.mjs node module not working after eject

[Kingdutch]

Is this a bug report?

Yes

Can you also reproduce the problem with npm 4.x?

Unsure, using yarn 0.27.5

Which terms did you search for in User Guide?

webkit, constructor

Uncaught TypeError: __WEBPACK_IMPORTED_MODULE_1_universal_router___default.a is not a constructor

Environment

1. node -v: v8.2.1
2. npm -v: 5.3.0
3. yarn --version (if you use Yarn): 0.27.5
4. npm ls react-scripts (if you haven’t ejected): [ejected]

Then, specify:

1. Operating system: Mac OS X High Sierra
2. Browser and version (if relevant):
   Chrome Version 62.0.3202.94 (Official Build) (64-bit)

Steps to Reproduce

(Write your steps here:)

1. Use create-react-app to create a new react app
2. Eject the react app
3. Install "Universal Router" using yarn (yarn add universal-router)
4. Add the following lines to your src/index.js

import UniversalRouter from 'universal-router';
console.log(UniversalRouter);
const router = new UniversalRouter([]);

Expected Behavior

The console output should show that UniversalRouter is a proper constructor function and no errors should occur.

Actual Behavior

The console outputs /static/media/browser.99d6d764.mjs and the following error is shown:
TypeError: __WEBPACK_IMPORTED_MODULE_1_universal_router___default.a is not a constructor

Possible fix

I found that the following fixed this for me:
On line 201 of the generated webpack.config.dev.js replace:
exclude: [/\.js$/, /\.html$/, /\.json$/],
with
exclude: [/\.m?js$/, /\.html$/, /\.json$/],

This might also need to be done for the .prod version.

[Kingdutch]

Should've mentioned that this was originally implemented in #3237

[Timer]

So does jsx suffer from this as well?

[iansu]

Is anyone working on this? If not then I'd like to look into it.

[Timer]

Go ahead @iansu

[Kingdutch]

Didn't have time to go after this earlier.

If I rename a .js file that I include to a .jsx then I end up with the same error as in my original report. If I then change the m?js to m?jsx? it'll correctly match the extension and parse again and that seems to fix the issue.

[gaearon]

This is out in react-scripts@1.1.0! Please let us know if something doesn’t quite work.
https://github.com/facebookincubator/create-react-app/releases/tag/v1.1.0