Support for union type

[guyariely]

The following schema:

Example:
      type: object
      properties:
        prop:
          type:
            - string
            - number

Will yield the following type:

interface Example {
  prop: unknown;
}

While the appropriate type would be:

interface Example {
  prop: string | number;
} 

It seems a property with more than one type is being treated as unknown.
This is especially apparent when trying to document nullable properties.

Package Version: 6.9.6

[mb21]

That would be great, also when using OpenAPI's oneOf with enum. For example:

openapi: 3.0.3
info:
  title: Sample API
  description: Sample
  version: '1.0'

paths:
  /pets:
    get:
      responses:
        '200':
          description: Pets
          content:
            application/json:
              schema:
                oneOf:
                  - $ref: '#/components/schemas/Cat'
                  - $ref: '#/components/schemas/Dog'
components:
  schemas:
    Dog:
      type: object
      properties:
        kind:
          type: string
          enum: [dog]
    Cat:
      type: object
      properties:
        kind:
          type: string
          enum: [cat]

would generate:

interface Dog {
  kind: 'dog';
}

interface Cat {
  kind: 'cat';
}

type PetsResponse = Dog | Cat

which is a discriminated union.

---

The whole thing would be like openapi-typescript-codegen's --useUnionTypes option.

[DominicBach]

FYI this is not a valid OpenAPI specification, see https://swagger.io/specification/#schema-object

The following properties are taken from the JSON Schema definition but their definitions were adjusted to the OpenAPI Specification.

type - Value MUST be a string. Multiple types via an array are not supported.

The correct way to model this would be

Example:
  type: object
  oneOf:
    - type: object
      properties:
        prop:
          type: string
    - type: object
      properties:
        prop:
          type: number

[mb21]

@DominicBach I updated the snipped to be complete (now it validates) and replaced the confusing double use of type with kind in one place. Please check out the links, hope it makes sense now?

[geirsagberg]

@DominicBach Type arrays are supported in OpenAPI 3.1: https://www.openapis.org/blog/2021/02/16/migrating-from-openapi-3-0-to-3-1-0

[geirsagberg]

I added a PR for nullability that should fix this one as well: #645