command:
    name: real_command
    in: body
    description: A payload for executing a real command.
    required: true
    schema:
      $ref: '#/definitions/RealCommand'

paths:
  /execute:
    post:
      produces: []
      x-swagger-router-controller: FakeController
      operationId: executeRealCommand
      parameters:
      - name: real_command
        in: body
        description: A payload for executing a real command.
        required: true
        schema:
          $ref: '#/definitions/RealCommand'
      responses:
        '204':
          description: Successful request. No content returned.
        '400':
          description: Bad request.
          schema:
            $ref: '#/definitions/ApiError'
        '404':
          description: Not found.
          schema:
            $ref: '#/definitions/ApiError'
        default:
          description: Unknown error.
          schema:
            $ref: '#/definitions/ApiError'

Command line used for generation

openapi-generator generate -i test.yaml -g java --library jersey2 -o java --additional-properties legacyDiscriminatorBehavior=false

Steps to reproduce

Related issues/PRs

https://github.com/OpenAPITools/openapi-generator/issues/2845

Suggest a fix

I see that maybe ModelUtils#isFreeFormObject() should also check to see if the object is used in an allOf, anyOf, or oneOf in any other schema in the definition. But this still does not explain why RealCommand is using Command as a base class.