Can't use ESM with jsc.paths

[Nickersoft]

Describe the bug

Hey folks,

I've come into a bit of a pickle. Node 19 drops support for es-module-specifier-resolution, which I have been using to support extension-less imports in my ESM codebase.

I realized this makes it impossible for me to continue using jsc.paths in my TypeScript project, as ts files automatically have their extensions removed, yet if I use js as an extension, SWC can't find the path and doesn't transform the import.

Example

"paths": {
    "@my/pkg": ["libs/pkg/src/index.ts"]
}

results in:

import { fn } from 'libs/pkg/src/index';

and

"paths": {
    "@my/pkg": ["libs/pkg/src/index.js"]
}

results in:

import { fn } from '@my/pkg';

Input code

import { fn } from '@my/pkg';

Config

{
  "module": {
    "type": "es6"
  },
  "jsc": {
    "baseUrl": ".",
    "target": "es2020",
    "parser": {
      "syntax": "typescript",
      "decorators": true,
      "importMeta": true
    },
    "transform": {
      "legacyDecorator": true,
      "decoratorMetadata": true
    },
    "keepClassNames": true,
    "paths": {
      "@my/pkg": ["libs/pkg/src/index.ts"],
    }
  }
}

Playground link

No response

Expected behavior

I think that SWC should provide a similar mechanism to how TypeScript supports ESM, where TS files can be imported as JS (i.e. jsc.paths should find and transform the path appropriately).

Better yet, now that you can import ts files in TS, what I really wish is that you could just always use ts extensions for everything and SWC would be smart enough to know to replace them with js in the transpiled code instead of just removing the extension.

Actual behavior

Right now, SWC defaults to removing TS extensions unless you manually import TS files as JS (which luckily TS supports), however, this breaks down when using jsc.paths as described above. Starting in Node 19, this will result in un-runnable code without a custom loader.

Version

1.3.77

Additional context

No response

[Nickersoft]

Hey @kdy1! Excited to see this marked as planned. Curious out of the suggestions above, what approach do you think the SWC project will take here? Or are you still unsure?

[kdy1]

I prefer following the direction of tsc, but I'm not sure if tsc has one. Mainly because I didn't read your comment yet... I need some time 😄

[Nickersoft]

Haha sure thing – regardless, super happy this is getting looked at and let me know if I can help in any way :)

[kdy1]

I think

{
  "module": {
    "type": "es6"
  },
  "jsc": {
    "baseUrl": ".",
    "target": "es2020",
    "parser": {
      "syntax": "typescript",
      "decorators": true,
      "importMeta": true
    },
    "paths": {
      "@my/pkg": ["libs/pkg/src/index.js"],
    }
  }
}

is a better API

[kdy1]

But maybe we need an option to fully qualify index.js even if we can remove it from the import.

[kdy1]

Filed #7861

[swc-bot]

This closed issue has been automatically locked because it had no new activity for a month. If you are running into a similar issue, please create a new issue with the steps to reproduce. Thank you.