How to return a response as string?

[McMerph]

Sometimes we need to respond with a plain string (e.g. Prometheus Metrics or OpenAPI spec).
I implement custom EndpointsFactory for this:

import {
  createApiResponse,
  createResultHandler,
  EndpointsFactory,
  z,
} from "express-zod-api";
import type { CommonConfig } from "express-zod-api/dist/config-type";
import mime from "mime";

const negativeMime = mime.getType("txt") ?? "text/plain";

export const getTextEndpointsFactory = (
  config: CommonConfig,
  positiveMime: string
) =>
  new EndpointsFactory({
    config,
    resultHandler: createResultHandler({
      getPositiveResponse: (output) => createApiResponse(output, positiveMime),
      getNegativeResponse: () => createApiResponse(z.string(), negativeMime),
      handler({ response, error, output, logger }) {
        if (error) {
          response.set("Content-Type", negativeMime).status(500).end();
          logger.error(error);
          return;
        }

        response.set("Content-Type", positiveMime).status(200).end(output);
      },
    }),
  });

But if I try to use it like this:

export const getStringEndpoint = getTextEndpointsFactory(
  config,
  mime.getType("txt") ?? "text/plain"
).build({
  method: "get",
  input: z.object({}),
  output: z.string(),
  async handler() {
    return "whatever";
  },
});

I get a tsc error:

error TS2322: Type 'ZodString' is not assignable to type 'IOSchema<any>'.
  Type 'ZodString' is missing the following properties from type 'ZodEffects<ZodObject<any, any, ZodTypeAny, { [x: string]: any; }, { [x: string]: any; }> | ZodEffects<ZodObject<any, any, ZodTypeAny, { [x: string]: any; }, { [x: string]: any; }> | ZodEffects<...>, { ...; }, { ...; }>, { ...; }, { ...; }>': innerType, sourceType

Is it expected?

[RobinTail]

Is it expected?

Yes. On the level of middlewares and endpoints you can only operate objects.
However, the final response is the duty of ResultHandler.

You need a custom ResultHandler.
Check out the documentation and file download/streaming example in this repo.
It exactly responds with a string, @McMerph