"type": "object" With No Addtional Properties Generates Object Allowing Any Properties of Type Unknown

[buffalom]

Description

For a schema with "additionalProperties": false, the generator produces an object that allows any properties with type unknown:

export type ProductA = {
  [key: string]: unknown;
};

In my use case (OpenAPI spec in Stackblitz in swagger-usecase.json), this leads to issues where a type extends another type with any properties:

export type Product = {
    $type: string;
};

export type ProductA = Product & {
    [key: string]: unknown;
};

export type ProductB = Product & {
    otherProperty: string;
};

Instead, I would expect "additionalProperties": false to generate the following:

export type ProductA = {
  [key: string]: never;
};

That way, checks like 'otherProperty' in product would actually work and narrow down the type.

However, I am unsure if this would work in all cases, or if unknown is correct in some cases.

Reproducible example or configuration

https://stackblitz.com/edit/hey-api-openapi-ts-additional-properties-bug-repro?file=src%2Fclient%2Ftypes.gen.ts&view=editor

OpenAPI specification (optional)

{
  "openapi": "3.0.1",
  "info": {
    "title": "Test",
    "version": "v1"
  },
  "components": {
    "schemas": {
      "ProductA": {
        "allOf": [
          {
            "type": "object",
            "additionalProperties": false
          }
        ]
      }
    }
  }
}

System information (optional)

"@hey-api/openapi-ts": "0.53.11"

[stackblitz]

Start a new pull request in StackBlitz Codeflow.

• hey-api-openapi-ts-additional-properties-bug-repro (Open reproduction)

[mrlubos]

Thanks @buffalom, added to the parser milestone and will be addressed there!