Can't import .mjs modules in the main process

Describe the bug Some libraries include Ecmascript Modules as .mjs files, it is impossible to import them.

./node_modules/node-fetch/lib/index.mjs 496:11-22
Can\'t import the named export \'PassThrough\' from non EcmaScript module (only default export is available) at HarmonyImportSpecifierDependency._getErrors 
(/Users/totominc/Desktop/Git/poe-mapper-assistant/node_modules/webpack/lib/dependencies/HarmonyImportSpecifierDependency.js:90:6)
at HarmonyImportSpecifierDependency.getErrors (/Users/totominc/Desktop/Git/poe-mapper-assistant/node_modules/webpack/lib/dependencies/HarmonyImportSpecifierDependency.js:68:16)
at Compilation.reportDependencyErrorsAndWarnings (/Users/totominc/Desktop/Git/poe-mapper-assistant/node_modules/webpack/lib/Compilation.js:1334:22)
at Compilation.finish (/Users/totominc/Desktop/Git/poe-mapper-assistant/node_modules/webpack/lib/Compilation.js:1136:9)
at hooks.make.callAsync.err (/Users/totominc/Desktop/Git/poe-mapper-assistant/node_modules/webpack/lib/Compiler.js:545:17)
at _err0 (eval at create (/Users/totominc/Desktop/Git/poe-mapper-assistant/node_modules/tapable/lib/HookCodeFactory.js:24:12), <anonymous>:11:1)
at _addModuleChain (/Users/totominc/Desktop/Git/poe-mapper-assistant/node_modules/webpack/lib/Compilation.js:1064:12)
at processModuleDependencies.err (/Users/totominc/Desktop/Git/poe-mapper-assistant/node_modules/webpack/lib/Compilation.js:980:9)
at process._tickCallback (internal/process/next_tick.js:61:11)
@ ./src/background.ts\n @ multi ./src/background.ts

To Reproduce

1. yarn add node-fetch && yarn add @types/node-fetch -D

import fetch from 'node-fetch';

fetch('https://google.fr')
	.then(response => console.log(response))
	.then(body => console.log(body));

1. yarn serve:electron

Expected behavior It should import node-fetch successfully, same for all .ejs modules.

Environment (please complete the following information):

• OS and version: Mac OS X 10.13.6
• Node version: 10.8.0
• npm version: 6.2.0
• yarn version (if used): 1.9.4
• vue-cli-plugin-electron-builder version: latest
• other vue plugins used: typescript
• custom config for vcp-electron-builder: none
• (if possible) link to your repo: repo private, sorry

[TotomInc]

The issue seems to be a lot more complex and not anymore related to .mjs modules, setting the following config is working fine:

// vue.config.js
module.exports = {
  pluginOptions: {
    electronBuilder: {
      builderOptions: {
        chainWebpackMainProcess: (config) => {
          config.module.rule('javascript/auto').test(/\.mjs$/);
        },
      }
    }
  }
}

The issue I have now is kinda related to node-fetch or webpack, it is exactly the same problem as here.

I’m closing the issue since .mjs files are successfully imported, and I will look to use another HTTP fetch module.

[nklayman]

No, I set the externals manually. It is much faster to bundle with webpack so I only externalize native deps. I can’t always check if a dep is native so you may have to list it manually.