Ember CLI Rails

Unify your EmberCLI and Rails Workflows!

EmberCLI-Rails is designed to give you the best of both worlds:

• Stay up to date with the latest JavaScript technology and EmberCLI addons
• Develop your Rails API and Ember front-ends from within a single process
• Inject Rails-generated content into your EmberCLI application
• Avoid Cross-Origin Resource Sharing gotchas by serving your EmberCLI applications and your API from a single domain
• Write truly end-to-end integration tests, exercising your application's entire stack through JavaScript-enabled Capybara tests
• Deploy your entire suite of applications to Heroku with a single git push

If you're having trouble, checkout the example project!

EmberCLI-Rails Supports EmberCLI 1.13.13 and later.

Install

Add the following to your Gemfile:

gem "ember-cli-rails"

Then run bundle install:

$ bundle install

If you haven't created an Ember application yet, generate a new one:

$ ember new frontend --skip-git

Setup

First, generate the gem's initializer:

$ rails generate ember:init

This will create the following initializer:

# config/initializers/ember.rb

EmberCli.configure do |c|
  c.app :frontend
end

This initializer assumes that your Ember application exists in Rails.root.join("frontend").

If this is not the case, you could

• move your existing Ember application into Rails.root.join("frontend")
• configure frontend to reference the Ember application in its current directory:

c.app :frontend, path: "~/projects/my-ember-app"

Initializer options

• name - this represents the name of the Ember CLI application.

• path - the path where your Ember CLI application is located. The default value is the name of your app in the Rails root.

• silent - quiets the build. A classic application is built with ember build --silent; a Vite-based one with vite build --logLevel error, which keeps errors while dropping the progress output.

• package_manager - the package manager that installs the application's NodeJS dependencies: :npm (the default), :yarn, or :pnpm. Name the executable with npm_path, yarn_path, or pnpm_path when it is not on the $PATH.

• dev_server - configures Vite's development server for Vite-based applications in development. Pass false to opt out of it, or a Hash of host, port, and timeout settings.

EmberCli.configure do |c|
  c.app :adminpanel # path defaults to `Rails.root.join("adminpanel")`
  c.app :frontend,
    path: "/path/to/your/ember-cli-app/on/disk"
  c.app :payments, silent: true # by default it's false
end

Next, if your Ember application uses the classic (Broccoli-based) build (generated with ember-cli < 6.8), install the ember-cli-rails-addon:

$ cd path/to/frontend
$ ember install ember-cli-rails-addon

Be sure that the addon's MAJOR and MINOR version matches the gem's MAJOR and MINOR versions.

For instance, if you're using the 0.6.x version of the gem, specify ~> 0.6.0 in your Ember app's package.json:

{
  "devDependencies": {
    "ember-cli-rails-addon": "~> 0.6.0"
  }
}

If your Ember application uses the Vite-based build (generated with ember-cli >= 6.8), do not install the addon: it is incompatible with the Vite-based build, and ember-cli-rails does not require it there.

Mount

Configure Rails to route requests to the frontend Ember application:

# config/routes.rb

Rails.application.routes.draw do
  mount_ember_app :frontend, to: "/"
end

Routing options

• to - The path to handle as an Ember application. This will only apply to format: :html requests. Additionally, this will handle child routes as well. For instance, mounting mount_ember_app :frontend, to: "/frontend" will handle a format: :html request to /frontend/posts. Note: If you specify a custom path, you must also update the rootURL in frontend/config/environment.js. See Mounting multiple Ember applications for more information. Note: Requests without Accept: text/html — curl's default, most health checkers — skip this route and receive the raw index.html from the asset handler.
• controller - Defaults to "ember_cli/ember"
• action - Defaults to "index"

Finally, install your Ember application's dependencies:

$ rake ember:install

Boot your Rails application, navigate to "/", and view your EmberCLI application!

Develop

EmberCLI Rails exposes several useful rake tasks.

ember:install

Install the Ember applications' dependencies.

ember:compile

Compile the Ember applications.

ember:test

Execute Ember's test suite.

If you're using Rake to run the test suite, make sure to configure your test task to depend on ember:test.

For example, to configure a bare rake command to run both RSpec and Ember test suites, configure the default task to depend on both spec and ember:test.

task default: [:spec, "ember:test"]

Vite-based applications

When Rails is running in development mode, classic (Broccoli-based) Ember applications are built with ember build --watch, so changes to the Ember application are picked up automatically.

Vite-based Ember applications (generated with ember-cli >= 6.8) are served by Vite's own development server instead — the same one the application's npm start script runs. ember-cli-rails starts it on the first request, waits for it to accept connections, and shuts it down when Rails exits.

Rails still renders the application's index.html, but reads it from the development server rather than from disk. The root-relative URLs in that document are rewritten to point at the development server, so the browser loads the application's modules — and Vite's HMR client — from it directly. The rewriting covers every tag the server emits: Vite externalizes even the document's inline bootstrapping script. Changes to the Ember application are hot-reloaded without reloading the page, and without restarting Rails.

Assets that the Ember application references relatively (an <img> in a template, for instance) are still requested from Rails, which proxies them to the development server.

Configuring the development server

By default the development server listens on an available port on 127.0.0.1, and ember-cli-rails waits up to 30 seconds for it to start:

EmberCli.configure do |c|
  c.app :frontend, dev_server: { host: "127.0.0.1", port: 4200, timeout: 60 }
end

If something is already listening on the configured host and port, ember-cli-rails uses it instead of starting a second server. That makes it possible to run npm start yourself, on a port the initializer names, and have Rails serve the application from it.

host is both the address the development server binds to and — together with port — the origin the browser loads the application's modules from. When the two differ, configure the browser-facing origin separately with origin. The typical case is Rails running in a container: the development server must bind to 0.0.0.0 to be reachable through the container's published port, but browsers refuse to connect to http://0.0.0.0:

EmberCli.configure do |c|
  c.app :frontend, dev_server: {
    host: "0.0.0.0",
    port: 4200,
    origin: "http://localhost:4200",
  }
end

With host: "0.0.0.0", Rails itself reaches the development server through the loopback interface.

Vite's default CORS setting allows localhost origins only: to open the page on a LAN IP or a custom domain, configure server.cors in vite.config.*.

The development server's output is written to log/ember-<app>.<environment>.log.

Opting out

To build the application once, synchronously, on the first request instead of running a development server, disable it:

EmberCli.configure do |c|
  c.app :frontend, dev_server: false
end

Changes to the Ember application are then only picked up by restarting the Rails server.

The development server is only used in development. test and production are served from the output of ember build, as they always have been.

Deploy

When Rails is running in production mode, EmberCLI-Rails stops doing runtime compilation. Instead, configured apps are built during rake assets:precompile. This keeps things quick for end users, and extends the normal Rails asset building process.

Configuration information, including instructions for Heroku and Capistrano, can be found below.

CDN

In production environments, assets should be served over a Content Delivery Network.

Configuring an ember-cli-rails application to serve Ember's assets over a CDN is very similar to configuring an EmberCLI application to serve assets over a CDN:

var app = new EmberApp({
  fingerprint: {
    prepend: 'https://cdn.example.com/'
  }
});

If you're serving the Ember application from a path other than "/", the prepend URL must end with the mounted path:

var app = new EmberApp({
  fingerprint: {
    // for an Ember application mounted to `/admin_panel/`
    prepend: 'https://cdn.example.com/admin_panel/',
  }
});

As long as your CDN is configured to pull from your Rails application , your assets will be served over the CDN.

Deployment Strategies

By default, EmberCLI-Rails uses a file-based deployment strategy that depends on the output of ember build.

Using this deployment strategy, Rails will serve the index.html file and other assets that ember build produces.

These EmberCLI-generated assets are served with the same Cache-Control headers as Rails' other static files:

# config/environments/production.rb
Rails.application.configure do
  # serve static files with cache headers set to expire in 1 year
  config.static_cache_control = "public, max-age=31622400"
end

If you need to override this behavior (for instance, if you're using ember-cli-deploy's "Lightning Fast Deployment" strategy in production), you can specify the strategy's class in the initializer:

EmberCli.configure do |config|
  config.app :frontend, deploy: { production: EmberCli::Deploy::Redis }
end

This example configures the frontend Ember application to retrieve the index's HTML from an ember-cli-deploy-redis -populated Redis entry using the ember-cli-rails-deploy-redis gem.

If you're deploying HTML with a custom strategy in development or test, disable EmberCLI-Rails' build step by setting ENV["SKIP_EMBER"] = true.

NOTE:

Specifying a deployment strategy is only supported for applications that use the mount_ember_app and render_ember_app helpers.

Heroku

To configure your EmberCLI-Rails applications for Heroku:

1. Execute rails generate ember:heroku.
2. Commit the newly generated files.
3. Add the NodeJS buildpack.

$ heroku buildpacks:clear
$ heroku buildpacks:add --index 1 heroku/nodejs
$ heroku buildpacks:add --index 2 heroku/ruby
$ heroku config:unset SKIP_EMBER

You are ready to deploy:

$ git push heroku master

EmberCLI compilation happens at deploy-time, triggered by the assets:precompile rake task. This is the same for both build systems: Vite's development server only runs in development, so a Vite-based application deploys exactly like a classic one — ember build writes to the build directory, and Rails serves the result.

NOTE Run the generator each time you introduce additional EmberCLI applications into the project.

Package manager — the buildpack installs the package manager the project root's lockfile names. The generator writes an empty yarn.lock or pnpm-lock.yaml when an application is configured with yarn or pnpm as its package_manager, and copies the packageManager field the Ember applications declare into the generated package.json so that the buildpack installs that version. Without a packageManager field the buildpack installs the latest pnpm release.

NodeJS version — the buildpack reads engines.node from the project root's package.json (the file the generator writes), not from the Ember application's, and builds on the current LTS release when it names no version. Make sure the generated file requires a NodeJS that satisfies your Ember application's own engines.node: applications generated with ember-cli >= 6.8 require NodeJS >= 20.19.0.

Slug size

Heroku slug size is limited. The build process creates artifacts that are not necessary for the server to run, but are included in the deployed Heroku slug.

Omitting these build assets can dramatically reduce slug size.

A build-pack solution for this is discussed in Issue #491.

Capistrano

EmberCLI-Rails installs the Ember application's NodeJS dependencies during EmberCLI's compilation, triggered by the assets:precompile rake task. It runs npm install, yarn install, or pnpm install, as the application's package_manager option names.

The executables it runs are required to be defined in the deployment SSH session's $PATH. It is not sufficient to modify the session's $PATH in a .bash_profile.

To resolve this issue, prepend the Node installation's bin directory to the target system's $PATH:

#config/deploy/production.rb

set :default_env, {
  "PATH" => "/home/deploy/.nvm/versions/node/v22.11.0/bin:$PATH"
}

The system in this example is using nvm to configure the node version. If you're not using nvm, make sure the string you prepend to the $PATH variable contains the directory or directories that contain the executables above. Point it at a NodeJS that satisfies the Ember application's engines.node: applications generated with ember-cli >= 6.8 require NodeJS >= 20.19.0.

For faster deployments

Place the following in your deploy/<environment>.rb

set :linked_dirs, %w{<ember-app-name>/node_modules}

to avoid rebuilding all the node modules with every deploy. Replace <ember-app-name> with the name of your ember app (default is frontend).

Override

By default, routes defined by ember_app will be rendered with the internal EmberCli::EmberController.

Overriding the view

The EmberCli::EmberController renders the Ember application's index.html and injects the Rails-generated CSRF tags into the <head>.

To customize the view, create app/views/ember_cli/ember/index.html.erb:

<%= render_ember_app ember_app do |head| %>
  <% head.append do %>
    <%= csrf_meta_tags %>
  <% end %>
<% end %>

The ember_app helper is available within the EmberCli::EmberController's view, and refers to the name of the current EmberCLI application.

To inject the EmberCLI generated index.html, use the render_ember_app helper in your view:

<!-- app/views/application/index.html.erb -->
<%= render_ember_app :frontend do |head, body| %>
  <% head.append do %>
    <%= csrf_meta_tags %>
  <% end %>

  <% body.append do %>
    <%= render partial: "my-analytics" %>
  <% end %>
<% end %>

The body block argument and the corresponding call to body.append in the example are both optional, and can be omitted.

render_ember_app emits a complete HTML document, so render it with the layout disabled (see below).

Serving Rails-generated CSS

For more information on how to work with EmberCLI-generated stylesheets, refer to the Stylesheets section. EmberCLI-generated CSS will be embedded in the response's HTML document by default.

To serve assets generated and served by Rails, inject them into the document's <head>:

<%= render_ember_app :frontend do |head| %>
  <% head.append do %>
    <%= stylesheet_link_tag "application" %>
    <%= csrf_meta_tags %>
  <% end %>
<% end %>

There are no technical limitations to sharing assets between the Ember client and the Rails server, but picking one or the other might simplify the project's organization.

Sharing code during asset compilation is not possible.

For example, Ember's SCSS files cannot use @import directives referencing Rails' SCSS modules.

Overriding the controller

To override this behavior, you can specify [any of Rails' routing options] route-options.

For the sake of this example, override the controller and action options:

# config/routes.rb

Rails.application.routes.draw do
  mount_ember_app :frontend, to: "/", controller: "application", action: "index"
end

When serving the EmberCLI generated index.html with the render_ember_app helper, make sure the controller's layout is disabled, as EmberCLI generates a fully-formed HTML document:

# app/controllers/application.rb
class ApplicationController < ActionController::Base
  def index
    render layout: false
  end
end

Rendering the EmberCLI generated JS and CSS

Rendering EmberCLI applications with render_ember_app is the recommended, actively supported method of serving EmberCLI applications.

However, for the sake of backwards compatibility, ember-cli-rails supports injecting the EmberCLI-generated assets into an existing Rails layout.

Note: for Vite-based applications (generated with ember-cli >= 6.8), use include_ember_script_tags on its own. It emits everything the application needs to boot — the configuration <meta> tag, the stylesheet and modulepreload links, and the ES module script tags — extracted from the generated index.html. include_ember_stylesheet_tags only supports classic (Broccoli-based) applications.

When the application is served by Vite's development server, include_ember_script_tags (from [ember-cli-rails-assets]) reads index.html from the server and emits the startup tags with absolute URLs pointing at it — nothing is built, and changes to the application are picked up by reloading the page.

With the development server disabled (dev_server: false), the helpers read the output of ember build instead: the application is built once, synchronously, on the first request, and changes to it are only picked up by restarting the Rails server.

Following the example above, configure the mounted EmberCLI application to be served by a custom controller (ApplicationController, in this case).

In the corresponding view, use the asset helpers:

<%= include_ember_script_tags :frontend %>
<%= include_ember_stylesheet_tags :frontend %>

Mounting multiple Ember applications

Rendering Ember applications to paths other than / requires additional configuration.

Consider a scenario where you had Ember applications named frontend and admin_panel, served from / and /admin_panel respectively.

First, specify the Ember applications in the initializer:

EmberCli.configure do |c|
  c.app :frontend
  c.app :admin_panel, path: "path/to/admin_ember_app"
end

Next, mount the applications alongside the rest of Rails' routes. Note that admin_panel route is added before the frontend route because it's more specific:

# /config/routes.rb
Rails.application.routes.draw do
  mount_ember_app :admin_panel, to: "/admin_panel"
  mount_ember_app :frontend, to: "/"
end

The index.html of a Vite build refers to its assets with root-relative URLs. When the application is served from the build output, mount_ember_app remaps those references onto the mount point, where the assets are served — references that already carry the mount point, from a rootURL configured to match it, are left alone. Development-server-backed applications are unaffected: their asset URLs point at the development server absolutely.

For classic (Broccoli-based) applications, set each Ember application's rootURL to the mount point:

// frontend/config/environment.js

module.exports = function(environment) {
  var ENV = {
    modulePrefix: 'frontend',
    environment: environment,
    rootURL: '/',
    // ...
  }
};

// path/to/admin_ember_app/config/environment.js

module.exports = function(environment) {
  var ENV = {
    modulePrefix: 'admin_panel',
    environment: environment,
    rootURL: '/admin_panel',  // originally '/'
    // ...
  }
};

Finally, configure EmberCLI's fingerprinting to prepend the mount point to the application's assets:

// frontend/ember-cli-build.js

module.exports = function(defaults) {
  var app = new EmberApp(defaults, {
    fingerprint: {
      // matches the `/` mount point
      prepend: 'https://cdn.example.com/',
    }
  });
};


// path/to/admin_ember_app/ember-cli-build.js

module.exports = function(defaults) {
  var app = new EmberApp(defaults, {
    fingerprint: {
      // matches the `/admin_panel` mount point
      prepend: 'https://cdn.example.com/admin_panel/',
    }
  });
};

When injecting the EmberCLI-generated assets with the include_ember_script_tags and include_ember_stylesheet_tags helpers to a path other than "/", a <base> tag must also be injected with a corresponding href value:

<base href="/">
<%= include_ember_script_tags :frontend %>
<%= include_ember_stylesheet_tags :frontend %>

<base href="/admin_panel/">
<%= include_ember_script_tags :admin_panel %>
<%= include_ember_stylesheet_tags :admin_panel %>

If you're using the include_ember style helpers with a single-page Ember application that defers routing to the Rails application, insert a call to mount_ember_assets at the bottom of your routes file to serve the EmberCLI-generated assets:

# config/routes.rb
Rails.application.routes.draw do
  mount_ember_assets :frontend, to: "/"
end

CSRF Tokens

Your Rails controllers, by default, expect a valid authenticity token to be submitted along with non-GET requests.

Without the authenticity token, requests will respond with 422 Unprocessable Entity errors (specifically ActionController::InvalidAuthenticityToken).

To add the necessary tokens to requests, inject the csrf_meta_tags into the template:

<!-- app/views/application/index.html.erb -->
<%= render_ember_app :frontend do |head| %>
  <% head.append do %>
    <%= csrf_meta_tags %>
  <% end %>
<% end %>

The default EmberCli::EmberController and the default view handle behave like this by default.

If an Ember application is mounted with another controller, it should append the CSRF tags to its view's <head>.

ember-cli-rails-addon configures your Ember application to make HTTP requests with the injected CSRF tokens in the X-CSRF-TOKEN header.

Serving from multi-process servers in development

If you're using a multi-process server (Puma, Unicorn, etc.) in development, make sure it's configured to run a single worker process.

Without restricting the server to a single process, it is possible for multiple EmberCLI runners to clobber each others' work.

This does not apply to Vite-based applications served by Vite's development server: nothing is written to a shared build directory. Give the application a fixed port so that the workers share a single development server rather than starting one each.

SKIP_EMBER

If set on the environment, SKIP_EMBER will configure ember-cli-rails to skip the build step entirely. This is useful if you're using an alternative deployment strategy in the test or development environment. By default, ember-cli-rails will skip the build step in production-like environments.

EMBER_ENV

If set on the environment, the value of EMBER_ENV will be passed to the ember process as the value of the --environment flag.

If EMBER_ENV is unspecified, the current Rails environment will be passed to the ember process, with the exception of non-standard Rails environments, which will be replaced with production.

RAILS_ENV

While being managed by EmberCLI Rails, EmberCLI process will have access to the RAILS_ENV environment variable. This can be helpful to detect the Rails environment from within the EmberCLI process.

This can be useful to determine whether or not EmberCLI is running in its own standalone process or being managed by Rails.

For example, to enable ember-cli-mirage API responses in development while being run outside of Rails (while run by ember serve), check for the absence of the RAILS_ENV environment variable:

// config/environment.js
if (environment === 'development') {
  ENV['ember-cli-mirage'] = {
    enabled: typeof process.env.RAILS_ENV === 'undefined',
  }
}

RAILS_ENV will be absent in production builds.

EmberCLI support

This project supports:

• EmberCLI versions >= 1.13.13 using the classic (Broccoli-based) build, together with ember-cli-rails-addon
• EmberCLI versions >= 6.8 using the Vite-based build, without the addon

The test suite currently exercises the 5.12.x and 6.7.x (classic) and 7.0.x (Vite) series.

Note the following limitations for Vite-based applications:

• include_ember_script_tags emits the full set of tags the application needs to boot, stylesheets included; include_ember_stylesheet_tags is classic-only and must not be called for Vite-based applications
• in development, the application is served by Vite's development server rather than out of a build directory. The asset helpers serve their tags from the development server too; with dev_server: false they read the build output, which is built once, synchronously, on the first request

Ruby and Rails support

This project supports:

• Ruby versions >= 2.5.0
• Rails versions >=5.2.x.

To learn more about supported versions and upgrades, read the upgrading guide.

Contributing

See the CONTRIBUTING document. Thank you, contributors!

License

Open source templates are Copyright (c) 2015 thoughtbot, inc. It contains free software that may be redistributed under the terms specified in the LICENSE file.

About

ember-cli-rails was originally created by Pavel Pravosud and Jonathan Jackson.

ember-cli-rails is maintained by Sean Doyle, Jonathan Jackson and Ryunosuke Sato.