Redocly lint fails with an error 'Expected type `object,null` but got `object`.'

[ZyzychO]

Describe the bug

With the following schema in openapi: 3.1.1

    pet:
      title: petapi
      type: object
      description: this is pet api
      properties:
        constructor:
          title: petapi
          type:
            - object
            - 'null'

Redocly CLI lint command fails with an error message: 'Expected type object,null but got object.' If you change the 'type' into 'types', lint is passing.

To Reproduce
Steps to reproduce the behavior:

1. Use the following openapi.yaml file:

openapi: 3.1.1
info:
  title: Pet API
  version: 1.0.0
  description: A simple API for pet-related contracts.

paths:
  /pets:
    get:
      summary: Get pet contract information
      operationId: getPet
      responses:
        '200':
          description: Successful response with pet contract
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/pet'

components:
  schemas:
    pet:
      title: petapi
      type: object
      description: this is pet api
      properties:
        constructor:
          title: petapi
          type:
            - object
            - 'null'

2. Execute Redocly lint command
3. See error

Expected behavior

Lint should pass

Logs

OpenAPI description

Configuration in redocly.yaml file:

extends:
  - minimal

Redocly Version(s)

1.33.0

Front conversations

[tatomyr]

@ZyzychO as an immediate workaround, you can change the schema the following way to eliminate the error (it's an alternative way of describing the same data structure):

    pet:
      title: petapi
      type: object
      description: this is pet api
      properties:
        constructor:
          title: petapi
          oneOf:
            - type: object
            - type: 'null'

If you change the 'type' into 'types', lint is passing.

I believe it doesn't matter how you change the name of that property. Redocly CLI specifically check only for the type property, so the error disappears because there's no such one.

[tatomyr]

It seems that support for that syntax was never implemented.

[adamaltman]

This is a valid syntax we have other users that use it. We should update the priority on this issue. It is particularly common with null and another type since they eliminated nullable in 3.1.

[tatomyr]

@adamaltman I think I already have a fix. Need some time to finish a current task and add more tests.

[adamaltman]

Is the issue specific to

- object
- 'null'

Or also applies to other types combined like the following:

- string
- 'null'

[tatomyr]

The same issue will occur with any schema that uses the array type syntax instead of oneOf. For example, the following will also produce a similar error:

type: 
- string
- number

[RomanHotsiy]

It's p1 or p2 at least.

[RomanHotsiy]

It seems that support for that syntax was never implemented.

This is not correct. It does work and was implemented a while ago. The problem is with the constructor keyword.

I you replace it with anything else it works just fine:

components:
  schemas:
    pet:
      title: petapi
      type: object
      description: this is pet api
      properties:
        constructor2:
          title: petapi
          type:
            - object
            - 'null'