15.0.0.md

React on Rails 15.0.0 Release Notes

Major Features

🚀 React Server Components Support

Experience the future of React with full RSC integration in your Rails apps:

• Seamlessly use React Server Components
• Reduce client bundle sizes
• Enable powerful new patterns for data fetching
• ⚡️ Requires React on Rails Pro - See the full tutorial

Improved Component Hydration

Major improvements to component and store hydration:

• Components and stores now hydrate immediately rather than waiting for page load
• Enables faster hydration, especially beneficial for streamed pages
• Components can hydrate before the page is fully streamed
• Can use async scripts in the page with no fear of race condition
• No need to use defer anymore

Breaking Changes

Component Hydration Changes

• The defer_generated_component_packs and force_load configurations now default to false and true respectively. This means components will hydrate early without waiting for the full page load. This improves performance by eliminating unnecessary delays in hydration.

  • The previous need for deferring scripts to prevent race conditions has been eliminated due to improved hydration handling. Making scripts not defer is critical to execute the hydration scripts early before the page is fully loaded.
  • The force_load configuration make react-on-rails hydrate components immediately as soon as their server-rendered HTML reaches the client, without waiting for the full page load.
  • If you want to keep the previous behavior, you can set defer_generated_component_packs: true or force_load: false in your config/initializers/react_on_rails.rb file.
  • If we want to keep the original behavior of force_load for only one or more components, you can set force_load: false in the react_component helper or force_load configuration.
  • Redux store support force_load option now and it uses config.force_load value as the default value. Which means that the redux store will hydrate immediately as soon as its server-side data reaches the client. You can override this behavior for individual redux stores by setting force_load: false in the redux_store helper.

• ReactOnRails.reactOnRailsPageLoaded() is now an async function:

  • If you are manually calling this function to ensure components are hydrated (e.g. with async script loading), you must now await the promise it returns:

  // Before
  ReactOnRails.reactOnRailsPageLoaded();
  // Code expecting all components to be hydrated
  
  // After
  await ReactOnRails.reactOnRailsPageLoaded();
  // Code expecting all components to be hydrated

Store Dependencies for Components

When using Redux stores with multiple components, you need to explicitly declare store dependencies to optimize hydration. Here's how:

The Problem

If you have deferred Redux stores and components like this:

<% redux_store("SimpleStore", props: @app_props_server_render, defer: true) %>
<%= react_component('ReduxApp', {}, {prerender: true}) %>
<%= react_component('ComponentWithNoStore', {}, {prerender: true}) %>
<%= redux_store_hydration_data %>

By default, React on Rails assumes components depend on all previously created stores. This means:

• Neither ReduxApp nor ComponentWithNoStore will hydrate until SimpleStore is hydrated
• Since the store is deferred to the end of the page, both components are forced to wait unnecessarily

The Solution

Explicitly declare store dependencies for each component:

<% redux_store("SimpleStore", props: @app_props_server_render, defer: true) %>
<%= react_component('ReduxApp', {}, {
  prerender: true
  <!-- No need to specify store_dependencies - it automatically depends on SimpleStore -->
}) %>
<%= react_component('ComponentWithNoStore', {}, {
  prerender: true,
  store_dependencies: [] <!-- Explicitly declare no store dependencies -->
}) %>
<%= redux_store_hydration_data %>

This allows ComponentWithNoStore to hydrate immediately without waiting for SimpleStore, improving page performance.