Differing default exports

[probins]

I'm using several functions from Turfjs, a library of functions for manipulating GeoJSON files. With most of them, I can just do, for example:
import lineSplit from "https://jspm.dev/@turf/line-split";
and then lineSplit(...)
but with
import nearest from "https://jspm.dev/@turf/nearest-point-on-line";
I cannot do nearest(...), but have to do nearest.default(...).

Is this expected behaviour, and if so why?

[guybedford]

This is exactly the standard interop problem.

This edge case applies only for modules that export both an __esModule property and default export. This is a relatively rare edge case since roughly 10% of packages have an __esModule property, and less than 10% of those also have a default export.

jspm has gone the other way to Webpack and RollupJS on this one specific edge case to instead follow Node.js semantics which are more well-defined.

You can read more about the strict Node.js interop semantics here - https://nodejs.org/dist/latest-v15.x/docs/api/esm.html#esm_commonjs_namespaces.

If you want to write you import in a way that works with any bundler for this edge case, write:

import _nearest from "https://jspm.dev/@turf/nearest-point-on-line";
const nearest = _nearest.default || _nearest;

[probins]

ok. I did notice that the package.json was set up differently, and assumed it was something to do with that.

Thanks for the prompt response.

[guybedford]

Sure, and if you'd like a beta invite just ping me.

[teohhanhui]

import _nearest from "https://jspm.dev/@turf/nearest-point-on-line";
const nearest = _nearest.default || _nearest;

That's not an elegant solution as it pushes the burden onto the consumer of the module.

What would be the recommended way to fix this on the module side? In my case, it's https://github.com/staltz/xstream/blob/v11.14.0/dist/xstream.js which is apparently generated by https://www.npmjs.com/package/babel-plugin-transform-es2015-modules-umd

jspm sandbox

[guybedford]

The module.exports.default value is exactly what is being defined, see https://github.com/staltz/xstream/blob/v11.14.0/dist/xstream.js#L1527.

If you are interested in why this is the case, read the interop issue here - rollup/plugins#635.