Configuration for Babel-Loader Error When Specifying --env

package.json

{
 "scripts": {
    "build:prod": "webpack --env=prod --colors --profile --json > prod.stats.json",
    "build:staging": "webpack --env=dev --colors --profile --json > staging.stats.json",
    "start": "webpack-dev-server --env=dev --open --watch --progress",
  }
}

webpack.config.js

function buildConfig(env) {
  return require(`./config/webpack.${env}.config.js`)(env)
}

module.exports = buildConfig;

webpack.dev.config.js

const path = require("path");
const webpack = require("webpack");

module.exports = function(env) {
  return {
    entry: "./src/app/app.js",
    output: {
      path: path.resolve(__dirname, "staging/js"),
      publicPath: "js/",
      filename: `app.js`,
      sourceMapFilename: `app.map.js`
    },
    module: {
      rules: [
        {
          test: /\.jsx?$/,
          include: [path.resolve(__dirname, "src")],
          exclude: [
            path.resolve(__dirname, "src/js"),
            path.resolve(__dirname, "node_modules")
          ],
          loader: "babel-loader",
          options: {
            presets: ["es2015", "react", "stage-0"],
            plugins: [
              "transform-async-functions",
              "transform-object-rest-spread",
              "transform-regenerator"
            ]
          }
        }
      ]
    },
    devtool: "source-map",
    devServer: {
      contentBase: "staging",
      compress: false,
      port: 9000
    }
  };
};