Dynamic import ESM based dependency in Typescript CJS based repo

[leszek---]

Runtime

node.js

Runtime version

20.16.0

Module version

25.3.1

Last module version without issue

No response

Used with

No response

Any other relevant information

No response

What are you trying to achieve or the steps to reproduce?

I have CJS based repo written in Typescript which needs to use ESM-only dependency. I do it by dynamically importing that dependency. Code works correctly when run, but fails to compile during test run.

I use lab with typescript option as advised by docs. In my tsconfig.json I use compilerOptions.module: "Node16" to enable native ECMAScript module support (as per Typescript docs). When running test I get

Unexpected token 'export'

Reason is found in typescript.js file, which is used when typescript option is passed. Mentioned line overrides repos tsconfig option and disables possibility to dynamically import ESM dependency. When I comment out that override, code compiles correctly during test run.

I am not sure whether it is a bug or intended behaviour. If it is intended what is designed way to run my scenario?

---

How to reproduce?

package.json

{
  "name": "lab-test",
  "version": "1.0.0",
  "main": "./dist/src/index.js",
  "scripts": {
    "dist": "rm -rf dist && tsc",
    "start": "node ./dist/src/index.js",
    "test": "lab --typescript"
  },
  "files": ["dist", "src"],
  "license": "ISC",
  "devDependencies": {
    "@hapi/code": "^9.0.3",
    "@hapi/lab": "^25.3.1",
    "@types/node": "^20.16.0",
    "typescript": "^5.6.2"
  },
  "dependencies": {
    "p-map": "^7.0.2"
  }
}

tsconfig.json

{
    "compilerOptions": {
      "module": "Node16",
      "moduleResolution": "Node16",
      "target": "ES2023",
      "outDir": "dist/",
      "rootDir": "./",
      "noEmit": false
    },
    "files": ["src/utils.ts", "src/index.ts"]
  }

src/index.ts

import { isPMapImported } from './utils';

isPMapImported();

src/utils.ts

export const isPMapImported = async () => {
  // p-map is ESM only dependency
  const Pmap = (await import('p-map')).default;

  console.log('Is Pmap imported: ', !!Pmap);
}

test/utils.ts

import * as Lab from "@hapi/lab";
import { expect } from "@hapi/code";

import { isPMapImported } from "../src/utils";

const lab = Lab.script();
const { describe, it, before } = lab;
export { lab };

describe("experiment", () => {
  before(() => {});

  it("is p-map imported", async () => {
    await isPMapImported();

    // assertion doesn't matter as compilation error will happen
    expect(true).to.be.true();
  });
});

When running:

• npm run dist && npm run start (runs dist index.js) I get log Is Pmap imported: true
• npm run test I get compilation error

When I comment out line 29 in node_modules/@hap/lab/lib/modules/typescript.js and run npm run test I get log Is Pmap imported: true and test succeeds

What was the result you got?

Compilation error

Failed tests:

  1) experiment is p-map imported:

      Unexpected token 'export'

      at wrapSafe (node:internal/modules/cjs/loader:1281:20)
      at Module._compile (node:internal/modules/cjs/loader:1321:27)
      at Object.require.extensions.<computed> [as .js] (/Users/leszek_pawlega/git/lab-test/node_modules/@hapi/lab/lib/modules/transform.js:41:28)
      at Module.load (node:internal/modules/cjs/loader:1208:32)
      at Function.Module._load (node:internal/modules/cjs/loader:1024:12)
      at Module.require (node:internal/modules/cjs/loader:1233:19)
      at require (node:internal/modules/helpers:179:18)
      at /Users/leszek_pawlega/git/src/isPMapImported.ts:3:17
      at isPMapImported (/Users/leszek_pawlega/git/src/isPMapImported.ts:3:17)
      at /Users/leszek_pawlega/git/test/isPMapImported.ts:14:5
      at Immediate.<anonymous> (/Users/leszek_pawlega/git/lab-test/node_modules/@hapi/lab/lib/runner.js:659:21)

What result did you expect?

Test will pass