Webpack process never exits on missing JS import

[lneveu]

• Operating System: Debian 8 (jessie)
• Node Version: 10.15.3
• NPM Version: 6.9.0
• webpack Version: 4.39.2
• sass-loader Version: 8.0.0

Expected Behavior

In bail mode, Webpack build process should fail out and stop on first error (in this case, a missing import file).

Actual Behavior

Webpack build process get stuck after throwing the expected error. The process never exits.

Code

// webpack.config.js
const path = require('path');
module.exports = {
  mode: 'production',
  bail: true,
  entry: {
    app: ['./src/app.js', './src/foo.scss']
  },
  output: {
    path: path.resolve(__dirname, './dist')
  },
  module: {
    rules: [
      {
        test: /\.js$/,
        use: 'babel-loader'
      },
      {
        test: /.s?css$/,
        use: ['css-loader', 'sass-loader']
      }
    ]
  }
};

// src/app.js
import './missing-module'; // <-- this import will fail on purpose
console.log('app');

// src/foo.scss
@import './bar';
body { color: red; }

// src/bar.scss
h1 { color: blue; }

How Do We Reproduce?

Run Webpack using the given configuration.
Mandatory conditions to reproduce the bug:

• bail mode must be enabled
• a scss file must be specified in the entry list
• the scss entry point (foo.scss, here) must contains a valid @import. If foo.scss is replaced by bar.scss, everything works as expected.

Let me know if you need more details.
Thanks!

[alexander-akait]

Please create minimum reproducible test repo

[alexander-akait]

Can't reproduce

[lneveu]

Sure: https://github.com/lneveu/bug-repro-webpack-sass-loader
Just run webpack inside the repo.

[alexander-akait]

Thanks look on this in near future

[lneveu]

I found similar issues here: nodejs/node#17872 and here: #523.

A fix was proposed and merged in the main Webpack repository: webpack/webpack#6193. I tried to apply the same patch, but in webpack/cli (since the code was moved there: https://github.com/webpack/webpack-cli/blob/master/bin/cli.js#L317) and it seems to fix the bug.
I'll submit a pull request in the cli repo.

[alexander-akait]

let's close in favor webpack/webpack-cli#1078, anyway thanks for the issue and the PR