Relative .js imports still not resolved to .ts (under Yarn PNP?)

[earshinov]

Search Terms

ts-node, esm, ts-node-esm, yarn-pnp

Expected Behavior

Given:

1. A TypeScript project...
2. ...using ESM...
3. ...and relative imports with extensions (as recommended for ESM)...
4. ...with dependencies managed with Yarn PNP (and its own Node loader registered in runtime)

I shouldn't have problems running this TypeScript code with ts-node:

import { a } from './lib/a.js';

Command (actually a package.json script) being used:

yarn node --loader=ts-node/esm.mjs --loader=./.pnp.loader.mjs -- src/main.ts

Actual Behavior

$ yarn run test
(node:12796) [DEP0180] DeprecationWarning: fs.Stats constructor is deprecated.
(Use `node --trace-deprecation ...` to show where the warning was created)

node:internal/modules/run_main:123
    triggerUncaughtException(
    ^
Error: Qualified path resolution failed: we looked for the following paths, but none could be accessed.

Source path: D:\dev\repro-ts-node-esm-yarn-pnp\src\lib\a.js
Not found: D:\dev\repro-ts-node-esm-yarn-pnp\src\lib\a.js

    at makeError (D:\dev\repro-ts-node-esm-yarn-pnp\.pnp.cjs:5630:34)
    at resolveUnqualified (D:\dev\repro-ts-node-esm-yarn-pnp\.pnp.cjs:7362:13)
    at resolveRequest (D:\dev\repro-ts-node-esm-yarn-pnp\.pnp.cjs:7402:14)
    at Object.resolveRequest (D:\dev\repro-ts-node-esm-yarn-pnp\.pnp.cjs:7458:26)
    at resolve$1 (file:///D:/dev/repro-ts-node-esm-yarn-pnp/.pnp.loader.mjs:2043:21)
    at nextResolve (node:internal/modules/esm/hooks:748:28)
    at Hooks.resolve (node:internal/modules/esm/hooks:240:30)
    at MessagePort.handleMessage (node:internal/modules/esm/worker:199:24)
    at MessagePort.[nodejs.internal.kHybridDispatch] (node:internal/event_target:816:20)
    at MessagePort.<anonymous> (node:internal/per_context/messageport:23:28)

Node.js v22.9.0

Steps to reproduce the problem / Minimal reproduction

Repro project: https://github.com/earshinov/repro-ts-node-esm-yarn-pnp/

The error is seen in the GitHub actions workflow: https://github.com/earshinov/repro-ts-node-esm-yarn-pnp/actions/

Specifications

$ yarn run ts-node -vv
ts-node v10.9.2  # 👈 latest
node v22.9.0
compiler v5.6.3
$ yarn --version
4.5.1

tsconfig.json:

{
  "compilerOptions": {
    "baseUrl": "src",
    "declaration": true,
    "module": "ESNext",
    "moduleResolution": "bundler",
    "noImplicitReturns": true,
    "outDir": "dist",
    "rootDir": "src",
    "skipLibCheck": true,
    "sourceMap": true,
    "strict": true,
    "target": "ESNext"
  },
  "include": [
    "src/**/*.ts"
  ]
}

package.json:

{
  "name": "repro-ts-node-esm-yarn-pnp",
  "private": true,
  "packageManager": "yarn@4.5.1",
  "type": "module",
  "scripts": {
    "test": "yarn node --loader=ts-node/esm.mjs --loader=./.pnp.loader.mjs -- src/main.ts",
    "test-with-custom-resolver": "yarn node --loader=ts-node/esm.mjs --loader=./.pnp.loader.mjs --loader=./helpers/resolve-js2ts.mjs -- src/main.ts"
  },
  "devDependencies": {
    "ts-node": "^10.9.2",
    "typescript": "~5.6"
  }
}

• Operating system and version: Windows 11 Version 2382 (OS Build 22631.4602)
• Running on the host, no WSL

Workaround

Using a dump custom resolver. Command:

yarn node --loader=ts-node/esm.mjs --loader=./.pnp.loader.mjs --loader=./helpers/resolve-js2ts.mjs -- src/main.ts

Custom resolver:

export function resolve(specifier, context, nextResolve) {
  console.log(`resolve-js2ts: ${specifier}`);
  if (!specifier.endsWith('.js')) {
    return nextResolve(specifier, context);
  }
  return Promise.resolve(nextResolve(specifier, context)).catch((err) => {
    return Promise.resolve(nextResolve(specifier.replace(/\.js$/, '.ts'), context)).catch(() => {
      throw err;
    });
  });
}

Output:

$ yarn run test-with-custom-resolver
(node:47096) [DEP0180] DeprecationWarning: fs.Stats constructor is deprecated.
(Use `node --trace-deprecation ...` to show where the warning was created)
resolve-js2ts: file:///D:/dev/repro-ts-node-esm-yarn-pnp/src/main.ts
resolve-js2ts: ./lib/a.js
a

References

#1361 - most relevant piece of information I have found. Judging by the fact that the issue is closed and the relevant pull requests have been merged, it would seem that the problem has been fixed >1 year ago, except it apparently wasn't. Or maybe I'm dumb and there is another trap somewhere (as it usually is when it comes to Node.js, Yarn PNP, TypeScript and ESM).

✨Solution ✨

Do not pass --loader=./.pnp.loader.mjs when running yarn node, yarnpkg/berry#6645 (comment)

[t1bb4r]

@earshinov I don't see this in your tsconfig. Have you tried this setting?

  "ts-node": {
    "experimentalResolver": true,
  }

See https://typestrong.org/ts-node/docs/options#experimentalresolver

[earshinov]

@t1bb4r , Thank you for looking into this. Tried it right now -- doesn't seem to change anything. Also added it to GitHub actions: https://github.com/earshinov/repro-ts-node-esm-yarn-pnp/actions/runs/12697806025/job/35394904259.

package.json:

"scripts": {
    "test-with-experimental-resolver": "TS_NODE_PROJECT=tsconfig.ts-node-experimental-resolver.json yarn node --loader=ts-node/esm.mjs --loader=./.pnp.loader.mjs -- src/main.ts",
}

tsconfig.ts-node-experimental-resolver.json:

{
  "extends": "./tsconfig.json",
  "ts-node": {
    "experimentalResolver": true
  }
}

[kbaba1001]

you need to remove "type": "module", on package.json

[earshinov]

@kbaba1001 , I want my script to be executed as an ESM module, that's the point

[earshinov]

Turned out I incorrectly invoked yarn: when running yarn node, one must not pass --loader=./pnp.loader.mjs additionally. yarnpkg/berry#6645 (comment)