Getting "Cannot convert non-arrow function to a function expression" upon build

• Check if updating to the latest Preact version resolves the issue

Describe the bug I have a helper class which is used within a preact component, and its failing on build due to the mentioned error in the name

To Reproduce This is a class which I am importing to a component to use to help calculate certain stuff:

class DuplicateChecker {
  constructor() {
    this.iframe = this.createIframe();
  }

  hasDuplicates = async () => {
    const check = await this.isDuplicateFoundOnFirst();

    return check;
  }

isDuplicateFoundOnFirst = () => {
    // do some stuff here
  }

createIframe = () => {
 // do something here
}
}

export const duplicateChecker = new DuplicateChecker();

and this is the error i am receiving upon building the application as it runs on dev without any problems:

 Cannot convert non-arrow function to a function expression.
  14 |   }
  15 |
> 16 |   hasDuplicates = async () => {
     |                      ^
  17 |     const checkFirstPage = await this.isDuplicateFoundOnFirst();
  18 |

Expected behavior The app builds and compiles any code using babel without any issues.

[rschristian]

So I ran into this StackOverflow question which seems to match your question here, and I see you’ve provided your .babelrc.

I’m not entirely sure that the .babelrc pickup is working as intentioned at the moment, even a plain { "presets": ["preact-cli/babel"] } runs into this issue. AFAIK that should be fine, will need to look into that more.

Regardless, you’re adding a couple redundant plugins and you can add the ones you actually need through your preact config file:

preact.config.js

export default (config, env, helpers) => {
    const { rule } = helpers.getLoadersByName(config, 'babel')[0];
    const babelConfig = rule.options;

    babelConfig.plugins.push(
        '@quickbaseoss/babel-plugin-styled-components-css-namespace',
        'babel-plugin-styled-components'
    );
}

[devlukasz]

This seems to be working! Deleted my .babelrc and used @rschristian way of adding babel plugisn and it seems to be running fine, so there is an issue with .babelrc most likely @developit