How can I use "exports" in package.json for nested submodules and TypeScript?

Question

I want to take advantage of the new-ish "exports" feature of Node.js/package.json so that I can do the following:

"exports": {
  ".": "./dist/index.js",
  "./foo": "./dist/path/to/foo.js"
}

and users can do the following:

import { foo } from 'my-package/foo';

TypeScript 4.5 should support the "exports" field, yet it does not seem to work. I am building a simple package using TS 4.5.2, and I am consuming that package in a project using TS 4.5.2. I have looked at other SO questions and this GitHub thread and this bug report but can't seem to find a consensus on the issue and whether it should work today.

I am still able to import using the more verbose syntax:

import { foo } from 'my-package/dist/path/to/foo.js';

I have also tried the object notation for exports, to no avail:

"exports": {
  ".": { "require": "./dist/index.js", "import": "./dist/index.js" },
  "./foo": { "require": "./dist/path/to/foo.js", "import": "./dist/path/to/foo.js" }
}

Is this feature ready to be used with TypeScript projects today? If yes, what am I missing? Specifics about tsconfig would be useful for both the source project and consuming project. The TS compiler complains about node12/nodenext being used for either the module or moduleResolution fields (I am definitely using TS 4.5.2).

Answer 1

Typescript 4.7 FTW! Here's the breakdown:

• Node.js has supported exports since v12.7.0 (Jul. 2019)

  When I asked this question (Dec. 2021), NodeJS had supported the exports field for nearly 2.5 years. It seemed reasonable to assume that Typescript supported it.

• The latest version of TypeScript at that time (4.5) did not support the exports field.

  This was particularly confusing because the TS 4.5 beta announcement said that it would supportpackage.json exports.

• Typescript 4.7 (Jun. 2022) finally supported package.json exports

• Using typesVersions in package.json is not the solution

  Several people suggested using typesVersions - but that's a completely separate feature which is specific to TypeScript only (read more about it here). The exports field in package.json is a feature of node and should work with any npm module.

So, if you have a Typescript project and you want to be able to import a package which uses package.json "exports", you will need to do the following:

• Your TypeScript project must be using TS v4.7 or later
• Your tsconfig should be using moduleResolution of node16 or nodenext.
  • You don't have to set moduleResultion if you are using module with a value of CommonJS, ES2015, ES6, ES2020, or ESNEXT