How to split a typescript package into multiple submodules?

Question

My newest typescript project is split into different modules and submodules.

My file structure:

package.json
(...)
/src
| /module1
| | index.ts
| | (...)
| | /subModule1
| | | index.ts
| | | (...)
| | /subModule2
|   | index.ts
|   | (...)
| /module2
  | index.ts
  | (...)

Every (sub)module has a index.ts file holding the module's exports.

Now I finally want to publish my package. One should be able to import stuff from the modules in the following way:

import { A } from "package/module1";
import { B, C } from "package/module1/subModule2";

I've already used this syntax on importing stuff from other packages on npm. But I can't find any explanations on how to implement such behavior. I've found some article explaining it for multiple files, but not for multiple modules structured in folders and subfolders.

Continuity

Answer 1

See "Subpath exports" in Node documentation:

• https://nodejs.org/api/packages.html#subpath-exports

Example:

{
  "main": "./main.js",
  "exports": {
    ".": "./main.js",
    "./submodule": "./src/submodule.js"
  }
}

This article may help you with that:

• Node.JS (New) Package.json Exports Field by Thomas Juster

Plus some TypeScript-specific info in this issue on GitHub:

• Support for NodeJS 12.7+ package exports #33079

And since you say that you've already used this syntax on importing stuff from other packages on npm, then you might also take a look at the source code of those packages to see how they do it.

Salesin

Thanks a lot :DD Your answer and this package solved the whole issue :) – Continuity

@Continuity Great to know that I could help and thanks for the link to this package :) – Salesin

I also have this kind of structure but when I import the sub packages typescript doesn't seem to find its declarations. Is there any tip you guys have about that? – Jonathanjonathon

This works, I mean, the loaded modules are available. But wit this syntax, TS(4.7.4) does not recognize it. EDIT: tsconfig.json > "module": "Node16" and "moduleResolution": "Node16" makes it work entirely – Cry

Even with TS 5+ I can only get submodules to work using the typesVersions work around. I've tried the MS syntax referenced in the comment above and the examples in the "Support for NodeJS 12.7+" GitHub issue. Nothing other than typesVersions has any impact at all. – Grith

@Continuity works perfectly thanks to rsp answer and the package you linked ! – Boathouse

It is working for me too, but auto-import doesn't work. I have to import manually. Otherwise it's as if types are invisible until I import them. Any idea why? – Roam