Salvia 🌿

The Future of Rails View Layer

Salvia is a next-generation Server-Side Rendering (SSR) engine designed to replace ERB with JSX/TSX in Ruby on Rails. It brings the Islands Architecture and True HTML First philosophy to the Rails ecosystem.

Vision: The Road to Sage

Salvia is the core engine for a future framework called Sage (inspired by Express, Hono, and Oak). While Sage will be a complete standalone framework, Salvia is available today as a drop-in replacement for the View layer in Ruby on Rails.

Features

🏝️ Islands Architecture: Render interactive components (Preact/React) only where needed. Zero JS for static content.
🚀 True HTML First: Replace app/views/**/*.erb with app/pages/**/*.tsx.
⚡ JIT Compilation: No build steps during development. Just run rails s.
💎 Rails Native: Seamless integration with Controllers, Routes, and Models.
🦕 Deno Powered: Uses Deno for lightning-fast TypeScript compilation and formatting.

Requirements

Ruby 3.1+
Rails 7.0+ (Recommended)
Deno 1.30+ (Required for JIT compilation and tooling)

Installation

1. Install Deno

Salvia requires Deno. Follow the official installation guide.

# macOS / Linux
$ curl -fsSL https://deno.land/x/install/install.sh | sh

2. Add Gem

Add this line to your Rails application's Gemfile:

gem 'salvia'

And then execute:

$ bundle install

Getting Started

1. Setup Salvia

Run the interactive installer to set up Salvia for your Rails project:

$ bundle exec salvia install

This command will:

Create the salvia/ directory structure.
Generate deno.json (Single Source of Truth for dependencies).
Cache Deno dependencies to ensure fast startup.
Configure Rails to automatically include Salvia::Helpers (providing the ssr method).

Directory Structure

salvia/
├── app/
│   ├── components/  # Shared UI components (Buttons, Cards)
│   ├── islands/     # Interactive components (Hydrated on client)
│   └── pages/       # Server Components (SSR only, 0kb JS to client)
└── deno.json        # Dependency management (Import Map)

2. Create a Page (Server Component)

Delete app/views/home/index.html.erb and create salvia/app/pages/home/Index.tsx:

import { h } from 'preact';

export default function Home({ title }) {
  return (
    <div class="p-10">
      <h1 class="text-3xl font-bold">{title}</h1>
      <p>This is rendered on the server with 0kb JavaScript sent to the client.</p>
    </div>
  );
}

3. Render in Controller

In your Rails controller:

class HomeController < ApplicationController
  def index
    # Renders salvia/app/pages/home/Index.tsx
    render html: ssr("home/Index", title: "Hello Salvia")
  end
end

4. Add Interactivity (Islands)

Create an interactive component in salvia/app/islands/Counter.tsx:

import { h } from 'preact';
import { useState } from 'preact/hooks';

export default function Counter() {
  const [count, setCount] = useState(0);
  return (
    <button onClick={() => setCount(count + 1)} class="btn">
      Count: {count}
    </button>
  );
}

Use it in your Page:

import Counter from '../../islands/Counter.tsx';

export default function Home() {
  return (
    <div>
      <h1>Interactive Island</h1>
      <Counter />
    </div>
  );
}

5. Turbo Drive (Optional)

Salvia works seamlessly with Turbo Drive for SPA-like navigation.

Add Turbo to your layout file (e.g., salvia/app/pages/layouts/Main.tsx):

<head>
  {/* ... */}
  <script type="module">
    import * as Turbo from "@hotwired/turbo";
    Turbo.start();
  </script>
</head>

Since dependencies are managed in deno.json, you don't need to write full URLs.

Core Concepts: Pages vs Islands

Understanding the separation of concerns is crucial for "True HTML First" development.

Feature	Pages (Server Components)	Islands (Client Components)
Path	`salvia/app/pages/`	`salvia/app/islands/`
Environment	Server (Ruby/QuickJS)	Client (Browser)
Interactivity	❌ Static HTML	✅ Interactive (Event Listeners)
State	❌ Stateless	✅ Stateful (Signals/Hooks)
Browser APIs	❌ No (`window`, `document` are mocked)	✅ Yes
Usage	Layouts, Initial Data Fetching	Forms, Modals, Dynamic UI

Documentation

English:
- Wisdom for Salvia: Deep dive into the architecture, directory structure, and "True HTML First" philosophy.
- Reference Guide: Comprehensive guide on usage, API, and configuration.
- Architecture: Internal design of the gem.
Japanese (日本語):
- README: 日本語版README。

Framework Support

Salvia is primarily designed for Ruby on Rails to pave the way for the Sage framework.

Ruby on Rails: First-class support.

Zero Config Architecture

Salvia v0.2.0 adopts a Zero Config philosophy.

deno.json is SSOT: It manages dependencies for both Server (SSR) and Client (Browser).
Auto Import Map: npm: specifiers in deno.json are automatically converted to esm.sh URLs for the browser.
No Build Config: build.ts and sidecar.ts are managed internally, but you can extend globals via salvia.globals in deno.json.

Production & CI

In production environments (e.g., Docker, Heroku, Render):

Deno is required: Ensure Deno is installed in your build/runtime environment.
Build Step: Run bundle exec salvia build during deployment.
- This bundles Islands, generates Import Maps, and builds Tailwind CSS.
- It generates hashed filenames for cache busting.
- Note: While Salvia uses JIT compilation in development for a "No Build" experience, salvia build pre-compiles assets for production to ensure zero runtime compilation overhead.

License

The gem is available as open source under the terms of the MIT License.

salvia_rb

Development

Runtime