Make the generation of unknown types for undefined spec configurable

[jmechevarria]

Description

This is similar, but not quite the same, to #820.

Spec excerpt:

paths:
  /login:
    post:
      operationId: loginMethod
      responses:
        200:
          description: OK
      requestBody:
        content:
          application/json:
            schema:
              $ref: "#/components/schemas/LoginRequest"

Generated TS relating to the response body:

// types.gen.ts
export type LoginMethodResponse = unknown;

In this case, if I don't define anything for the response body, it still gets generated as an unknown type. The name of this type is inferred from the operationId field, eg:

operationId: loginMethod -> LoginMethodResponse

This is unexpected behavior for me, after switching from openapi-typescript-codegen.

Still, it might be by design now, which is why I'm not reporting a bug, but instead asking for the possibility to make it configurable; thus allowing the developer to choose NOT to generate a type at all (even void would be preferable here).

Thanks

[mrlubos]

Hey @jmechevarria, what's the impact of this change?

[jmechevarria]

Hey @mrlubos

1. Not having unnecessary unknown types around 🍃
2. Consistency with long-standing working behavior 👴
3. Keeping your non-paying customers happy 😃

[peppescg]

I have the same issue using hey-api/client-fetch, the body type is body?: RequestInit['body'] | Record<string, unknown> | Array<Record<string, unknown>> | Array<unknown> | number; but from my generated type I have body: unknown so a mismmatch.

Argument of type '{ url: string; headers?: RequestInit["headers"] | Record<string, string | number | boolean | (string | number | boolean)[] | null | undefined | unknown>; method?: "CONNECT" | "DELETE" | "GET" | "HEAD" | "OPTIONS" | "PATCH" | "POST" | "PUT" | "TRACE"; ... 22 more ...; body: v1CreateUserRequest; }' is not assignable to parameter of type 'Omit<RequestOptionsBase<ThrowOnError>, "method">'.
  Types of property 'body' are incompatible.
    Type 'unknown' is not assignable to type 'number | Record<string, unknown> | BodyInit | Record<string, unknown>[] | unknown[] | null | undefined'.ts(2345)

---

I would extend the types in config openapi-ts.config.ts, something like that, where the user can define is own body default type overriding unknown

type EmptyBody = {}
...
requestBody: {
      default: EmptyBody, 
    },

other options could be replace the empty body with RequestInit['body'] | Record<string, unknown> | Array<Record<string, unknown>> | Array<unknown> | number the same used on client-fetch or as last option any if you want to match the axios too,

[mrlubos]

The original issue will be fixed in the new parser. In fact it's fixed already, but more work needs to happen before it's quite ready for you. If you'd like the other issue resolved after that, please open a new ticket.