Handling of nullable for $ref in OpenAPI 3.0

I have an API that needs to differentiate between properties that are T | null and T | undefined. It looks like using nullable works for basic types but is ignored for $ref:

schemas:
  TestObject:
    type: object
    properties:
      stringMaybeUndefined:
        type: string
      stringMaybeNullA:
        type: string
        nullable: true
      stringMaybeNullB:
        anyOf:
        - type: string
        nullable: true
      otherObjectMaybeUndefined:
        $ref: "#/components/schemas/OtherObject"
      otherObjectMaybeNullA:
        $ref: "#/components/schemas/OtherObject"
        nullable: true
      otherObjectMaybeNullB:
        anyOf:
        - $ref: "#/components/schemas/OtherObject"
        nullable: true
    required:
    - stringMaybeNullA
    - stringMaybeNullB
    - otherObjectMaybeNullA
    - otherObjectMaybeNullB

  OtherObject:
    type: object

Generates:

export interface TestObject {
  stringMaybeUndefined?: string;
  stringMaybeNullA?: string | null;
  stringMaybeNullB?: string;
  otherObjectMaybeUndefined?: OtherObject;
  otherObjectMaybeNullA?: OtherObject;
  otherObjectMaybeNullB?: OtherObject;
}

Note: The OpenAPI 3.1 syntax

oneOf:
- $ref: "#/components/schemas/OtherObject"
- type: 'null'

works, but I’m forced to use OpenAPI 3.0 because of constraints from other tooling.

Can this be achieved somehow?

Edit, relevant resources:

• https://github.com/OAI/OpenAPI-Specification/issues/1368
• https://github.com/OAI/OpenAPI-Specification/blob/master/proposals/003_Clarify-Nullable.md

If I interpret these (long) discussions correctly, at least the allOf wrapping should work?

[js2me]

Should be fixed in release 1.6.3
If someone still have same problems, please reopen issue and attach part of swagger schema

[bluenote10]

Looks good, thanks for the super fast maintenance!