Webpack 4 chunkhash/contenthash can vary between builds

const path = require('path');
const webpack = require('webpack');
const ProgressBarPlugin = require('progress-bar-webpack-plugin');
const childProcess = require('child_process');
const UglifyJsPlugin = require('uglifyjs-webpack-plugin')
const AssetsPlugin = require('assets-webpack-plugin')
const CleanWebpackPlugin = require('clean-webpack-plugin')
const WebpackBuildNotifierPlugin = require('webpack-build-notifier');

const root = path.resolve(__dirname, './src');
const webappPath = path.resolve(__dirname, '..');
const deployPath = path.resolve(webappPath, './public/assets');

const dev = !process.env.NODE_ENV;
const ci = process.env.NODE_ENV === 'ci';
const prod = process.env.NODE_ENV === 'production';

if (prod) {
  console.log('PRODUCTION MODE ENABLED');
}

// don't hash the filename unless we're building for prod or staging. Hashed filenames interfere with karma tests.
const outputFilename = dev || ci ? '[name].bundle.js' : '[name].[chunkhash].bundle.js';
const excludedMapSources = dev ? [/vendor.*bundle.js/, /manifest.*bundle.js/] : [/manifest.*bundle.js/];

function getPlugins() {
  let plugins = [
    new CleanWebpackPlugin(['public/assets/*'], {
      allowExternal: true,
      root: webappPath
    }),

    new webpack.SourceMapDevToolPlugin({
      filename: "[file].map",
      exclude: excludedMapSources
    }),

    new AssetsPlugin({
      includeManifest: true,
      path: deployPath,
      prettyPrint: true
    })
  ];

  plugins.push(new webpack.NamedModulesPlugin());
  plugins.push(new webpack.optimize.ModuleConcatenationPlugin());

  return plugins;
}

module.exports = {
  context: root,

  mode: prod ? 'production' : 'development',
  devtool: false, // rely on SourceMapDevToolPlugin
  cache: dev,

  stats: {
    chunks: false,
    chunkModules: false,
    entrypoints: false,
    modules: false,
    version: false,
    hash: false,
    timings: false,
  },

  entry: {
    app: './core-app/bootstrap.ts',
    embed: './core-embed/bootstrap.ts'
  },

  watchOptions: {
    aggregateTimeout: 300,
    ignored: /node_modules/
  },

  resolve: {
    extensions: ['.ts', '.tsx', '.js', '.jsx'],
    alias: {
      handsontable: 'handsontable/dist/handsontable.full.js'
    }
  },

  output: {
    filename: outputFilename,
    path: path.resolve(__dirname, '../public/assets'),
  },

  optimization: {
    runtimeChunk: {
      name: "manifest",
    },
    splitChunks: {
      cacheGroups: {
        // default: false,
        commons: {
          test: /[\\/]node_modules[\\/]/,
          name: "vendor",
          chunks: "initial",
          enforce: true
        }
      },
    },
  },

  externals: {
    nvd3: 'window.nv',
    highcharts: "window.Highcharts",
    angular: 'window.angular',
    jquery: 'window.jQuery',
    lodash: 'window._',
    moment: 'window.moment',
    ace: 'window.ace',
    d3: 'window.d3',
    chiliPiper: 'window.ChiliPiper',
  },

  plugins: getPlugins(),

  module: {
    rules: [
      {
        test: /\.ts(x?)$/,
        exclude: [/\.(spec|e2e)\.ts$/],
        use: [{
          loader: 'ts-loader',
          options: {
            experimentalWatchApi: true // seems to work ok atm, but performance improvement varies
          }
        }]
      }, {
        test: /\.(html|css)$/,
        loader: 'raw-loader',
        exclude: /\.async\.(html|css)$/
      }, {
        test: /\.svg$/,
        loader: 'url-loader?' + JSON.stringify({
          name: '[name]_[hash]'
        })
      }
    ]
  }
};