[BUG][Ruby] Using oneOf generated code has unexpected results

Created by: ssteeg-mdsol

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

When a oneOf is used, the generated model only includes one of the possible classes. Using the client, objects for all class types are forced into the same class, even if they're a different class.

In the below example, if the API returns a AuthenticationMonitor MonitorResult object, the generated client forces it into the SmokeTestMonitor class type. This is a problem as it's the incorrect class type and as a result the model attributes are all nil.

Current output for the AuthenticationMonitor MonitorResult object:

...
@items=[#<ClientExample::SmokeTestResult:0x00007fb45220eaa0>]
...

Expected output for the AuthenticationMonitor MonitorResult object:

...
@items=[#<ClientExample::AuthenticationMonitorItems:0x00007fb45220eaa0 @result=true>]
...

openapi-generator version

4.1.0, seems to occur in every 4.x version. Haven't checked previous versions.

OpenAPI declaration file content or url

OpenAPI spec

AuthenticationMonitor and SmokeTestMonitor are the same but the property name inside items is different

openapi: 3.0.2
info:
  title: Example
  version: v1
paths:
  /endpoint:
    get:
      summary: Get All Monitors
      responses:
        '200':
          description: Successful operation.
          content:
            application/json:
              schema:
                type: array
                items:
                  $ref: '#/components/schemas/Monitor'
components:
  schemas:
    Monitor:
      type: object
      properties:
        results:
          $ref: '#/components/schemas/MonitorResults'
    MonitorResults:
      oneOf:
        - $ref: '#/components/schemas/AuthenticationMonitor'
        - $ref: '#/components/schemas/SmokeTestMonitor'
    AuthenticationMonitor:
      type: object
      properties:
        items:
          type: array
          items:
            type: object
            properties:
              result:
                type: boolean
    SmokeTestMonitor:
      type: object
      properties:
        items:
          type: array
          description: Collection of smoke test result checks.
          items:
            type: object
            properties:
              passed:
                type: boolean

Command line used for generation

openapi-generator generate -i <OPENAPI_SPEC> -g ruby -o <TEMP_DIR> -c <CONFIG_PATH>

Steps to reproduce

1. Run the command to generate the Ruby client
2. Look at the

Related issues/PRs

Maybe https://github.com/OpenAPITools/openapi-generator/issues/15 is related, but this issue is more specific to the Ruby client.

Another issue related to oneOf for the Ruby client is the generation of objects within a response schema. If you have the following OpenAPI spec, the class type gets generated as ExampleClient::OneOfsimpleObjectcomplexObject, and that class does not exist.

OpenAPI spec snippet

Here is the spec:

paths:
  /endpoint:
    get:
      summary: Get All Monitors
      responses:
        '200':
          description: Successful operation.
          content:
            application/json:
              schema:
                oneOf:
                  - $ref: '#/components/schemas/simpleObject'
                  - $ref: '#/components/schemas/complexObject'

components:
  schemas:
    simpleObject:
      type: object
      properties:
        simple_property1:
          type: string
    complexObject:
      type: object
      properties:
        complex_property1:
          type: string
        complex_property2:
          type: string

Suggest a fix

In https://github.com/OpenAPITools/openapi-generator/blob/master/modules/openapi-generator/src/main/resources/ruby-client/partial_model_generic.mustache#L49, the generated client only includes one option Array<SmokeTestResult>. I'm not sure about a specific fix, but has there been any Ruby-specific development into this area?