[Java] [3.0.0]Generate same field both in Parent and SubClass when using allOf

Description

Generated model:

public class CommonResponse implements Serializable {

  private static final long serialVersionUID = 1L;
@SerializedName("errcode")
  private Integer errcode = null;
  @SerializedName("errmsg")
  private String errmsg = null;

The subclass should not contain "errcode" and "errmsg". This will cause gson error.

public class AccessToken extends CommonResponse implements Serializable {

  private static final long serialVersionUID = 1L;
@SerializedName("errcode")
  private Integer errcode = null;
  @SerializedName("errmsg")
  private String errmsg = null;
  @SerializedName("access_token")
  private String accessToken = null;
  @SerializedName("expires_in")
  private Integer expiresIn = null;

Swagger-codegen version

61c2b6e4aac269c49b4e5d045d87531e69709be1

Swagger declaration file content or url

openapi: 3.0.1
info:
  title: wechatApi
  license:
    name: Apache 2.0
    url: https://www.apache.org/licenses/LICENSE-2.0.html
  version: 0.0.1
servers:
  - url: https://qyapi.weixin.qq.com/cgi-bin
paths:
  /gettoken:
    get:
      tags:
        - get AccessToken
      summary: access_token
        
      responses:
        '200':
          description: 返回 AccessToken
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/AccessToken'
components:
  schemas:
    CommonResponse:
      type: object
      required:
        - errcode
      properties:
        errcode: 
          type: integer
          format: int32
        errmsg:
          type: string
    AccessToken:
      allOf:
        - $ref: '#/components/schemas/CommonResponse'
        - type: object
          required:
            - access_token
            - expires_in
          properties:
            access_token:
              type: string
            expires_in:
              type: integer
              format: int32

Suggest a fix/enhancement

This line also adds properties from parent to the subModel.

io.swagger.codegen.languages.DefaultCodegenConfig
addProperties(properties, required, composed, allDefinitions);

Start at DefaultCodegenConfig.java around the addProperties(properties, required, composed, allDefinitions) call referenced in the issue. Use the supplied OpenAPI allOf schema to inspect generated CommonResponse and AccessToken models. Done means inherited errcode and errmsg appear only in the parent model and the generated Java output no longer triggers the reported Gson error.