Upgrading React on Rails

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If you would like help in migrating between React on Rails versions or help with implementing server rendering, please contact [email protected] for information about our ShakaCode Pro Support.

We specialize in helping companies to quickly and efficiently move from versions before 9 to current. The older versions use the Rails asset pipeline to package client assets. The current and recommended way is to use Webpack 4 for asset preparation. You may also need help migrating from the rails/webpacker's Webpack configuration to a better setup ready for Server Side Rendering.

Upgrading rails/webpacker from v3 to v4

Custom Webpack build file

The default value for extract_css is false in config/webpack.yml. Custom webpack builds should set this value to true or else no CSS link tags are generated. You have a custom webpack build if you are not using [rails/webpacker](https://github.com/rails/webpacker to setup your Webpack configuration.

  default: &default
     # other stuff
     extract_css: true
     # by default, extract and emit a css file. The default is false

Upgrading to version 11

  • Remove server_render_method from config/initializers/react_on_rails.rb. Alternate server rendering methods are part of React on Rails Pro. If you want to use a custom renderer, contact [email protected] We have a custom node rendering solution in production for egghead.io.
  • Remove your usage of ENV["TRACE_REACT_ON_RAILS"] usage. You can get all tracing with either specifying trace at your component or in your config/initializers/react_on_rails.rb file.
  • ReactOnRails::Utils.server_bundle_file_name and ReactOnRails::Utils.bundle_file_name were removed. React on Rails Pro contains upgrades to enable component and other types caching with React on Rails.

Upgrading to version 10

Pretty simple:

  • Follow the steps to migrate to version 9 (except installing 10.x instead of 9.x)
  • If you have react_component returning hashes, then switch to react_component_hash instead

Upgrading to version 9

Why Webpacker?

Webpacker provides areas of value:

  • View helpers that support bypassing the asset pipeline, which allows you to avoid double minification and enable source maps in production. This is 100% a best practice as source maps in production greatly increases the value of services such as HoneyBadger or Sentry.
  • A default Webpack config so that you only need to do minimal modifications and customizations. However, if you're doing server rendering, you may not want to give up control. Since Webpacker's default webpack config is changing often, we at Shakacode can give you definitive advice on webpack configuration best practices. In general, if you're happy with doing your own Webpack configuration, then we suggest using the client strategy discussed below. Most corporate projects will prefer having more control than direct dependence on webpacker easily allows.

Integrating Webpacker

Reason for doing this: This enables your webpack bundles to bypass the Rails asset pipeline and it's extra minification, enabling you to use source-maps in production, while still maintaining total control over everything in the client directory

From version 7 or lower

...while keeping your client directory
  • .gitignore: add /public/webpack/*
  • Gemfile: bump react_on_rails and add webpacker
  • layout views: anything bundled by webpack will need to be requested by a javascript_pack_tag or stylesheet_pack_tag.
    • Search your codebase for javascript_include_tag. Use the
  • config/initializers/assets.rb: we no longer need to modify Rails.application.config.assets.paths or append anything to Rails.application.config.assets.precompile.
  • config/initializers/react_on_rails.rb:
    • Delete config.generated_assets_dir. Webpacker's config now supplies this information
    • Replace config.npm_build_(test|production)_command with config.build_(test|production)_command
  • config/webpacker.yml: start with our example config (feel free to modify it as needed). I recommend setting dev_server.hmr to false however since HMR is currently broken.
  • client/package.json: bump react_on_rails (I recommend bumping webpack as well). You'll also need js-yaml if you're not already using eslint and webpack-manifest-plugin regardless.
Client Webpack config:
  • You'll need the following code to read data from the webpacker config:
const path = require('path');
const ManifestPlugin = require('webpack-manifest-plugin'); // we'll use this later

const webpackConfigLoader = require('react-on-rails/webpackConfigLoader');
const configPath = path.resolve('..', 'config');
const { output } = webpackConfigLoader(configPath);
  • That output variable will be used for webpack's output rules:
  output: {
    filename: '[name]-[chunkhash].js', // [chunkhash] because we've got to do our own cache-busting now
    path: output.path,
    publicPath: output.publicPath,
  • ...as well as for the output of plugins like webpack-manifest-plugin:

      new ManifestPlugin({
        publicPath: output.publicPath,
        writeToFileEmit: true
  • If you're using referencing files or images with url-loader & file-loader, their publicpaths will have to change as well: publicPath: '/webpack/',
  • If you're using css-loader, webpack.optimize.CommonsChunkPlugin, or extract-text-webpack-plugin, they will also need cache-busting!

...and you're finally done!

...while replacing your client directory
  • Make the same changes to config/initializers/react_on_rails.rb as described above
  • Upgrade RoR & add Webpacker in the Gemfile
  • Upgrade RoR in the client/package.json
  • Run bundle
  • Run rails webpacker:install
  • Run rails webpacker:install:react
  • Run rails g react_on_rails:install
  • Move your entry point files to app/javascript/packs
  • Either:
    • Move all your source code to app/javascript/bundles, move your linter configs to the root directory, and then delete the client directory
    • or just delete the webpack config and remove webpack, its loaders, and plugins from your client/package.json.

...and you're done.

From version 8

For an example of upgrading, see react-webpack-rails-tutorial/pull/416.

  • Breaking Configuration Changes

    1. Added config.node_modules_location which defaults to "" if Webpacker is installed. You may want to set this to 'client'toconfig/initializers/react_on_rails.rbto keep your node_modules inside of/client`
    2. Renamed
      • config.npm_build_test_command ==> config.build_test_command
      • config.npm_build_production_command ==> config.build_production_command
  • Update the gemfile. Switch over to using the webpacker gem.

gem "webpacker"
  • Update for the renaming in the WebpackConfigLoader in your webpack configuration. You will need to rename the following object properties:

    • webpackOutputPath ==> output.path
    • webpackPublicOutputDir ==> output.publicPath
    • hotReloadingUrl ==> output.publicPathWithHost
    • hotReloadingHostname ==> settings.dev_server.host
    • hotReloadingPort ==> settings.dev_server.port
    • hmr ==> settings.dev_server.hmr
    • manifest ==> Remove this one. We use the default for Webpack of manifest.json
    • env ==> Use const { env } = require('process');
    • devBuild ==> Use const devBuild = process.env.NODE_ENV !== 'production';
  • Edit your Webpack.config files:

    • Change your Webpack output to be like this. Be sure to have the hash or chunkhash in the filename, unless the bundle is server side.:

      const webpackConfigLoader = require('react-on-rails/webpackConfigLoader');
      const configPath = resolve('..', 'config');
      const { output, settings } = webpackConfigLoader(configPath);
      const hmr = settings.dev_server.hmr;
      const devBuild = process.env.NODE_ENV !== 'production';
      output: {
        filename: isHMR ? '[name]-[hash].js' : '[name]-[chunkhash].js',
        chunkFilename: '[name]-[chunkhash].chunk.js',
        publicPath: output.publicPath,
        path: output.path,
    • Change your ManifestPlugin definition to something like the following

      new ManifestPlugin({
          publicPath: output.publicPath,
          writeToFileEmit: true
  • Find your webpacker_lite.yml and rename it to webpacker.yml

    • Consider copying a default webpacker.yml setup such as https://github.com/shakacode/react-on-rails-v9-rc-generator/blob/master/config/webpacker.yml
    • If you are not using the webpacker webpacker setup, be sure to put in compile: false in the default section.
    • Alternately, if you are updating from webpacker_lite, you can manually change these:
    • Add a default setting
      cache_manifest: false
    • For production, set:
      cache_manifest: true
    • Add a section like this under your development env:
        host: localhost
        port: 3035
        hmr: false
      Set hmr to your preference.
    • See the example spec/dummy/config/webpacker.yml.
    • Remove keys hot_reloading_host and hot_reloading_enabled_by_default. These are replaced by the dev_server key.
    • Rename webpack_public_output_dir to public_output_path.
  • Edit your Procfile.dev

    • Remove the env value WEBPACKER_DEV_SERVER as it's not used
    • For hot loading:
      • Set the hmr key in your webpacker.yml to true.

Without integrating webpacker

  • Bump your ReactOnRails versions in Gemfile & package.json
  • In /config/initializers/react_on_rails.rb:
    • Rename config.npm_build_test_command ==> config.build_test_command
    • Rename config.npm_build_production_command ==> config.build_production_command
    • Add config.node_modules_location = "client"

...and you're done.

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