ERR_UNKNOWN_FILE_EXTENSION on Node v20.0.0

[septs]

Search Terms

Node, ERR_UNKNOWN_FILE_EXTENSION

Expected Behavior

Fix it

Actual Behavior

see Minimal reproduction

Steps to reproduce the problem

see Minimal reproduction

Minimal reproduction

$ cat example.ts
console.log('example')
$ cat tsconfig.json
{ "ts-node": { "esm": true } }
$ npx ts-node example.ts
TypeError [ERR_UNKNOWN_FILE_EXTENSION]: Unknown file extension ".ts" for /Users/septs/Projects/example/example.ts
    at new NodeError (node:internal/errors:399:5)
    at Object.getFileProtocolModuleFormat [as file:] (node:internal/modules/esm/get_format:99:9)
    at defaultGetFormat (node:internal/modules/esm/get_format:139:38)
    at defaultLoad (node:internal/modules/esm/load:83:20)
    at nextLoad (node:internal/modules/esm/hooks:781:28)
    at load (/Users/septs/.npm/_npx/1bf7c3c15bf47d04/node_modules/ts-node/dist/child/child-loader.js:19:122)
    at nextLoad (node:internal/modules/esm/hooks:781:28)
    at Hooks.load (node:internal/modules/esm/hooks:381:26)
    at handleMessage (node:internal/modules/esm/worker:153:24)
    at checkForMessages (node:internal/modules/esm/worker:102:28) {
  code: 'ERR_UNKNOWN_FILE_EXTENSION'
}

Specifications

• ts-node version: 10.9.1

• node version: 20.0.0

• TypeScript version: 5.0

• tsconfig.json:

  { "ts-node": { "esm": true } }

• package.json:

  {}

• Operating system and version: macOS 13.3.1

[septs]

microsoft/TypeScript#53922

---

Edited by 11/18/2023

Use tsx replace ts-node?

Or use ts-node@beta?

more see https://github.com/privatenumber/tsx, #2077

[csvn]

I have the same issue. I tried using --esm, { "esm": true } and --loader="ts-node/register", but got the ERR_UNKNOWN_FILE_EXTENSION no matter what I tried. Could not get ts-node to run on Node v20 with native ESM modules.

[Jack-Works]

FYI Node 20 has made a breaking change:

Custom ESM loader hooks run on dedicated thread
ESM hooks supplied via loaders (--experimental-loader=foo.mjs) now run in a dedicated thread, isolated from the main thread. This provides a separate scope for loaders and ensures no cross-contamination between loaders and application code.

https://nodejs.org/en/blog/release/v20.0.0

[RobinTail]

+1

The issue also appears when using the specially dedicated ESM runner

$ ts-node-esm file.ts

[manuth]

I went forward and downgraded my node version to lts.
However, doing node --loader ts-node/esm {file} did work for me.

[wibed]

i expirience the same issue on:

# node --version
v18.16.0

EDIT:
my bad, i misinterpreted the gravity of the situation. manually enforcing the loader like this.

{
  "start": "npm run clean && cross-env NODE_ENV=development NODE_OPTIONS=\"--loader=ts-node/esm --trace-warnings\" webpack serve --mode=development --config webpack.config.ts",
}

worked out.

example sourced from here:
webpack/webpack-cli#2458

[RandivCosta]

i expirience the same issue on: Node v20,
I tried: $ node --loader ts-node/esm ./path
It worked for me but getting this warnning:
ExperimentalWarning: Custom ESM Loaders is an experimental feature and might change at any time

[sywesk]

I'd like to add quickly that on windows (at least), doing node --loader ts-node/esm ./path works but with an insanely high CPU usage. Doing a quick npx tsc + node ./build/app.js works perfectly without the performance issue.

[RobinTail]

Yes, node --no-warnings=ExperimentalWarning --loader ts-node/esm file.ts helps to bypass the issue until it's fixed.

[Aenigma]

yeah, I recently upgraded to node 20 and started running with the --loader ts-node/esm parameter but noticed that my memory usage in my application had skyrocketed to 32G before it would die from OOM. I went chasing for a cause because I assumed it was due to a change I made, but downgrading to node 19 lowered memory usage down to around 500M again. I assume this is probably related to the CPU issues @sywesk had.

So I'd recommend people stay off Node 20 until this is fixed if you don't want to have unexpected issues in your runtime.

[phosmium]

This is horrible. It's been such a long time now and this is still unfixed. @blakeembrey

[PrimalZed]

My solution was to use vite-node instead.

[RobinTail]

I'd recommend tsx as alternative, @phosmium && @PrimalZed .
In my experience it works faster than vite-node and it has flawless ESM support right out of the box without any crutches comparing to swc-node.

[felipecrs]

On the other hand, tsx lacks type checking. tsimp may be a better drop-in replacement than tsx.

[jcapogna]

You can do with just node. Instead of node, I'm doing this:

node --no-warnings=ExperimentalWarning --loader ts-node/esm

[DASPRiD]

On the other hand, tsx lacks type checking. tsimp may be a better drop-in replacement than tsx.

So does ts-node when used with swc, which you really want during development. Time-consuming type checking can be done during build and in general in your CI process. Plus your IDE does type checking as well.

[RobinTail]

On the other hand, tsx lacks type checking.

you can do tsc --noEmit for checking types before execution, but I find types checking more suitable for the testing scope, not for execution of something, @felipecrs

[felipecrs]

Regardless of preferences, ts-node type checks by default and therefore tsimp is a better drop-in replacement to ts-node than tsx since it behaves the same as ts-node by default (I'm not taking into account when used with swc).

If you don't need type checking, then go with tsx of course.

But, for example, my use case needs type checking when executing the application.

[carlos-menezes]

tsx also offers no support for emitDecoratorMetadata, which doesn't bide well for any libraries that need reflect-metadata (e.g. TypeORM).

[Lodjuret2001]

I got my "npm run start" script to work with nodemon this way if this helps anyone:

"start": "nodemon --exec node --no-warnings=ExperimentalWarning --loader ts-node/esm src/server.ts"

Replace "src/server.ts" with the path to the file you want to execute.

[mausam-digital]

My solution was to use vite-node instead.

Awesome this was the easiest workaround, instead of reading all of this useless technical mumbo-jumbo discussion.

[Jamyth]

How can I specify the tsconfig when using

node --loader ts-node/esm ./myscript.mts

[felipecrs]

This issue may be a good excuse to try Deno or Bun instead, btw.

[basselalsayed]

In the end I went with tsx, 0 config and having a separate typecheck command is what I was used to before so not a big deal