Is there a way to preserve license comments?

Question

I'm using babel-loader in my webpack.config.js file but I noticed it removes the license comments of the form:

/*! whatever **/

Is there a way to preserve them? I noticed babel has a commentsoptions, but I guess that would preserve any comment and not just the license ones.

const webpack = require('webpack');

module.exports = {
  resolve: {
    alias: {
      'vue$': 'vue/dist/vue.js'
    }
  },
  module: {
    rules: [
      {
        test: /\.vue$/,
        loader: 'vue-loader',
        options: {
          loaders: {
            scss: 'vue-style-loader!css-loader!sass-loader',
            js: 'babel-loader'
          }
        }
      },
      {
        test: /\.js$/,
        use: {
          loader: 'babel-loader',
        }
      }
    ]
  },
  plugins: [
    new webpack.optimize.UglifyJsPlugin({
      compress: {
        warnings: false,
        drop_console: false,
      }
    })
  ],
};

I already tried:

plugins: [
    new webpack.optimize.UglifyJsPlugin({
      output:{
        comments: true
      }
})

As well as comments: '/^!/' and comments: /^!/. Nothing works.

It only keeps comments if I remove the whole plugins option from the webpack config.

I also tried using license comments such as:

/** comments */

/*! comments */

/*! @license comments */

/*! @preserve comments */

Answer 1

That's a bug, that's been in webpack/uglify since 2015, and never got fixed.

They supposedly fixed it using this by rather adding extractComments to true but still it won't work for some people so a year later in 2019 another PR has been opened to supposedly fixing it.

new UglifyJSPlugin({
  sourceMap: true,
  extractComments: true
})

So it's a known bug that has been hanging around for years. Maybe hacks do exist, but that's the general case.