Import issues in modern Node versions due to improperly declared package.json

[fire332]

Describe the bug

import { DateTime } from 'ts-luxon';
         ^^^^^^^^
SyntaxError: The requested module 'ts-luxon' does not provide an export named 'DateTime'

ts-luxon needs to have a properly declared exports field in package.json for Node to use the ESM bundle. Additionally, the exports need to have the correct file extension to avoid incorrect interpretation.

Example:

{
    "type": "commonjs",
    "exports": {
        ".": {
            "types": "./dist/index.d.ts",
            "import": "./dist/ts-luxon.es6.mjs", // NOTE: .mjs file extension
            "default": "./dist/ts-luxon.umd.js" // NOTE: interpreted as commonjs due to `type` field
        }
    }
}

Note that the example has this issue.
See: https://publint.dev/ts-luxon@4.5.2

To Reproduce
https://stackblitz.com/edit/stackblitz-starters-gpzsez?file=index.js

Actual vs Expected behavior
No import errors.

Desktop (please complete the following information):

• OS: Windows 11
• Browser: Chrome 125.0.6368.2 (Official Build) dev (64-bit)
• Luxon version: 4.5.2

[tonysamperi]

Now this is a very useful issue!
Thanks mate!
So I could basically release a V5 to fix the package exports. I definitely will!

By the way it's not a bug because this library was mainly intended to work with Typescript and was supposed to work via umd with javascript.

[fire332]

The bug label is auto-added by GitHub and I have no control over the labels.

I also do consider this a bug since with certain server-side rendering implementations, ts-luxon would be directly imported on the server and not processed through a bundler which would mask this issue.

I've actually originally filed this as a Remix bug here: remix-run/remix#9097

[tonysamperi]

Interesting

[tonysamperi]

Working on this finally! Rough times...

[tonysamperi]

Published v 5.0.0-beta.1 (based on 4.6.0 that I published earlier, so we're aligned to the latest luxon developments that they haven't even published yet :D)

The problem would seem solved.

https://stackblitz.com/edit/stackblitz-starters-gulgmw?file=package.json,index.js

Let me do some tests in the afternoon to see if it also solves the "CommonJS" problem in my other application...

Then I can publish the official 5.0.0...but for now you can enjoy this beta.

Thanks again for the help.

[tonysamperi]

@fire332 can I quote you in the thanks section of the readme?

[tonysamperi]

Published v5.0.0

[fire332]

@fire332 can I quote you in the thanks section of the readme?

Sure. Thanks for the update.

[fire332]

Note that the fix in 5.0 still has the issue noted in the example where TS will allow a default import when it doesn't exist in the package.

https://publint.dev/ts-luxon@5.0.0
https://stackblitz.com/edit/stackblitz-starters-y4jgeo?file=index.ts

Note how there are no TS errors in the stackblitz example but Node will complain about the default export not existing.

Explanation of the issue and how to fix: https://github.com/arethetypeswrong/arethetypeswrong.github.io/blob/main/docs/problems/FalseCJS.md

[tonysamperi]

@fire332 ok since it worked in my scenario I needed to have this released.
I actually noticed the "mts" suggestion in the publint.dev but I honestly don't know how to produce it.
From the docs you linked it's not clear, from what I understand it just needs to be there.
If contents are different, there's no mention.

Luckily I don't need another major for this...
It could be a patch release..

Keep you posted.

PS I already published now that I have the green light I'll mention you on next publish 😉

[fire332]

These links may be helpful:

microsoft/TypeScript#54593
arethetypeswrong/arethetypeswrong.github.io#21

[tonysamperi]

@fire332 man I can't do it.
It's simply not possible, at least with rollup probably.
I tried the following, but the result was always "Masquerade as CJS".

1. Outputting to separate dist folders: produced duplicated typings
2. Adding a second tsconfig and running a second typescript bundle
3. Using babel along rollup (didn't even manage to compile, it compiled fine on it's own, but unbundled outputs)

Probably the way would be bundling with Webpack.

I'm closing this for now.

[tonysamperi]

Ok I think I get it. I should rely on CJS.
I don't know why outputting esm modules should be so painful, but even after refactoring the entire build flow with Webpack, there's simply no way of achieving it.
I'm about to release another beta...
Then run a few tests and if stable I will publish 5.1.0 and deprecate all 5.0.x

[fire332]

Mind if I take a crack at it?

EDIT: tbh, it's probably easier to just drop support for the CJS bundle as ts-luxon will either be used directly in Node.js which supports ES modules (even the oldest LTS version), or it'll be used with a bundler which will handle the ESM/CJS interop anyways.

[tonysamperi]

@fire332 I agree that ts-luxon is intended for interop, the point is that I tried everything, including removing the umd bundle and leave it a module...it always resulted in ESM with CJS typings.

If you want to give it a try you're welcome.
I only ask you a favor, let's update in a couple of weeks from now (in the meantime you can fork the repo and play).

There's really something I need to get over with that depended on the refactor being stable.

But I'm open to bump directly to a pure ESM V6 if we find a way to make it working.

Thanks again for your input.