Openapi-generator: [BUG][C++][QT5] OneOf, AnyOf and AllOf Handling Erroneous

[wunt]

Bug Report Checklist

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

Description

The generated code when using OneOf, AnyOf or AllOf contain errors, i.e.:

1. AllOf: When a schema A for example uses AllOf together with > 1 subschemes (B, C, ...), only the first defined scheme (B) within AllOf is used within the generated client code for the scheme A.
2. AnyOf and OneOf: Some included files are not generated.

openapi-generator version

4.3.1

OpenAPI declaration file content or url

openapi: 3.0.0
info:
  version: 0.0.1
  title: Test
paths:
  /endpointAllOf:
    put:
      operationId: allOf
      description: "-"
      requestBody:
        description: Content All Of
        content:
          application/json:
            schema:
                $ref: '#/components/schemas/SchemaAllOf'
      responses:
        200:
          description: Success
  /endpointOneOf:
    put:
      operationId: oneOf
      description: "-"
      requestBody:
        description: Content One Of
        content:
          application/json:
            schema:
                $ref: '#/components/schemas/SchemaOneOf'
      responses:
        200:
          description: Success
  /endpointAnyOf:
    put:
      operationId: anyOf
      description: "-"
      requestBody:
        description: Content Any Of
        content:
          application/json:
            schema:
                $ref: '#/components/schemas/SchemaAnyOf'
      responses:
        200:
          description: Success

components:
  schemas:
    SchemaAllOf:
      type: object
      description: 'All Of Example'
      properties:
        information:
          type: string
          description: 'Some information field'
        additionalInfo:
          allOf:
          - $ref: '#/components/schemas/OptionA'
          - $ref: '#/components/schemas/OptionB'

    SchemaAnyOf:
      type: object
      description: 'Any Of Example'
      properties:
        information:
          type: string
          description: 'Some information field'
        additionalInfo:
          anyOf:
          - $ref: '#/components/schemas/OptionA'
          - $ref: '#/components/schemas/OptionB'

    SchemaOneOf:
      type: object
      description: 'One Of Example'
      properties:
        information:
          type: string
          description: 'Some information field'
        additionalInfo:
          oneOf:
          - $ref: '#/components/schemas/OptionA'
          - $ref: '#/components/schemas/OptionB'

    OptionA:
      type: object
      description: 'Option A'
      properties:
        data1:
          type: string
          description: 'Data'
    OptionB:
      type: object
      description: 'Option B'
      properties:
        data2:
          type: number
          description: 'Data'

Command line used for generation

java -cp openapi-generator-cli-4.3.1.jar org.openapitools.codegen.OpenAPIGenerator generate -i ${SPEC_FILE} -g cpp-qt5-client -o gen/ --model-name-prefix Test

Steps to reproduce

Execute code generation and take a look at the files (SchemaOneOf.h, SchemaAllOf.h, SchemaAnyOf.h, etc.).

Related issues/PRs

E.g. for oneOf: https://github.com/OpenAPITools/openapi-generator/issues/15

##### Suggest a fix
-

[etherealjoy]

@muttleyxd @stkrwork @ravinikam @MartinDelille
There seems to be a problem to handle in C++

std::variant/std::any

• cannot handle c++ containers
• in case of AnyOf/AllOf members of multiple classes are needed

OneOf

• Exactly one class/type

AnyOf

• Multiple classes/types

AllOf

• All of the classes/types

Easiest way would be to generate separate members for the OneOf/AllOf/AnyOf refs
Then set the class to be valid for the ones for which data arrived.

Do you have some ideas and better proposals?

[wing328]

I think it's an issue with the inline model resolver. As a workaround, please define the schemas (oneOf, anyOf, allOf) separately instead, e.g.

    SchemaAllOf:
      type: object
      description: 'All Of Example'
      properties:
        information:
          type: string
          description: 'Some information field'
        additionalInfo:
          $ref: '#/components/schemas/AllOfOptionAB'
    AllOfOptionAB:
      allOf:
      - $ref: '#/components/schemas/OptionA'
      - $ref: '#/components/schemas/OptionB'