Nullable and Non-Nullable versions of a field

[awalsh-broadsoft]

Q	A
Bug or feature request?	Unsure
Which Swagger/OpenAPI version?	3.0.0
Which Swagger-UI version?	3.7
How did you install Swagger-UI?	Tomcat
Which browser & version?	Chrome
Which operating system?	Windows 7 Pro

Demonstration API definition

So previously we were using Json Schema and have recently begun migrating to Open API. There's a particular quirk of our implementation that I'm having trouble porting over.
So what we had sometimes for certain fields would be a non-nullable version of the field (the basic field) and a nullable version of the field. It looked somewhat like this:

"definitions": {
  "DescriptionField": {
    "title": "Book Description",
    "type": "string",
    "maxLength": 10
  },
...
  "NullableDescriptionField": {
    "oneOf": [
      {
        "$ref": "#/definitions/DescriptionField"
      },
      {
        "type": "null"
      }
    ]
  }
}

We're hoping to port this over, but I think the syntax changes enough that we don't have the same functionality.

An implementation I've considered looks like this:

"definitions": {
  "DescriptionField": {
    "title": "Book Description",
    "type": "string",
    "maxLength": 10
  },
...
  "NullableDescriptionField": {
    "allOf": [
      {
        "$ref": "#/definitions/DescriptionField"
      },
      {
        "nullable": true
      }
    ]
  }
}

However, I think there might be a problem with this implementation. I think that because "nullable" defaults to false, that a field couldn't possibly match both schemas, because this would essentially be saying that a matching schema is both nullable = true and nullable = false. Can anyone confirm whether I'm correct in thinking that the above example doesn't work?

Are there any recommendations for how to get nullable versions of fields within Open API 3.0.0?

[hkosova]

According to the comments here and here, nullable needs to be outside of allOf:

  "NullableDescriptionField": {
    "nullable": true,
    "allOf": [
      {
        "$ref": "#/definitions/DescriptionField"
      }
    ]
  }

[awalsh-broadsoft]

Thank you. I think that clears things up for me.

[webron]

Closing as @hkosova provided the solution.