ESM loader not working with transpileOnly flag.

[thetutlage]

Using the ESM loader without transpileOnly works fine, but breaks when using transpileOnly. Here's the error.

TSError: ⨯ Unable to compile TypeScript:
error TS4124: Compiler option 'module' of value 'nodenext' is unstable. Use nightly TypeScript to silence this error. Try updating with 'npm install -D typescript@next'.

I understand that the error comes from TypeScript asking to install the @next version. However, I am little confused why disabling transpileOnly makes it work? Is there something I am not aware of?

• ts-node: ^10.7.0
• typescript: ^4.6.3

Following is the tsconfig.json file.

{
  "compilerOptions": {
    "target": "ES2020",
    "module": "NodeNext",
    "strict": true,
    "outDir": "./build",
    "esModuleInterop": true,
    "skipLibCheck": true,
    "noImplicitAny": false,
    "forceConsistentCasingInFileNames": true
  },
  "include": ["./**/*"],
  "exclude": ["./node_modules", "./build"],
  "ts-node": {
    "transpileOnly": true
  }
}

You can reproduce the issue by cloning this repo. https://github.com/thetutlage/ts-node-esm-transpile-only

• Clone the repo
• Run npm install
• And then run npm start

[cspotcode]

I'm guessing that tsc always raises that error when it is used with your configuration. Note that using a different tsconfig, or using a different version of typescript, may obviously change things. Those changes would not be caused by ts-node.

You're probably hitting an issue where ts-node is somehow omitting that error in one code path and not another. This might be a ts-node quirk, but I believe the key takeaway is this: your TypeScript configuration raises this error, and any time the error is not there, you're simply getting lucky. This behavior should not be depended upon. You are getting that error for a reason, and you should read what it says and change your configuration accordingly.

If you want a way to suppress individual diagnostic codes in ts-node, we do have an option for that: ignoreDiagnostics
https://typestrong.org/ts-node/docs/options#ignorediagnostics

[thetutlage]

You are getting that error for a reason, and you should read what it says and change your configuration accordingly

I did read it :) I think you missed the point of why I created the thread

time the error is not there, you're simply getting lucky

🤷🏻‍♂️. Heard for the first time that we can even try our luck with compilers.

Anyways, I know that TypeScript gives the error, but ts-node doesn't, was not something I was expecting

[cspotcode]

Ok, you are wanting ts-node to always raise that error, and it might be a bug that ts-node is somehow suppressing it.

I haven't looked at the relevant code in a while, but when typechecking, we only throw errors for diagnostics that happen within the file being require()d or imported. #853 Perhaps that is related?

[thetutlage]

Yup, exactly, that is what I was looking for :)