Disclaimer ⚠️

This library is intended for legacy projects—please do not use it on new projects.

Using ERB with JS and CSS files can lead to a fragile setup where your frontend assets are entangled with your backend setup, making it very hard to migrate to different tooling or frameworks.

The goal of this library is to ease out the transition as you gradually remove your .js.erb files.

If you need to share constants or values between the backend and the frontend, a safer and more performant approach is to instead generate JS or TypeScript from Ruby and import it as usual (or viceversa).

Why? 🤔

When migrating to Vite.js from sprockets or similar asset pipelines, it's not unusual to have .erb files that depend on the Ruby runtime to be rendered.

This plugin allows Vite.js to understand .erb files, and render them in the context of your Ruby application.

It provides the same functionality as rails-erb-loader, but for Vite.js.

Installation 💿

Install the package as a development dependency:

npm i -D vite-plugin-erb # yarn add -D vite-plugin-erb

and then add the plugin to your vite.config.ts file:

import { defineConfig } from 'vite'
import Erb from 'vite-plugin-erb'

export default defineConfig({
  plugins: [
    Erb(),
  ],
})

Usage 🚀

Once the plugin is installed, you should be able to start importing .erb files.

// app/frontend/constants.js.erb

export const railsEnv = <%= Rails.env.to_json %>

import { railsEnv } from '~/constants.js.erb'

console.log(`Running in ${railsEnv}`)

Configuration ⚙️

If things are not working out of the box, you might need to tweak some the following settings.

For example:

plugins: [
  Erb({
    engine: 'erb',
    runner: 'ruby ./boot.rb',
    env: { RACK_ENV: process.env.NODE_ENV },
    extendEnv: false,
    timeout: 5000,
  }),
],

engine

The ERB template engine to use. erubi, erubis and erb are supported.

You can manually specify which one to use if needed, but they will be detected automatically.

runner

The command to run the internal ruby script.

If bin/rails is detected, Rails runner will be used, giving you access to the application environment.

You may provide ruby ./boot.rb or something similar if using other frameworks.

env

Additional environment variables to be passed to runner. Defaults to process.env.

extendEnv

Set to false if you want to override process.env instead when providing the env property.

timeout

Te Ruby process will be sent a termination signal if it doesn't return a result under the specified timeout in millis. Defaults to 10000.

A note about spring 🌺

By default DISABLE_SPRING: '1' is set in env because if the spring client is started from Node.js the Ruby renderer process would never finish.

This makes the rendering process significantly slower, specially in large apps.

You may provide env: { DISABLE_SPRING: '0' } to re-enable spring, but make sure to run bin/rails runner '' before starting the Vite dev server to prevent this issue, or reload the page after the first visit (which would timeout).

Acknowledgements

• rails-erb-loader: Provided the foundation for this library. Thanks!

License

This library is available as open source under the terms of the MIT License.