webpack.config.js

const babelConfig = require('./babel.config');
const config = require('sapper/config/webpack');
const path = require('path');
const pkg = require('./package.json');
const { preprocess } = require('./svelte.config');
const webpack = require('webpack');

const mode = process.env.NODE_ENV;
const dev = mode !== 'production';

const alias = {
  '@': path.resolve('src'),
  svelte: path.resolve('node_modules', 'svelte'),
};
const extensions = [ '.mjs', '.js', '.json', '.svelte', '.html' ];
const mainFields = [ 'svelte', 'module', 'browser', 'main' ];

module.exports = {
  client: {
    entry: config.client.entry(),
    output: config.client.output(),
    resolve: { alias, extensions, mainFields },
    module: {
      rules: [
        {
          test: /\.(js|svelte)$/,
          exclude: /node_modules\/(?!svelte)/,
          use: {
            loader: 'babel-loader',
            options: babelConfig,
          },
        },
        {
          test: /\.(svelte|html)$/,
          use: {
            loader: 'svelte-loader',
            options: {
              dev,
              hydratable: true,
              hotReload: false, // pending https://github.com/sveltejs/svelte/issues/2377
              preprocess,
            },
          },
        },
      ],
    },
    mode,
    plugins: [
      // pending https://github.com/sveltejs/svelte/issues/2377
      // dev && new webpack.HotModuleReplacementPlugin(),
      new webpack.DefinePlugin({
        'process.browser': true,
        'process.env.NODE_ENV': JSON.stringify(mode)
      }),
    ].filter(Boolean),
    devtool: dev && 'inline-source-map',
  },

  server: {
    entry: config.server.entry(),
    output: config.server.output(),
    target: 'node',
    resolve: { alias, extensions, mainFields },
    externals: Object.keys(pkg.dependencies).concat('encoding'),
    module: {
      rules: [
        {
          test: /\.(js|svelte)$/,
          exclude: /node_modules\/(?!svelte)/,
          use: {
            loader: 'babel-loader',
            options: babelConfig,
          },
        },
        {
          test: /\.(svelte|html)$/,
          use: {
            loader: 'svelte-loader',
            options: {
              css: false,
              generate: 'ssr',
              dev,
              preprocess,
            }
          }
        }
      ]
    },
    mode: process.env.NODE_ENV,
    performance: {
      hints: false // it doesn't matter if server.js is large
    }
  },

  serviceworker: {
    entry: config.serviceworker.entry(),
    output: config.serviceworker.output(),
    mode: process.env.NODE_ENV
  }
};