Error: No "exports" main defined in <PATH>/libp2p/package.json

[akp111]

libp2p version: 0.42.2
Node version: 16.0.0
npm version : 7.10.0

I am trying to use this in typescript to test out. The tsconfig.json I am using:

{
  "compilerOptions": {
    "module": "commonjs",
    "declaration": true,
    "removeComments": true,
    "emitDecoratorMetadata": true,
    "experimentalDecorators": true,
    "allowSyntheticDefaultImports": true,
    "target": "es2017",
    "sourceMap": true,
    "outDir": "./dist",
    "baseUrl": "./src",
    "incremental": true,
    "skipLibCheck": true,
    "strictNullChecks": false,
    "noImplicitAny": false,
    "strictBindCallApply": false,
    "forceConsistentCasingInFileNames": false,
    "noFallthroughCasesInSwitch": false
  },
  "ts-node": {
    "transpileOnly": true,
    "files": true,
    "experimentalResolver": true
  }
}

But it gives me the following error while doing :
import { createLibp2p } from 'libp2p'

Error: No "exports" main defined in /Users/ashispradhan/Desktop/Projects/EPNS/push-storage-node/node_modules/libp2p/package.json

[achingbrain]

Your tsconfig.json is set to output CJS and not ESM. Please ensure you have the correct settings for "target" and "module" - see: https://github.com/ipfs/js-ipfs/blob/master/docs/upgrading/v0.62-v0.63.md#typescript-and-esm

[github-actions]

Oops, seems like we needed more information for this issue, please comment with more details or this issue will be closed in 7 days.

[Igx22]

I've created a sample project with a long readme.
It shows all the errors that pop up when I try to use the typescript compiler X libp2p.
https://github.com/Igx22/p2p-test

[github-actions]

Oops, seems like we needed more information for this issue, please comment with more details or this issue will be closed in 7 days.

[github-actions]

This issue was closed because it is missing author input.

[Igx22]

I've added more details here.

One more test case https://github.com/Igx22/p2p-test#option-2-start-compiled-js-from-distsrcindexjs-on-typescript-49

[achingbrain]

I think the fundamental problem here is as you have found, ts-node does not support ESM.

Until it does, the only solution you have, if you must use ts-node, is to have your project export CJS but load libp2p (and any other ESM-only module) either from a .mjs file or from a common js file with a dynamic import.

In your test project, I make the following changes:

// tsconfig.json
{
"compilerOptions": {
    "module": "commonjs",
    // ... other stuff
}

And add a cjs file (I called it index.cjs, you can call it index.js if you remove "type": "module" from your package.json):

// src/index.cjs
async function main () {
  await import('./p2p-discovery.mjs')
}

main().catch(err => {
  console.error(err)
  process.exit(1)
})

Then run it, everything is happy:

% npx ts-node src/index.cjs 
node 1 is listening on:
/ip4/127.0.0.1/tcp/54449/p2p/12D3KooWHaikSqN6i3PVALEVLzCe2uVB7uyRU5n9AAQ29TCF9uWT
/ip4/192.168.1.10/tcp/54449/p2p/12D3KooWHaikSqN6i3PVALEVLzCe2uVB7uyRU5n9AAQ29TCF9uWT
node 2 is listening on:
/ip4/127.0.0.1/tcp/54450/p2p/12D3KooWC85PF1CF68o6HCNEny57bE8kv3rLppPtd4ZRSvuZc9VS
/ip4/192.168.1.10/tcp/54450/p2p/12D3KooWC85PF1CF68o6HCNEny57bE8kv3rLppPtd4ZRSvuZc9VS
Hello p2p world!

[achingbrain]

Actually, having said that, if I rename ./src/index.cjs to ./src/test.ts it breaks:

% npx ts-node ./src/test.ts
Error [ERR_REQUIRE_ESM]: require() of ES Module /Users/alex/test/p2p-test/src/p2p-discovery.mjs not supported.
Instead change the require of /Users/alex/test/p2p-test/src/p2p-discovery.mjs to a dynamic import() which is available in all CommonJS modules.
    at /Users/alex/test/p2p-test/src/index-c.ts:2:40
    at async main (/Users/alex/test/p2p-test/src/index-c.ts:2:5) {
  code: 'ERR_REQUIRE_ESM'
}

The above message means ts-node has transpiled await import('./p2p-discovery.mjs') to await require('./p2p-discovery.mjs') or something similar - which is completely wrong.

The error message even tells me to use import() which is what is in the un-transpiled code.

I think you need to wait until ts-node has its ducks in a row about ESM.

[Igx22]

https://github.com/Igx22/p2p-test/pull/1/files

This fix actually helped.
But now I'm not sure if it's safe to use this in a medium sized established project.
I'll probably try to stick with an older libp2p, a js version.

[achingbrain]

But now I'm not sure if it's safe to use this in a medium sized established project.

What are your concerns around this?

I'll probably try to stick with an older libp2p, a js version.

This is not recommended, newer features and bug fixes will not be ported to older versions.

[Igx22]

What are your concerns around this?

70% of our code base is made up of commonjs / require etc.

This is not recommended, newer features and bug fixes will not be ported to older versions.

Fully agree

[achingbrain]

For CJS codebases it's safe to use dynamic imports, it's less safe to stick on old versions.

Looks like you solved your problem with the ts-node upgrade & extra config though, so I'm going to close this.