Missing nillable value in generated record field when object property has oneOf with $ref and nullable fields

[Nuvindu]

Description

When the OpenAPI spec has the following, the generated type should properly reflect the oneOf schema with $ref and nullable by mapping it to the specific referenced type with a nullable modifier (repository? in this case).

"pull-request-simple": {
  "title": "Pull Request Simple",
  "description": "Pull Request Simple",
  "type": "object",
  "properties": {
    "head": {
      "type": "object",
      "properties": {
        "repo": {
          "oneOf": [
            {
              "$ref": "#/components/schemas/repository"
            },
            {
              "nullable": true
            }
          ]
        }
      }
    }
  }
}

In this case, the generated type for the property repo should be,

public type pullrequestsimple_base record {
    repository? repo;
};

However, the tool generates the following type instead,

public type pullrequestsimple_base record {
    anydata repo;
};

Steps to Reproduce

1. Extract the content from the following json content
   https://github.com/ballerina-platform/module-ballerinax-github/blob/master/docs/spec/openapi.json

2. Generate the files using the following command

   bal openapi -i openapi.json --mode client --client-methods resource

Version

2201.10.0

Environment Details (with versions)

No response

[TharmiganK]

Schema to reproduce the issue:

openapi: 3.0.1
info:
  title: Api
  version: 0.0.0
servers:
  - url: "{server}:{port}/api"
    variables:
      server:
        default: http://localhost
      port:
        default: "8080"
paths:
  /path:
    get:
      operationId: getPath
      responses:
        "200":
          description: Ok
          content:
            application/json:
              schema:
                $ref: "#/components/schemas/RecordB"
components:
  schemas:
    RecordA:
      required:
        - name
      type: object
      properties:
        name:
          type: string
    RecordB:
      required:
        - repo
      type: object
      properties:
        repo:
          oneOf:
            - $ref: "#/components/schemas/RecordA"
            - nullable: true

[TharmiganK]

As a workaround you can use allOf in here:

"pull-request-simple": {
  "title": "Pull Request Simple",
  "description": "Pull Request Simple",
  "type": "object",
  "properties": {
    "head": {
      "type": "object",
      "properties": {
        "repo": {
          "allOf": [
            {
              "$ref": "#/components/schemas/repository"
            }
          ],
          "nullable": true
        }
      }
    }
  }
}