Cannot use "cross-undici-fetch" with TypeScript

[pitgrap]

Describe the bug

If I add import { fetch } from "cross-undici-fetch"; to my .ts file, I get the following compile error:

> tsc -v && tsc --build && babel ./src --out-dir ./dist --extensions ".ts,.js"

Version 4.5.5
../../node_modules/.pnpm/cross-undici-fetch@0.1.23/node_modules/cross-undici-fetch/dist/index.d.ts:12:23 - error TS1254: A 'const' initializer in an ambient context must be a string or numeric literal or literal enum reference.

12 declare const _Blob = Blob;
                         ~~~~

../../node_modules/.pnpm/cross-undici-fetch@0.1.23/node_modules/cross-undici-fetch/dist/index.d.ts:13:23 - error TS1254: A 'const' initializer in an ambient context must be a string or numeric literal or literal enum reference.

13 declare const _File = File;

I'm stick to this package, because @graphql-tools/url-loader 7.7.1 has a dependecy to this package. If I want to use cross-fetch instead, it's not working, becauseof error TS2451: Cannot redeclare block-scoped variable '_fetch'. etc.

Environment:

• OS: Linux (WSL)
• package-name...: "cross-undici-fetch": "^0.1.23",
• NodeJS: 16
• Typescript 4.5.5

[JustusNBB]

This issue also comes up when trying to use a GraphQL Mesh SDK (refs ardatan/graphql-mesh#2659 (comment))

To which version can I pin to temporarily fix?

[ardatan]

Please share a live reproduction.

[JustusNBB]

I found a workaround on Stackoverflow, enable skipLibCheck, and the type error goes away:

{
  "extends": "../tsconfig.shared.json",
  "compilerOptions": {
    "skipLibCheck": true
  }
}

https://stackoverflow.com/questions/65543585/a-const-initializer-in-an-ambient-context-must-be-a-string-or-numeric-literal

Then minimum reproduction goes like this:

1. mkdir, cd
2. npm i typescript cross-undici-fetch
3. npx typescript init
4. set tsconfig "skipLibCheck": false <-- without this one there are no issues
5. tsc or navigate into node_modules/cross-undici-fetch/dist/index.d.ts with VSCode to see type issue

[ardatan]

This is not a live reproduction. You can use CodeSandbox or StackBlitz so we can make sure we see the exactly same thing.

[JustusNBB]

This is not a live reproduction. You can use CodeSandbox or StackBlitz so we can make sure we see the exactly same thing.

Oh cmon, this is even better than CodeSandBox or StackBlitz, tried both now and I don't see how they report type issues at all! Debugging is much easier locally with VSCode, and these steps don't take long.

[JustusNBB]

Ok sorry maybe I forgot the testSmth.ts, it only needs to contain the

import { fetch } from "cross-undici-fetch";

mentioned at the beginning, so there is actually something to compile.

[ardatan]

I want a reproduction on a sandbox environment because I don't want to discuss "it doesn't happen on my local".
Even if their IDEs don't report, you can use "tsc" which reports the same TS errors that IDE language servers show

[dotansimha]

Oh cmon, this is even better than CodeSandBox or StackBlitz, tried both now and I don't see how they report type issues at all! Debugging is much easier locally with VSCode, and these steps don't take long.

You are assuming the solution and the issue, and we can't guess what's the actual issue before pinning/reducing it to the bare minimum. tsconfig and TS can behave differently based on many parameters.
I have a 3 TS projects that are using Mesh SDK and cross-undici-fetch and I don't have any issue with that.

If there is an issue, and you know where the issue is - feel free to create a PR to fix it.
If you want us to fix it for you, please share a minimal reproduction.

[JustusNBB]

Yeah thanks. You didn't even try my minimal reproduction ...
I also still need to find out what this flag actually does, and what the actual solution for this is.

So after some more fighting the codesandbox I now have a live reproduction for you even if this is far from being on top of my priorities:

https://codesandbox.io/s/hopeful-nash-zipc1m?file=/tsconfig.json

"skipLibCheck": false /* Skip type checking all .d.ts files. */

try running npm test with skipLibCheck: false|true
(bottom right Terminal top right + button)

[JustusNBB]

@ardatan here is even an idea for a fix #19