TypeScript module "NodeNext" does not resolve `index.d.ts` from CJS modules

[AndrewLeedham]

Bug Report

🔎 Search Terms

NodeNext, esm, CJS, cli-spinners

🕗 Version & Regression Information

• This only occurs in nightly builds.
• I was unable to test this on prior versions because nodenext is only supported in the nightly versions.

⏯ Playground Link

From what I can tell you can't install npm modules in the playground, so I made a repro on StackBlitz: https://stackblitz.com/edit/node-opvt9e?file=index.ts run npm run typecheck in the console to see the issue.

💻 Code

import spinners from 'cli-spinners';

console.log(spinners);

🙁 Actual behavior

TypeScript cannot find the typings for cli-spinners which is a CJS module. It does not use a main or exports or types field in the package.json, it just includes a index.js and index.d.ts file.

index.ts:1:22 - error TS2307: Cannot find module 'cli-spinners' or its corresponding type declarations.

1 import spinners from 'cli-spinners';
 ~~~~~~~~~~~~~~


Found 1 error in index.ts:1

🙂 Expected behavior

New NodeNext module behaviour to import CJS as it used to. E.g looking at index.d.ts if there is no main field. https://www.typescriptlang.org/docs/handbook/module-resolution.html#how-typescript-resolves-modules

👪 Related

• Missing main field sindresorhus/cli-spinners#61
• Concerns with TypeScript 4.5's Node 12+ ESM Support #46452

[weswigham]

Huh, I didn't realize we were relying on the directory lookup behavior to fallback to find the main index.js if it wasn't explicitly listed. Shouldn't be too hard to fix.

[weswigham]

Hm, it's a little bit more complicated than that - looks like node doesn't assume a index.js main for packages found via relative imports, but does for those found via nonrelative imports. (Even if both would conceptually look at the same package file under normal cjs rules!) That's... a headache.

[weswigham]

I've opened both #47854 with a fix for this to match node's current behavior, and nodejs/node#41940 to get some kind of discussion about node surprising esm resolver behavior when importing packages via relative paths.

[wight554]

Hi, don't know if I should open new issue, so decided to report here
I've tried to switch my project to TS 4.7 with new module: nodenext and some libraries I use fail to find type declarations, here's the list:
https://github.com/facebookexperimental/Recoil
https://github.com/preactjs/preact (+ preact/hooks)
https://github.com/developit/htm
Currently I was able to shim those by declaring local module and importing type declarations from node_modules, like this

declare module "preact" {
 export * from 'node_modules/preact/src/index.js'
}

I'd like to open issues in corresponding libraries, to fix it properly
Is there any doc/issue I can use for reference, so It'd be easier to fix those by library maintainers?

Upd. fixed in preact master and it's now clear for me what to do
preactjs/preact#3513