Saat melakukan update aplikasi untuk menggunakan Ruby on Rails versi 6 dan Webpacker versi 5 dengan React JS, saya mendapatkan error dibawah ini.

Invalid configuration object. Webpack has been initialised using a configuration object that does not match the API schema.
 - configuration.entry should be an non-empty object.
   -> Multiple entry bundles are created. The key is the chunk name. The value can be a string or an array.

Solusinya ternyata sangat mudah, cukup buat berkas app/javascript/packs/application.js karena saat update dari versi Webpacker lama, berkas tersebut tidak otomatis dibuat.

Berikut isi app/javascript/packs/application.js jika sejak awal menggunakan Ruby on Rails 6 dan Webpacker 5.

/* eslint no-console:0 */
// This file is automatically compiled by Webpack, along with any other files
// present in this directory. You're encouraged to place your actual application logic in
// a relevant structure within app/javascript and only use these pack files to reference
// that code so it'll be compiled.
//
// To reference this file, add <%= javascript_pack_tag 'application' %> to the appropriate
// layout file, like app/views/layouts/application.html.erb


// Uncomment to copy all static images under ../images to the output folder and reference
// them with the image_pack_tag helper in views (e.g <%= image_pack_tag 'rails.png' %>)
// or the `imagePath` JavaScript helper below.
//
// const images = require.context('../images', true)
// const imagePath = (name) => images(name, true)

console.log('Hello World from Webpacker')

Jika ingin create file dari terminal dapat menjalankan perintah berikut.

touch app/javascript/packs/application.js