With openapi-fetch

openapi-fetch returns { data, error, response } — not a status-discriminated union. Use the adapter to normalize it.

Setup

lib/expect-status.ts

import { createExpectStatus, adapters } from "expect-status";

export const expectStatus = createExpectStatus({
  adapter: adapters.openapiClient,
  fallbackMessage: "Request failed.",
  defaults: {
    401: "Please sign in.",
    "5xx": "Service unavailable.",
  },
});

Basic usage

import createClient from "openapi-fetch";
import type { paths } from "./api/schema";
import { expectStatus } from "@/lib/expect-status";

const client = createClient<paths>({ baseUrl: "https://api.example.com" });

const user = await expectStatus(
  200,
  client.GET("/users/{id}", { params: { path: { id: "1" } } }),
);

POST with dispatch

const org = await expectStatus(
  201,
  client.POST("/orgs", { body: { name: "Acme" } }),
  {
    409: "Organisation already exists.",
    422: "Please check your input.",
  },
);

With TanStack Query

function useUser(id: string) {
  return useQuery({
    queryKey: ["user", id],
    queryFn: () =>
      expectStatus(
        200,
        client.GET("/users/{id}", { params: { path: { id } } }),
      ),
  });
}

function useCreateOrg() {
  return useMutation({
    mutationFn: (data: { name: string }) =>
      expectStatus(201, client.POST("/orgs", { body: data }), {
        409: ({ message }) => ({ error: message }),
        422: "Invalid input.",
      }),
  });
}

SafeResult

const result = await expectStatus(
  200,
  client.GET("/users/{id}", { params: { path: { id } } }),
  { throws: false },
);

if (result.ok) {
  renderUser(result.data);
} else {
  showError(result.error.message);
}

Alternative: manual wrapping

If you don’t want an adapter instance, wrap per-call:

import { expectStatus } from "expect-status";

const { data, error, response } = await client.GET("/users/{id}", {
  params: { path: { id: "1" } },
});

const user = await expectStatus(200, {
  status: response.status,
  body: data ?? error,
});

See also

• openapi-fetch documentation
• With TanStack Query — query and mutation patterns
• Custom Envelope — adapter details