Failed to compile - UglifyJs returns undefined

[yormi]

Is this a bug report?

yes

Environment

1. node -v: v10.15.0
2. npm -v: 6.4.1
3. yarn --version (if you use Yarn): 1.12.3
4. npm ls create-elm-app -g (if you haven’t ejected):

Then, specify:

1. Operating system: Arch Linux
2. Browser and version (if relevant): Not relevant

Steps to Reproduce

I import "@babel/polyfill" and then I get:

$ elm-app build
Creating an optimized production build...
Failed to compile.

static/js/vendors~main.ab89a661.chunk.js from UglifyJs
undefined

If I use elm-app start, no problem

If I comment the babel polyfill, it compiles just fine

If I comment the whole Uglify config in the create-elm-app webpack.config.prog.js, it works well.

My guess would be that I should avoid mixing up the babel polyfill with Uglify but I'm not sure how to do that. I used the exclude option (exclude: '@babel/polyfill') of Uglify in webpack.config.prog.js but no success. I guess it's already included in the chunk and therefore processed by the Uglify plugin.

It feels like there's a simple solution but I don't understand the process very well. I'm not even sure why it breaks with ReferenceError: regeneratorRuntime is not defined if I dont use the babel polyfill. From the stack trace it seems to come from customElements.define.

Edit I just saw @babel/plugin-transform-runtime in the webpack config... so why would I get the regeneratorRuntime error then !?

I'll keep investigating but in the meantime, I thought someone could have some useful info to share :)

Let me know what else could be useful !

Thanks for your really helpful work !

Guillaume

[halfzebra]

Hi Guillaume!

We have babel-preset-env already, so maybe it would be helpful to learn about your goals. Is there something specific you want to polyfill?

[yormi]

Hi halfzebra !

Ok so I thought it was related to the Custom Element I use but after looking into it again, I realized that I need the polyfill to use a library that uses ES6.

I thought it was easier to import the babel polyfill than ejecting create-elm-app and change the webpack config to use babel on that library. The problem is that when I run elm-app build, uglify seems to error and cancel the build when it runs on the polyfill.

Any idea if there is a clean solution to use that ES6 library ?

Thanks again !

[Jonsey]

Hi Guillaume,

I'm having exactly the same issue, did you solve the problem?

[yormi]

Hi Jonsey !

No... I didn't find a clean solution =/

I'm looking back at my commits and apparently, I just downgraded the lib to a version that was not depending on ES6...

I'm very keen to hear about your solution if you find one :)

Good luck !

[Jonsey]

I did a clean elm-app create and only added

`test();

const test = async () => {
  console.log("Worked");
}`

this gave me ReferenceError: regeneratorRuntime is not defined when running elm-app build

[Jonsey]

OK, I fixed it, sort of. I'm not sure why the existing set up with @babel/runtime-generator isn't working, but I removed @babel/polyfil from my index.js and added require('regenerator-runtime/runtime');

I know it pollutes the global namespace but I can now compile in debug and production mode

[yormi]

Well done @Jonsey ! That is a way better workaround than downgrading the libs !

And I tip my hat to you @halfzebra for the quick PR :)

[halfzebra]

🎉 This issue has been resolved in version 3.0.6 🎉

The release is available on:

• npm package (@latest dist-tag)
• GitHub release

Your semantic-release bot 📦🚀