razzle.config.js

'use strict';

const path = require('path');
const fs = require('fs');
const appDirectory = fs.realpathSync(process.cwd());
const resolveApp = relativePath => path.resolve(appDirectory, relativePath);

module.exports = {
  modify: (defaultConfig, { target, dev }, webpack) => {
    const config = Object.assign({}, defaultConfig);

    config.module.rules = config.module.rules.reduce((rules, rule) => {

      if (rule.test &&
        rule.test.toString()===/\.(js|jsx|mjs)$/.toString() &&
        !rule.enforce) {

        const { include, ...rest } = rule;

        rules.push({ ...rest, ...{
          include: include.concat([resolveApp('api')])
        }});

      }
      else {
        rules.push(rule);
      }
      
    return rules;
    
  }, []);
  
  return config;
  
};