Webpacker 4.2 can't find application in /app/public/packs/manifest.json heroku

Question

I\'m a bit stumped. My local rails app works great with webpacker 4.2 and react, but when deploying to production gives me the wonderful can\'t find application in /ap

Answer 1

If you are using Rails 6+ with webpacker then due to the latest rails 6 update the both javascript and css files are moved under app/javascript instead of app/assets.

app/javascript:
  ├── packs:
  │   # only webpack entry files here
  │   └── application.js
  └── src:
  │   └── application.css
  └── images:
      └── logo.svg

But if you have upgraded from older version to new version but still want to compile CSS from app/assets/stylesheets folder then follow the below tweaks:

1. update the below in config/webpacker.yml for webpack to include app/assets in the resolved path.

// config/webpacker.yml

resolved_paths: ['app/assets']

2. copy below line to app/javascript/packs/application.js.

// app/javascript/packs/application.js

import 'stylesheets/application'

This should fix your CSS compilation issue when you run bin/webpack-dev-server.