Top-level await and dynamic imports

[zeen]

I have a relatively straightforward typescript project, that's importing nodejs internal libraries, some yarn-installed JS modules and other typescript files. I'm trying to add dynamic import with top-level await to a file, and struggling to figure out the right tsconfig.

Example code:

import {PassThrough} from 'stream'; // nodejs's built-in stream library
const handlers = [
  await import('A').handler,
  await import('B').handler,
  await import('C').handler,
];

The following two configurations are interesting:

1. With "target": "es2019", "module": "commonjs":

error TS1378: Top-level 'await' expressions are only allowed when the 'module' option is set to 'esnext' or 'system', and the 'target' option is set to 'es2017' or higher.

2. With "target": "es2019", "module": "esnext":

(node:55) Warning: To load an ES module, set "type": "module" in the package.json or use the .mjs extension.
...
import { PassThrough } from 'stream';
^^^^^^

SyntaxError: Cannot use import statement outside a module

I did add "type": "module" to package.json, which seems to have no impact.

Interestingly VSCode doesn't show an error in the editor with (2) config above, only ts-node does.

What am I missing? I'm on Node v15, using ts-node 9.1.1, typescript 4.2.4. Target is es2019 simply because that most closely matched features Node v15 actually supported, I can change versions of anything as needed.

[cspotcode]

Interestingly VSCode doesn't show an error in the editor with (2) config above, only ts-node does.

Remember that VSCode is not transforming nor executing the code, only performing static analysis via the language service.

ts-node is doing 3x more than VSCode:

• running the compiler's static analysis
• transforming .ts into .js
• asking node to execute the in-memory .js

You probably want to use our ESM loader. #1007 has instructions.