ExperimentalWarning: Import assertions are not a stable feature of the JavaScript language

[zaripych]

Bug description

When I run tsx code.ts I get following output:

➜  esm-loader-warning-repro pnpm tsx code.ts
(node:76711) ExperimentalWarning: Import assertions are not a stable feature of the JavaScript language. Avoid relying on their current behavior and syntax as those might change in a future version of Node.js.
(Use `node --trace-warnings ...` to show where the warning was created)
Hello esm-loader-warning-repro!

I expected:

Hello esm-loader-warning-repro!

I've noticed that we already suppress some warnings in here

Should we suppress this type of warning as well?

Reproduction

I have "type": "module" in my package.json:

{
  "name": "esm-loader-warning-repro",
  "version": "1.0.0",
  "type": "module",
  "dependencies": {
    "tsx": "^3.12.7"
  }
}

code.ts has following content:

import pack from "./package.json";

console.log(`Hello ${pack.name}!`);

I'm using Node 18:

➜  esm-loader-warning-repro pnpm tsx --version
tsx v3.12.7
node v18.16.0

Environment

System:
    OS: macOS 13.2.1
    CPU: (10) arm64 Apple M1 Max
    Memory: 24.08 GB / 64.00 GB
    Shell: 5.8.1 - /bin/zsh
  Binaries:
    Node: 18.16.0 - ~/.nvm/versions/node/v18.16.0/bin/node
    Yarn: 1.22.19 - ~/.nvm/versions/node/v18.16.0/bin/yarn
    npm: 9.5.1 - ~/.nvm/versions/node/v18.16.0/bin/npm
  npmPackages:
    tsx: ^3.12.7 => 3.12.7

Can you work on a fix?

• I’m interested in opening a pull request to address this issue.

[privatenumber]

IIRC they have a new way of making import assertions. Could we use that instead on newer versions of Node.js?

[zaripych]

In my example above, I do not do any assertions explicitly, it's the latest version of the esm-loader that causes the warning.

If we can do something to make the warning go away in the esm-loader then we can take that path. I'm not very familiar with loader API, but ignoring a warning by adding a string to an array seems like an easy fix with low risk.

[ArnaudBarre]

I've been annoyed by this warning so I tried to build a slim tsx version. For the JSON import I provided a loader to that there is not warning not usage of experimental API:

[privatenumber]

The warning was added in nodejs/node#46901 and motivated by nodejs/node#46830 but there is currently no successor to the assert syntax.