next.config.js

'use strict'

const envFlag = require('node-env-flag')
const webpack = require('webpack')
const shouldAnalyze = envFlag(process.env.ANALYZE)
const assetPrefix = process.env.NEXT_ASSET_PREFIX

module.exports = {
  webpack: config => {
    config.plugins.push(
      new webpack.EnvironmentPlugin({ BASE_URL: null, LONG_CACHE: null })
    )

    if (shouldAnalyze) {
      // We don't include webpack-bundle-analyzer in devDependencies, so  load
      // lazily.
      const { BundleAnalyzerPlugin } = require('webpack-bundle-analyzer')
      config.plugins.push(
        new BundleAnalyzerPlugin({
          analyzerMode: 'server',
          analyzerPort: 8888,
          openAnalyzer: true,
        })
      )
    }

    config.module.rules.push({
      test: /\.yml$/,
      use: {
        loader: 'js-yaml-loader',
      },
    })

    if (assetPrefix) {
      config.output.publicPath = `${assetPrefix}/${config.output.publicPath}`
    }

    return config
  },
  exportPathMap: () => ({
    '/': { page: '/' },
  }),
}

// Avoid setting an `undefined` value. This causes
// `TypeError: Cannot read property 'replace' of undefined` at build time.
if (assetPrefix) {
  module.exports.assetPrefix = assetPrefix
}