[7.4.0] Incorrect return types with TanStack Query and fetch

[rminami]

What are the steps to reproduce this issue?

When generating an orval client with v7.4.0 using TanStack Query and fetch, orval emits an invalid return type for the response data.

const {
  data
} = useGetUsers(
  { limit, offset },
  { request: { accessKey }, query: { placeholderData: keepPreviousData } },
);

In v7.3.0, the return type was User[] | undefined, but with v7.4.0 it emits the following type error.

Type '<T>(previousData: T | undefined) => T | undefined' is not assignable to type 'unknown[]'.

Configuration details

The orval config is

import { defineConfig } from "orval";

export default defineConfig({
  exchange: {
    input: {
      target: "openapi.yml",
    },
    output: {
      client: "react-query",
      mode: "tags-split",
      baseUrl: process.env.BASE_URL,
      workspace: "src/lib/api",
      target: "index.ts",
      schemas: "models",
      prettier: true,
      clean: true,
      override: {
        query: {
          useSuspenseQuery: true,
        },
        mutator: {
          path: "../custom-client.ts",
          name: "customRequest",
        },
        useTypeOverInterfaces: true,
      },
    },
    hooks: {
      afterAllFilesWrite: "prettier -w src/lib/api/**/*.ts",
    },
  },
});

and the custom client is

export const customRequest = async <T>(
  config: {
    url: string;
    method: "GET" | "POST" | "PUT" | "DELETE" | "PATCH";
    params?: Record<string, unknown>;
    headers?: Record<string, unknown>;
    data?: unknown;
    responseType?: string;
    signal?: AbortSignal;
  },
  options?: { accessKey: string | undefined },
): Promise<T> => {
  const params = parseParams(config.params);
  const res = await fetch(config.url + params, {
    ...config,
    ...options,
    body: JSON.stringify(config.data),
    headers: {
      ...config.headers,
      ...(options?.accessKey != null
        ? {
            Authorization: `Bearer ${options.accessKey}`,
          }
        : []),
    },
  });
  return await res.json();
};

What versions are you using?

System:
  OS: macOS 15.2
  CPU: (12) arm64 Apple M3 Pro
  Memory: 3.34 GB / 36.00 GB
  Shell: 5.9 - /bin/zsh
npmPackages:
  @tanstack/react-query: ^5.63.0 => 5.63.0
  orval: ^7.4.0 => 7.4.0
  react: ^19.0.0 => 19.0.0
  zod: ^3.24.1 => 3.24.1

[rminami]

Thank you for the quick fix! Confirmed this is no longer an issue in 7.4.1.