_index.mjs may not be resolved for some reason in legacy projects

[fengxinming]

_index.mjs of @babel/runtime@7.13.x may not be resolved for some reason in legacy projects, I would like to recommend babel team to rename _index.mjs to index.es.js, Thanks!

[babel-bot]

Hey @fengxinming! We really appreciate you taking the time to report an issue. The collaborators on this project attempt to help as many people as possible, but we're a limited number of volunteers, so it's possible this won't be addressed swiftly.

If you need any help, or just have general Babel or JavaScript questions, we have a vibrant Slack community that typically always has someone willing to help. You can sign-up here for an invite."

[babel-bot]

Hi @fengxinming! This issue is missing some important information we'll need to be able to reproduce this issue.

Please understand that we receive a high volume of issues, and there are only a limited number of volunteers that help maintain this project. The easier it is for us to decipher an issue with the info provided, the more likely it is that we'll be able to help.

Please make sure you have the following information documented in this ticket:

1. Your Babel configuration (typically from .babelrc or babel.config.js)
2. The current (incorrect) behavior you're seeing
3. The behavior you expect
4. A short, self-contained example

Please provide either a link to the problem via the repl, or if the repl is insufficient, a new and minimal repository with instructions on how to build/replicate the issue.

[afc163]

#12861

[fengxinming]

@afc163 I can not change webpack config for some legacy reason，I wish everything is going well like 7.12.18。

[nicolo-ribaudo]

#12900 shows well what is the problem.

I'm sorry that this update broke your project, but it's a problem in you webpack configuration: .mjs files work in every webpack version, except if your config tells webpack not to make them work.
I have been trying to think about a fix, but if you need this to be resolved soon you should fix it in your webpack config.

In the meantime, you could pin @babel/runtime to ~7.12.0.

[fengxinming]

@nicolo-ribaudo

{
  "resolutions": {
    "@babel/runtime": "7.12.18",
    "@babel/runtime-corejs2": "7.12.18",
    "@babel/runtime-corejs3": "7.12.18"
  },
}

I have locked versions by this way, and the problem is not what you think, and webpack configuration can not be changed in our projects, for some legacy reason those configuration be wrapped like react-scripts, actually those @babel/runtime packages are from dependencies of some third party packages, our projects still use babel6.

[JLHwung]

The .mjs is not respected in react-scripts 0.9

https://github.com/facebook/create-react-app/blob/144f03b114f791f66a7db68ae8bc644c8c30a227/packages/react-scripts/config/webpack.config.prod.js#L124-L157

However it was fixed later in some versions between 1.0.0 and 1.0.17:

https://github.com/facebook/create-react-app/blob/4b55193f0ad479f26b0f5e153bb4b152a1ee03e7/packages/react-scripts/config/webpack.config.prod.js#L133-L182

All of the versions mentioned above are 4 years old, when Node.js 6.13 even did not exist. Babel/runtime 7.13 does not support such config, consider upgrade react-scripts to a modern version to correctly handle .mjs.

[fengxinming]

@JLHwung Thank you for your suggestion that is really useful, but I did not use react-scripts in our legacy projects, my last comment means our legacy build tool kind of like react-scripts, there is not a webpack configuration file in the project. I believe the babel team will find a best way to solve it.

[nicolo-ribaudo]

Can you share a repository with a similar setup that shows the bug? It's hard to reproduce it otherwise.

[fengxinming]

I have known the reason that _index.mjs matched the file-loader rule, I just can not directly change the webpack configuration, However thanks to @nicolo-ribaudo and @JLHwung