ns prototype is null, but that breaks some things

[joeldenning]

systemjs/src/system-core.js

Line 83 in 0f1161d

const ns = Object.create(null);

Some projects assume that their dependencies have the full object prototype available to them. For example, the popular react-table project does this (see line 7 of react-table.development.js)

This throws an Error when the dependency (in this case react) does not have the Object.prototype methods on it.

Is there any reason not to change that code to be ns = {}, so that the prototype is Object.prototype?

@guybedford thoughts?

[guybedford]

React isn't an ES module though so shouldn't be a namespace - rather it should be used via import React from 'react' as its own default export.

Is this because you are using the named exports extension?

It is very important not to change this - namespaces have an empty prototype by the ECMAScript specification.

[joeldenning]

Yes, I discovered this when talking with someone setting up single-spa. They are using the named-exports extra because that's the easiest way to be able to do import { useState } from 'react';

[guybedford]

I would suggest getting React table to fix this as a bug in that project then - that they are detecting a namespace using a technique that is not spec valid for namespaces.

[bartoszgolebiowski]

I had a serious problem with that
This is my dependency which I am using.

(function (global, factory) {
  typeof exports === 'object' && typeof module !== 'undefined' ? factory(exports, require('react')) :
  typeof define === 'function' && define.amd ? define(['exports', 'react'], factory) :
  (global = global || self, factory(global.ReactQuery = {}, global.React));
}(this, (function (exports, React) { 'use strict';

  React = React && React.hasOwnProperty('default') ? React['default'] : React

The last line couse exception

React variable is Module and does not have hasOwnProperty function.

This is caused because React variable is the module and does not have hasOwnProperty method

this is a screenshot right before the exception accrued.

To solve it I need to invoke this formula at the very beginning before importing react-table

    System.import('react')
      .then(ns => Object.setPrototypeOf(ns, Object.prototype))

[guybedford]

The problem is this bug in Rollup - rollup/rollup#3420 which was released in 1.32.1 - when React table uses that build it will resolve the issue.

I would suggest posting an issue to React table to get a new build out with that release asap.

[joeldenning]

Good catch - I had just verified that rollup does this correctly now with this repl example. It looks react-table isn't yet on 1.32.1 - https://github.com/tannerlinsley/react-table/blob/master/yarn.lock#L6720. I'll create a pull request to upgrade this for them.

[joeldenning]

I have created TanStack/table#2021 to resolve this issue in react-table.