Interface 'Window' cannot simultaneously extend types 'GlobalFetch' and 'WindowOrWorkerGlobalScope'. Named property 'fetch' of types 'GlobalFetch' and 'WindowOrWorkerGlobalScope' are not identical.

[fmvilas]

Hi! I'm using apollo-server with Typescript, and it raises the following error:

node_modules/apollo-env/lib/global-fetch.d.ts:1:1 - error TS6200: Definitions of the following identifiers conflict with those in another file: RequestInfo, Headers, HeadersInit, Body, Request, RequestInit, RequestMode, RequestCredentials, RequestCache, RequestRedirect, ReferrerPolicy, Response, ResponseInit, BodyInit, URLSearchParams

1 declare function fetch(
  ~~~~~~~

  node_modules/typescript/lib/lib.dom.d.ts:25:1
    25 interface Account {
       ~~~~~~~~~
    Conflicts are in this file.

node_modules/typescript/lib/lib.dom.d.ts:25:1 - error TS6200: Definitions of the following identifiers conflict with those in another file: RequestInfo, Headers, HeadersInit, Body, Request, RequestInit, RequestMode, RequestCredentials, RequestCache, RequestRedirect, ReferrerPolicy, Response, ResponseInit, BodyInit, URLSearchParams

25 interface Account {
   ~~~~~~~~~

  node_modules/apollo-env/lib/global-fetch.d.ts:1:1
    1 declare function fetch(
      ~~~~~~~
    Conflicts are in this file.

node_modules/typescript/lib/lib.dom.d.ts:16316:11 - error TS2320: Interface 'Window' cannot simultaneously extend types 'GlobalFetch' and 'WindowOrWorkerGlobalScope'.
  Named property 'fetch' of types 'GlobalFetch' and 'WindowOrWorkerGlobalScope' are not identical.

16316 interface Window extends EventTarget, WindowTimers, WindowSessionStorage, WindowLocalStorage, WindowConsole, GlobalEventHandlers, IDBEnvironment, WindowBase64, GlobalFetch, WindowOrWorkerGlobalScope, WindowEventHandlers {
                ~~~~~~

It looks like it's related with a change you did 3 days ago in apollo-env but can't confirm this is the real issue.

How to reproduce the error?

Just create a simple project using apollo-server and typescript, and you'll face it when running tsc.

Edit: You can find a sample here: https://github.com/fmvilas/apollo-ts-bug.

Hope it helps!
Thanks!

[fmvilas]

Just in case it helps, I found that commenting the following lines in apollo-env/lib/global-fetch.d.ts, fixes the problem:

// declare function fetch(
//   input?: RequestInfo,
//   init?: RequestInit
// ): Promise<Response>;
//
// declare interface GlobalFetch {
//   fetch(input: RequestInfo, init?: RequestInit): Promise<Response>;
// }

// type RequestInfo = import("./fetch").RequestInfo;
// type Headers = import("./fetch").Headers;
// type HeadersInit = import("./fetch").HeadersInit;
// type Body = import("./fetch").Body;
// type Request = import("./fetch").Request;
type RequestAgent = import("./fetch").RequestAgent;
// type RequestInit = import("./fetch").RequestInit;
// type RequestMode = import("./fetch").RequestMode;
// type RequestCredentials = import("./fetch").RequestCredentials;
// type RequestCache = import("./fetch").RequestCache;
// type RequestRedirect = import("./fetch").RequestRedirect;
// type ReferrerPolicy = import("./fetch").ReferrerPolicy;
// type Response = import("./fetch").Response;
// type ResponseInit = import("./fetch").ResponseInit;
// type BodyInit = import("./fetch").BodyInit;
// type URLSearchParams = import("./url").URLSearchParams;
type URLSearchParamsInit = import("./url").URLSearchParamsInit;

Sorry that I can't help further, I don't really have enough context on how everything is built.

[fmvilas]

Updated the description with a minimal example that reproduces the error.