[BUG][C++][QT5] OneOf, AnyOf and AllOf Handling Erroneous

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?
• 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

Run the supplied OpenAPI declaration with the cpp-qt5-client generator command, then inspect the generated SchemaAllOf.h, SchemaOneOf.h, and SchemaAnyOf.h files. Compare the handling of all listed composition members and verify that the generated client includes every referenced schema and represents the compositions correctly.