Error "'default' is not exported by <package>" when importing in Svelte file

[Kcnarf]

Describe the bug

Hello,
I made and maintain the d3-voronoi-map package (https://github.com/Kcnarf/d3-voronoi-map). Also, I'm not a Svelte user.

An issue (Kcnarf/d3-voronoi-map#16) reports that the d3-voronoi-map package, when imported with Svelte (at least into svelte.dev), raises the error ERROR 'default' is not exported by https://unpkg.com/d3-array@3.2.0/src/index.js, imported by https://unpkg.com/d3-weighted-voronoi@1.1.3/build/d3-weighted-voronoi.js.

I did some explorations (resumed in Kcnarf/d3-voronoi-map#16 (comment)). For short:

• the error is understandable as the dependency d3-array package has not any default export
• BUT I don't understand why the error is raised as the source code only import {extent as d3Extent} from d3-array, without any default import.

Thanks for your feedbacks/highlights/comments/help.

PS: the severity of this issue is not appropriate, but don't find any good one.

Reproduction

https://svelte.dev/repl/d3847fb950b54cdca2868aaab2bd7872?version=3.49.0

Logs

from Chrome console:

Error: 'default' is not exported by https://unpkg.com/d3-array@3.2.0/src/index.js, imported by https://unpkg.com/d3-weighted-voronoi@1.1.3/build/d3-weighted-voronoi.js
    at R (index.854e7b3c.js:20:1087)
    at ne.error (index.854e7b3c.js:27:87296)
    at ne.traceVariable (index.854e7b3c.js:27:95377)
    at Ga.findVariable (index.854e7b3c.js:27:39925)
    at xe.bind (index.854e7b3c.js:24:32979)
    at Property.bind (index.854e7b3c.js:24:799)
    at ObjectExpression.bind (index.854e7b3c.js:24:785)
    at VariableDeclarator.bind (index.854e7b3c.js:24:799)
    at Wa.bind (index.854e7b3c.js:24:785)
    at Fa.bind (index.854e7b3c.js:24:785)
Kp @ index.854e7b3c.js:59
await in Kp (async)
(anonymous) @ index.854e7b3c.js:59
setTimeout (async)
(anonymous) @ index.854e7b3c.js:59

System Info

Mac OS Monterey 12.4
Chrome Version 104.0.5112.79 (Build officiel) (x86_64)

Severity

blocking an upgrade

[Conduitry]

I'm transferring this to the repo for the REPL.

I haven't really dug into this a ton, but it looks like the code the REPL is getting from your library (https://unpkg.com/d3-weighted-voronoi@1.1.3/build/d3-weighted-voronoi.js) is an UMD built version. The REPL isn't using the ESM version in your package, I'm guessing because you refer to it only as jsnext:main and not as module (https://unpkg.com/d3-weighted-voronoi@1.1.3/package.json).

Neither jsnext:main nor module are official fields in package.json, but the former is older and is mostly deprecated in various tooling in favor of the latter. Exposing pkg.module in your package might help. Updating the REPL to also look at pkg['jsnext:main'] might help. I don't know what might reasonably to done to support loading from the UMD build.

[Kcnarf]

Thanks for your comment.
I'll definitely dig into that direction.

[benmccann]

I would recommend changing from umd to esm if you can:

https://github.com/Kcnarf/d3-weighted-voronoi/blob/1d3684d6292ea314b7a07a65506b363d45d83009/rollup.config.js#L11

This FAQ about packaging may also be helpful to you: https://kit.svelte.dev/faq#packages

[Kcnarf]

@benmccann
thanks for your comment.

I'm currently looking at this cjs/esm/umd and hybrid way of delivering/providing packages.

As the package I'm maintaining is a plugin for the d3.js package/environment (https://d3js.org/, https://github.com/d3/d3), I will follow the same path as d3.js : going from an umd distribution to an esm one (d3/d3#3501). Apparently, this move has been done in mid 2021, and made available in the d3@7.