---
title: How to setup react-rails with esbuild
slug: how-to-setup-react-rails-with-esbuild
published_at: 2023-08-30 19:52:00 +0000
updated_at: 2024-07-27 21:59:30 +0000
summary: In this article, you will learn how to set up `react-rails` with `esbuild` for a seamless integration of React components into a Rails application. 🚀👨‍💻
tags: [Rails, React]
author: CJ Avilla
url: https://www.cjav.dev/articles/how-to-setup-react-rails-with-esbuild
type: article
---

# How to setup react-rails with esbuild

*Published: August 30, 2023*
*Tags: Rails, React*

We need calendars for scheduling home painting projects for some internal tools we're building at [Craftwork](https://craftwork.com).

Before any code was written, the team started with Notion calendars:

![Notion calendaring solution](/rails/active_storage/blobs/eyJfcmFpbHMiOnsiZGF0YSI6MTEsInB1ciI6ImJsb2JfaWQifX0=--d681a9fb4f28b7de55bde4bcd3afb4946db595ed/image.png)

That worked well, but we wanted to integrate calendars into our Rails application deeply. For a while, I've had my eye on the [`simple_calendar`](https://github.com/excid3/simple_calendar) gem. Which works well for setting up basic calendar views! This one uses CSS from the Tailwind UI catalog:

![simple_calendar gem view](/rails/active_storage/blobs/eyJfcmFpbHMiOnsiZGF0YSI6MTIsInB1ciI6ImJsb2JfaWQifX0=--b4680d2901f7033eb347a1826312ab0b029d7a35/image.png)

Again, great for static stuff you want to show on a calendar, but eventually, we wanted to have many multi-day events that can be expanded or contracted to different dates directly on the calendar. A more interactive experience our team has grown to like from the Notion solution.

This was the time to add React into our Rails. That'll be easy, I thought. Just a couple hours of work, I thought. PSSSSSH. Naw, dog -- the gods don't want you putting React in your Rails, for some reason. Or, at least they don't want you to without _their_ build tools!

[Bard](https://bard.google.com/) sent me a marketing email a couple days ago with an example use case of "Comparison" so I asked Bard to compare different libraries for adding React to Rails:

![Bard response](/rails/active_storage/blobs/eyJfcmFpbHMiOnsiZGF0YSI6MTMsInB1ciI6ImJsb2JfaWQifX0=--1b3200a6313984a5cc3f3800d18691927bd5d7e3/image.png)

* `react-rails` (winner?)
* `react_on_rails` (seemingly made from the same people as `react-rails`? Why are these different things? 🤷‍♂️)
* `htm` (naw, the team wants to use jsx)
* `webpacker` (wait, that's not a react thing at all, that's a build tool that I def don't want to use because [I'm allergic to configuration](https://twitter.com/cjav_dev/status/1696958223696167239))

Okay cool, let's dig into [`react-rails`](https://github.com/reactjs/react-rails/).

I scan the README hoping for a few `bundle add` this and `yarn add` that, but we're instead met with two options: `Get started with Shakapacker` or `Use with Asset Pipeline`. We already have a bundler: esbuild, I don't want to switch just to use react. So I try the Asset Pipeline solution first, which didn't work. After trying several things (vite, importmaps, stimulus wrapper), I found a couple of issues on the repo:

https://github.com/reactjs/react-rails/issues/1149

https://github.com/reactjs/react-rails/issues/1134

This dev, [IsmailM](https://github.com/IsmailM), politely asks for documentation for setting up with ESBuild, but the maintainer pushes back and asks why not use webpack with its new support for esbuild. (because... we don't want to touch webpack with a 10-foot pole).

I don't want to use webpack, or webpacker, or shakapacker, or any complex configuration for a simple build process. We only need a small bit of TypeScript to play nicely with React. 

[multiplegeorges](https://github.com/multiplegeorges) commented with a [nice solution](https://github.com/reactjs/react-rails/issues/1149#issuecomment-1001857660) as did [cionescu](https://github.com/cionescu) [here](https://github.com/reactjs/react-rails/issues/1149#issuecomment-1003318505).

multiplegeorges and cionescu's solutions got us close, but didn't work 100%, which is why I'm writing this down:

One of the problems with esbuild is it doesn't come with glob imports out of the box, so we need to add a plugin for that called `esbuild-plugin-import-glob`. We'll also install a bunch of npm packages that `react-rails` tells us to:

```sh
yarn add esbuild-plugin-import-glob
```

And add the plugin:

```js
// esbuild.config.mjs (or .js or whatever)
// other imports
import ImportGlobPlugin from "esbuild-plugin-import-glob";

const config = {
  absWorkingDir: path.join(process.cwd(), "app/javascript"),
  bundle: true,
  entryPoints: entryPoints,
  minify: process.env.RAILS_ENV == "production",
  outdir: path.join(process.cwd(), "app/assets/builds"),
  plugins: [rails(), ImportGlobPlugin.default()],
  sourcemap: process.env.RAILS_ENV != "production"
}
// there's other stuff in here, but just be sure to add ImportGlobPlugin to your plugin array
```

Now you should be able to use import globs in your JavaScript like:

```js
import * as Components from "./components/**/*.{js,ts,jsx,tsx}"
```

Which is exactly what we need to do in our application.js entry point:

```js
// app/javascript/application.js
// other stuff...

import React from "react";
import * as Components from "./components/**/*.{js,ts,tsx,jsx}";

const componentsContext = {}

for (const [_, components] of Object.entries(Components)) {
  components.forEach(({ module }) => {
    Object.entries(module).forEach(([name, component]) => {
      componentsContext[name] = component
    })
  });
}

const ReactRailsUJS = require("react_ujs")

ReactRailsUJS.getConstructor = (name) => componentsContext[name]

ReactRailsUJS.handleEvent('turbo:load', ReactRailsUJS.handleMount, false);
ReactRailsUJS.handleEvent('turbo:frame-load', ReactRailsUJS.handleMount, false);
ReactRailsUJS.handleEvent('turbo:before-render', ReactRailsUJS.handleUnmount, false);
```

Next we'll install the gem and run it's install command:

```sh
bundle add react-rails
rails g react:install
```

The install command creates a bunch of files in the old-school `app/assets/javascripts` directory instead of the 😎 cool new `app/javascript` directory. So I rename the `server_rendering.js` file to move it and then delete the rest:

```sh
mv app/assets/javascripts/server_rendering.js app/javascript/
rm -rf  app/assets/javascripts/
```

While I was debugging, running `node esbuild.config.mjs` a few times helped me debug and get things at least built before starting the server and testing things out.

Next, I created a new `.jsx` file in `app/javascript/components/post.jsx` to test:

```js
import React from 'react';

export const Post = ({ title }) => {
  return (
    <>
      <h1 className="text-2xl font-bold">Hey, <span className="underline">{title}</span></h1>
    </>
  );
}
```

Then, in one of the ERB templates, add this line to render the mount point:

```html
React component: <%= react_component("Post", {title: "It works!"}) %>
```

That spits out a tag with some `data-*` attributes where the component is mounted into:

```html
<div data-react-class="Post" data-react-props="{"title":"It works!"}" data-react-cache-id="Post-0"><h1 class="text-2xl font-bold">Hey, <span class="underline">It works!</span></h1></div>
```

---

Okay, we've got react rendering client side now which is cool. I paired with my boss, the boss, [Mike Bifulco](https://mikebifulco.com/) for a few hours and together, we got [FullCalendar](https://fullcalendar.io/) full sending up in our Rails app with fully working drag and drop and editable events 🔥.

![React rendered FullCalendar](/rails/active_storage/blobs/eyJfcmFpbHMiOnsiZGF0YSI6MTQsInB1ciI6ImJsb2JfaWQifX0=--548a14e7eaa667f1cfcd50fe2e5494f64a405042/image.png)


The next big hurdle is using [`react.email`](https://react.email/) for rendering our email templates. We want to use `react.email` for several reasons. (1) the team has experience with using it to generate nice looking email (2) the generated output supports many email clients nicely (3) we hate writing table HTML and would much rather work with modern dev tool chains.

Once we got react-email rendering client side, I wanted to try getting it working server side. Out of the box, react-email has support for server rendering... if you're using one of their preferred bundlers: shakapacker or the asset pipeline. Otherwise, there's a bit of gymnastics involved.

In the [Server Rendering section of the react-rails readme](https://github.com/reactjs/react-rails/tree/master#server-side-rendering) you'll see that adding `prerender: true` in the third argument to `react_component` should render the component server side. I though, cool, I'll try creating a mailer template that renders a `react_component` built from the `react.email` tools:

```html
<!-- app/views/project_mailer/prep.html.erb -->
<%= react_component("ProjectPrepEmail", { project: @project }, { pretender: true }) %>
```

Theoretically, that should find the `ProjectPrepEmail` component in my component tree and render it's HTML, passing the `project` to the props.

But I was getting this error:

```
Caused by ExecJS::ProgramError: TypeError: Cannot read properties of undefined (reading 'serverRender')
```

Recall that we changed the entry point for application js? The `server_rendering.js` file that comes with `react-rails` wont work with esbuild, so we had to modify it to use our custom glob import thing like this:

```js
// app/javascript/server_rendering.js
import React from "react";
import * as Components from "./components/**/*.{js,ts,tsx,jsx}";

const componentsContext = {}

for (const [_, components] of Object.entries(Components)) {
  components.forEach(({ module }) => {
    Object.entries(module).forEach(([name, component]) => {
      componentsContext[name] = component
    })
  });
}

const ReactRailsUJS = require("react_ujs")

ReactRailsUJS.getConstructor = (name) => componentsContext[name]
```

I left off the event handling stuff because it doesn't matter on the server side, and it doesn't seem to work on the server side either.

Once that's updated, I was able to `yarn build` to get the new `app/assets/builds/server_rendering.js` bundle which is used by react-rails to render server side. 

Check this out!

![Server rendered email component](/rails/active_storage/blobs/eyJfcmFpbHMiOnsiZGF0YSI6MTUsInB1ciI6ImJsb2JfaWQifX0=--c73372fb52b24f41b98f761fa245e1d4633ca000/image.png)

I did also play around with setting up a custom container for working with esbuild, but it doesn't seem like it's required:

```rb
# frozen_string_literal: true
module React
  module ServerRendering
    # Get a compiled file from esbuild's output path
    class EsbuildBundleContainer
      def self.compatible?
        true # Since we're using esbuild for craftwork
      end

      def find_asset(filename)
        asset_path = ::Rails.root.join("app/assets/builds/#{filename}")
        File.read(asset_path)
      end
    end
  end
end

# To render React components in production, precompile the server rendering manifest:
Rails.application.config.assets.precompile += ["server_rendering.js"]
Rails.application.config.react.server_renderer_extensions = ["jsx", "js", "tsx", "ts"]

Rails.application.configure do
  config.react.camelize_props = true # default false

  React::ServerRendering::BundleRenderer.asset_container_class = React::ServerRendering::EsbuildBundleContainer
  config.react.server_renderer = React::ServerRendering::BundleRenderer
end
```


---

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