Webpack can't split parts of a single module (e.g. rollup bundle from a dependency) into separate chunks?

[jedwards1211]

Bug report

What is the current behavior?

Forgive me if I've misconfigured something, but it seems like if I import {Toggle} from 'react-powerplug' in chunk A and import {Interval} from 'react-powerplug' in chunk B, all of the react-powerplug code winds up in chunk A, because react-powerplug exports a single rollup bundled js module.

If the current behavior is a bug, please provide the steps to reproduce.

https://github.com/jedwards1211/webpack-code-splitting-issue
just clone, yarn install and run webpack. The output dist/main.js will contain all of the code being used from react-powerplug; the dist/1.js chunk imports Interval from main.js.

Here is what the relevant code looks like:

src/index.js

import {Toggle} from 'react-powerplug'
console.log(Toggle)

import('./chunk-b')

The output dist/main.js on my machine contained all of the code I used from react-powerplug, whereas dist/1.js just imports Interval from main.js:

(window.webpackJsonp=window.webpackJsonp||[]).push([[1],{3:function(o,n,s){"use strict";s.r(n);var w=s(1);console.log(w.a)}}]);

src/chunk-b.js

import {Interval} from 'react-powerplug'
console.log(Interval)

What is the expected behavior?

Code for react-powerplug's Toggle winds up in main.js, and code for Interval winds up in 1.js.

Given that it's becoming popular to release packages as rollup bundles, I want to make sure webpack will be able to include part of that rollup bundle in one chunk, and another part of the bundle in another.

Other relevant information:
webpack version: 4.16.2
Node.js version: 8
Operating System: macOS

[jedwards1211]

I'm going to close this as basically a duplicate of #7782