OneOf type generating Record<string,never> despite all types defined

[mattoni]

Description

I have the following definition for an object:

title: StepResourceLocation
type: object
description: Either a details ID or details from where the ID is an identifier for an existing resource and a from is an identifier from a previous step in this pipeline.
oneOf:
  - title: DetailsId
    type: object
    required:
      - id
    properties:
      id:
        type: string
        description: The ID of an existing resource that exists before the pipeline is run.
  - title: DetailsFrom
    type: object
    required:
      - from
    properties:
      from:
        type: object
        description: The stage and step to report on.
        required:
          - step
        properties:
          stage:
            type: string
            description: An identifier for the stage the step being reported on resides in.
          step:
            type: string
            description: An identifier for the step to be reported on.

However, the generated type is:

    /**
     * StepResourceLocation
     * @description Either a details ID or details from where the ID is an identifier for an existing resource and a from is an identifier from a previous step in this pipeline.
     */
    ResourceLocation: Record<string, never> & OneOf<[{
      /** @description The ID of an existing resource that exists before the pipeline is run. */
      id: string;
    }, {
      /** @description The stage and step to report on. */
      from: {
        /** @description An identifier for the stage the step being reported on resides in. */
        stage?: string;
        /** @description An identifier for the step to be reported on. */
        step: string;
      };
    }]>;

I cannot figure out why it's generating Record<string, never> here. This is a pretty straightforward oneOf, and the options are being generated correctly otherwise.

Name	Version
openapi-typescript	6.4.0
Node.js	19.0.0
OS + version	Linux Pop!_OS 22.04 LTS

Reproduction

Run the above through openapi-typescript generator

Expected result

There should be no Record<string,never> as part of this definition.
Checklist

• My OpenAPI schema passes the Redocly validator (npx @redocly/cli@latest lint)
• I’m willing to open a PR (see CONTRIBUTING.md)

[drwpow]

Hm yeah this definitely looks like a bug. Those types aren’t intentional.

[drwpow]

Ah the Record<string, never> is from the parent object having "type": "object" but no properties or additionalProperties of its own declared. Technically-speaking this is correct since the parent schema is declaring it’s both an empty object ("type": "object" with no properties or additionalProperties) as well as oneOf the declared other types. Therefore it is a union intersection of an empty object (Record<string, never>) as well as the other child types.

The OpenAPI spec allows the use of oneOf WITHOUT having to declare a root-level "type". And I’d recommend doing this in general—if using oneOf, don’t declare a root-level type, and instead inherit one of the child types (after all, they are allowed to diverge!)

However, I can’t imagine a scenario where this is actually the intended output, so we can just fix this from happening. Though I think this wouldn’t cause any major issues and is probably ignorable, let’s just generate better types here just in case.

[mattoni]

Fantastic, thank you so much and for your quick fix. Your explanation makes sense, but I think you're right, in practice this would never be the desired result and makes the intended result unavailable.