Cameron Dutro, May 2024 Isomorphic View Components Re-imagining the Rails front-end

Who is this guy? Cameron Dutro GitHub, Inc @camertron@ruby.social github.com/camertron

Who is this guy? ViewComponent maintainer Primer maintainer primer/view_components primer/react primer/css

My journey to GitHub • Sep - Dec 2010: Fluther • 2011 - 2014: Twitter • 2014 - 2020: Lumos Labs • 2020 - 2021: Salesforce (Quip) • 2021 - now: GitHub Rails renaissance

Rails renaissance • Hotwire • Turbo, Turbo Native • RailsWorld announced • ViewComponent was having a moment

ViewComponent A framework for creating reusable, testable & encapsulated view components, built to integrate seamlessly with Ruby on Rails. “ ” viewcomponent.org

ViewComponent example # app/components/greeting_component.rb class GreetingComponent < ViewComponent::Base def initialize(people:) @people = people end end <%# app/components/greeting_component.html.erb %>

Rux # app/components/greeting_component.rux class GreetingComponent < ViewComponent::Base def initialize(people:) @people = people end def call end end Star 385

The story continues • February 2024: I ported GitHub’s global user nav drawer to React • It’s a fantastic experience; React is awesome

The story continues • March 2024: Sin City Ruby conference in Las Vegas • Jason Charnes live-codes an interactive site builder using Rails front-end tooling • Company tried to use Stimulus, Hotwire, Turbo, etc, but ultimately wrote the feature in React • Painful watching Jason switch between so many fi les, connecting things with IDs, etc

ViewComponent interactivity • Render server-side • Use Web Components to attach dynamic behavior • Use github/catalyst to reduce Web Component boilerplate

Web Component example import {controller, target} from '@github/catalyst' @controller class PrimerTextFieldElement extends HTMLElement { @target inputElement: HTMLInputElement @target validationElement: HTMLElement @target validationErrorIcon: HTMLElement toggleValidationStyling(isError: boolean): void { if (isError) { this.validationElement.classList.remove('FormControl-inlineValidation--success') } else { this.validationElement.classList.add('FormControl-inlineValidation--success') } this.validationSuccessIcon.hidden = isError this.validationErrorIcon.hidden = !isError this.inputElement.setAttribute('invalid', isError ? 'true' : 'false') } setError(message: string): void { this.toggleValidationStyling(true) this.setValidationMessage(message) this.validationElement.hidden = false } }

Limitations of Web Components • Imperative, jquery-like code • Find elements, add/remove classes, hide/show, etc • Easy to make a mistake or miss an edge case • Lots of event listener gotchas • Hard to re-render since there’s no template • Di ffi cult to synchronize data model and view layer

React • Mature; large ecosystem • Declarative template, event handlers, refs, etc • Much less error-prone code, easier to reason about • Data binding (updating state updates the view) • Simply magical - no more querySelector().setAttribute() • Template (JSX) lives inside the component

After working in React again, I came to a harsh realization:

React is much, much better than Hotwire, Stimulus, or anything else the Rails front-end has to offer.

No content

React Problems • Dynamism makes it more di ffi cult to write accessible components • No such thing as “static” content • Tends to take over the whole page • Large bundle sizes • Performance concerns on low-end devices • You don’t get to write Ruby

React competitors • Angular • Svelte • Vue • Solid • Qwik • Preact • Next/nuxt

Takeaways • Components are good • Reactivity is good • Declarative is better than imperative

Isomorphic view components What if we could render view components in the browser? “ ” me after Sin City Ruby

My dream class TodoComponent def call end end

My dream class TodoComponent def call end end

My dream class TodoComponent def call end end

My dream class TodoComponent def call end private def save_changes Net::HTTP.post_form(...) end end

View components in the browser • Need a Ruby runtime • Need some way to update the view when state changes • Need a way for Ruby to call JavaScript functions and wrap JavaScript objects

Ruby runtimes • ruby.wasm • MRI Ruby compiled to Web Assembly (WASM) • Large download (~50mb) • Opal.js • Required transpiler step • Sort of a large footprint last time I checked (~400k) + transpiled code

Prior art • Volt • Appears to be unmaintained • Hyperstack • Personally not a fan of the syntax • Built on top of React

Garnet.js • TypeScript implementation of YARV, the Ruby virtual machine • No transpilation - runs Ruby code directly • Smaller footprint (~95k) + Ruby code • Uses the new Prism parser

Garnet.js • Passes the test suites from several gems • Small but capable subset of the Ruby standard library • Decent performance

Neato • Experimental front-end framework for Rails • Uses Rux for templating • Compiles templates to tagged template literals • Uses Garnet to run Ruby code • Uses Lit for rendering and state management

Lit is a simple library for building fast, lightweight web components. At Lit's core is a … base class that provides reactive state, scoped styles, and a declarative template system that's tiny, fast and expressive. “ ” lit.dev/docs

• Lightweight: 5kb • Built on Web Components • Supports isolating CSS styles via browser-native shadow DOM • Uses tagged template literals for templating • “You can build just about any kind of web UI with Lit” - lit.dev

TodoListComponent class TodoListComponent include Neato::Component state :todos def initialize(todos:) @todos = todos end def call {@todos.map do |todo| end} end end

TodoComponent class TodoComponent include Neato::Component state :todo, :errors, :edit refs :name_input, :duration_input def call {if @edit <> {if @errors.include?(:name)

Name {@errors[:name].first}

end} > else @todo[:name] end} … end end

TodoComponent class TodoComponent def call ... {if @edit { save_changes }}> Save else { set_state(edit: true) }}> Edit end} ... end end

TodoComponent class TodoComponent private def save_changes response = Neato.fetch("/todos/#{@todo[:id]}", { method: 'PUT', headers: { "Content-Type": "application/x-www-form-urlencoded" }, body: Neato::URLSearchParams.new( "todo[name]": name_input.value, "todo[duration_mins]": duration_input.value ) }) if response.ok? set_state(todo: response.json[:todo], edit: false, errors: {}) else @todo[:name] = name_input.value @todo[:duration_mins] = duration_input.value set_state( errors: response.json[:errors] ) end end end

Demo time!