Expose the `mode` option for loaders

Do you want to request a feature or report a bug? A feature.

What is the current behavior? Currently, loaders don’t have access to webpack’s mode option.

What is the expected behavior? Loaders should have access to mode.

If this is a feature request, what is motivation or use case for changing the behavior? Does it make sense to expose the mode option to loaders? Loaders might use it to apply mode-specific optimizations – e.g., css-loader could enable minification in the production mode automatically.

This decreases the number of things a user has to know about and configure to make things work right.

(If the option is already exposed – sorry, just point me to it, I haven’t found it.)

[alexander-akait]

Feel free to send a PR to expose the mode option for loaders

[terminalqo]

webpack.common.js:

const devMode = process.env.NODE_ENV !== 'production';    //devMode = undefined
 module.exports = {
    module: {
        rules: [
         {
           test: /\.css$/,
           use: [
             devMode ? 'style-loader' : MiniCssExtractPlugin.loader,
             'css-loader'
            ]
          }
        ]
    }
  },

webpack.prod.js:

module.exports = merge(common, {
   mode: 'production'
})

package.json:

 "build": "webpack --config webpack.prod.js",  // not work
// "build": "webpack --mode=production --config webpack.prod.js", // not work
// "build": "cross-env NODE_ENV=production webpack --config webpack.prod.js", // work