v6_upgrade.md

Upgrading from Webpacker 5 to 6

There are several substantial changes in Webpacker 6 that you need to manually account for when coming from Webpacker 5. This guide will help you through it.

Webpacker has become a slimmer wrapper around Webpack

By default, Webpacker 6 is focused on compiling and bundling JavaScript. This pairs with the existing asset pipeline in Rails that's setup to transpile CSS and static images using Sprockets. For most developers, that's the recommended combination. But if you'd like to use Webpacker for CSS and static assets as well, please see integrations for more information.

Webpacker used to configure Webpack indirectly, which lead to a complicated secondary configuration process. This was done in order to provide default configurations for the most popular frameworks, but ended up creating more complexity than it cured. So now Webpacker delegates all configuration directly to Webpack's default configuration setup.

This means you have to configure integration with frameworks yourself, but webpack-merge helps with this. See this example for Vue and scroll to the bottom for more examples.

How to upgrade to Webpacker v6 from v5

1. Consider changing from the v5 default for source_entry_path.

  source_path: app/javascript
  source_entry_path: packs

consider changing to the v6 default:

  source_path: app/javascript
  source_entry_path: /

Then consider moving your app/javascript/packs/* (including application.js) to app/javascript/ and updating the configuration file.

Note, moving your files is optional, as you can stil keep your entries in a separate directory, called something like packs, or entries. This directory is defined within the source_path.

2. Ensure no nested directories in your source_entry_path. Check if you had any entry point files in child directories of your source_entry_path. Files for entry points in child directories are not supported by rails/webpacker v6. Move those files to the top level, adjusting any imports in those files.

The new v6 configuration does not allow nesting, so as to allow placing the entry points at in the root directory of JavaScript. You can find this change here.

3. Rename config/webpack to config/webpack_old

4. Rename config/webpacker.yml to config/webpacker_old.yml

5. Update webpack-dev-server to the current version, greater than 4.2, updating package.json.

6. Upgrade the Webpacker Ruby gem and NPM package

Note: Check the releases page to verify the latest version, and make sure to install identical version numbers of webpacker gem and @rails/webpacker npm package. (Gems use a period and packages use a dot between the main version number and the beta version.)

Example going to a specific version:

# Gemfile
gem 'webpacker', '6.0.0.rc.5'

bundle install

yarn add @rails/webpacker@6.0.0-rc.5 --exact

bundle exec rails webpacker:install

7. Update API usage of the view helpers by changing javascript_packs_with_chunks_tag and stylesheet_packs_with_chunks_tag to javascript_pack_tag and stylesheet_pack_tag. Ensure that your layouts and views will only have at most one call to javascript_pack_tag and at most one call to stylesheet_pack_tag. You can now pass multiple bundles to these view helper methods. If you fail to changes this, you may experience performance issues, and other bugs related to multiple copies of React, like issue 2932. If you expose jquery globally with expose-loader, by using import $ from "expose-loader?exposes=$,jQuery!jquery" in your app/javascript/application.js, pass the option defer: false to your javascript_pack_tag.

8. If you are using any integrations like css, postcss, React or TypeScript. Please see https://github.com/rails/webpacker#integrations section on how they work in v6.

9. Copy over any custom webpack config from config/webpack_old. Common code previously called 'environment' should be changed to 'base', and import environment changed to webpackConfig.

// config/webpack/base.js
const { webpackConfig, merge } = require('@rails/webpacker')
const customConfig = require('./custom')

module.exports = merge(webpackConfig, customConfig)

10. Copy over custom browserlist config from .browserslistrc if it exists into the "browserslist" key in package.json and remove .browserslistrc.

11. Remove babel.config.js if you never changed it. Be sure to have this config in your package.json:

"babel": {
  "presets": [
    "./node_modules/@rails/webpacker/package/babel/preset.js"
  ]
}

See customization example the Customizing Babel Config for React configuration.

12. extensions was removed from the webpacker.yml file. Move custom extensions to your configuration by merging an object like this. For more details, see docs for Webpack Configuration

{
  resolve: {
    extensions: ['.ts', '.tsx', '.vue', '.css']
  }
}

13. Some dependencies were removed in PR 3056. If you see the error: Error: Cannot find module 'babel-plugin-macros', or similar, then you need to yarn add <dependency> where might include: babel-plugin-macros, case-sensitive-paths-webpack-plugin, core-js, regenerator-runtime. Or you might want to remove your dependency on those.

14. If bin/yarn does not exist, create an executable yarn file in your /bin directory.

15. Remove overlapping dependencies from your package.json and rails/webpacker's package.json. For example, don't include webpack directly as that's a dependency of rails/webpacker.

16. Review the new default's changes to webpacker.yml and config/webpack. Consider each suggested change carefully, especially the change to have your source_entry_path be at the top level of your source_path.

17. Make sure that you can run bin/webpacker without errors.

18. Try running RAILS_ENV=production bin/rails assets:precompile. If all goes well, don't forget to clean the generated assets with bin/rails assets:clobber.

19. Run yarn add webpack-dev-server if those are not already in your dev dependencies. Make sure you're using v4+.

20. Try your app!

21. Update any scripts that called /bin/webpack or bin/webpack-dev-server to /bin/webpacker or bin/webpacker-dev-server

Examples of v5 to v6

1. React on Rails Project with HMR and SSR
2. Vue and Sass Example