Condenser Rails

Provides Condenser integration for the Rails Asset Pipeline.

Requires Condenser 2.0, Ruby 3.3 or newer, Rails 8.0 or newer, and Node wherever assets are compiled. Upgrading from an earlier version? See Upgrading to Condenser 2.

gem 'condenser-rails'
gem 'sass-embedded'                     # Sass and SCSS
gem 'lightningcss', '>= 1.33.0.2'       # the default CSS minifier

Or alternatively require 'condenser/railtie' in your config/application.rb if you have Bundler auto-require disabled.

Sass and SCSS are compiled with Sass Embedded. CSS is minified with Lightning CSS; lightningcss isn't needed if config.assets.css_minifier is :sass or nil.

JavaScript is bundled, and minified, with Rolldown by default. Rolldown runs in Node, so Node must be installed wherever assets are compiled. The rolldown npm package is installed into the npm path (config.assets.npm_path, Rails.root by default) the first time it's needed.

To configure Rolldown, replace the default exporter with a configured Condenser::RolldownProcessor instance. Registering the class, as in earlier versions, no longer works. Pass minify: yourself, since it defaults to false:

config.assets.configure do |app, env|
  env.unregister_exporter('application/javascript', Condenser::RolldownProcessor)
  env.register_exporter('application/javascript', Condenser::RolldownProcessor.new(env.npm_path,
    minify: !Rails.env.local?,
    aliases: { 'jquery' => app.root.join('vendor/assets/javascripts/jquery.js').to_s }
  ))
end

Rollup is deprecated, and will be removed in Condenser 3. To use it instead of Rolldown:

config.assets.configure do |app, env|
  env.unregister_exporter('application/javascript')
  env.register_exporter('application/javascript', Condenser::RollupProcessor)
end

rake assets:precompile

Deployment task that compiles any assets listed in config.assets.precompile to public/assets.

rake assets:clean

Removes old assets from public/assets. Useful when doing rolling deploys that may still be serving old assets while the new ones are being compiled.

rake assets:clobber

Nuke public/assets and remove config/manifest.json.

config.assets.precompile

Add additional assets to compile on deploy. Defaults to application.js, application.css and any .jpg, .png, or .gif files under app/assets.

config.assets.path

Add additional load paths to this Array. Rails includes app/assets, lib/assets and vendor/assets for you already. Plugins might want to add their custom paths to this.

config.assets.prefix

Defaults to /assets. Changes the directory to compile assets to.

config.assets.compile

Enables the Condenser compile environment. If disabled, Rails.application.assets will be nil to prevent inadvertent compilation calls. View helpers will depend on assets being precompiled to public/assets in order to link to them. Initializers expecting Rails.application.assets during boot should be accessing the environment in a config.assets.configure block. See below.

config.assets.npm_path

The directory npm packages, such as rolldown, are installed into and loaded from. Defaults to Rails.root.

config.assets.watch

Directories, relative to Rails.root or absolute, that a running server watches for changes to files assets depend on, without adding them to the load path. Defaults to ['config']; missing directories are skipped. A depends_on path starting with ! is a file relative to Rails.root, and only rebuilds a running server's assets when it's under a load path or a watched directory:

// depends_on !config/foo.yml
const foo = <%= YAML.load_file(Rails.root.join('config/foo.yml')).to_json %>;

config.assets.watch << 'data'

config.assets.js_minifier

The JS minifier to use to minify javascript sources. Valid options are :rolldown (the default, Rolldown minifies its own output), :terser, your own minifier, and false or nil to disable minification. :terser runs in Node, is npm-installed into the npm path when first used, and turns Rolldown's minifier off.

config.assets.css_minifier

The CSS minifier to use to minify css sources. Valid options are :lightning_css (the default, which needs the lightningcss gem), :sass (which needs the sass-embedded gem), your own minifier, and false or nil to disable minification.

Assets are only minified outside the development and test environments.

config.assets.compressors

A list of compressors to compress the output with. Each file will be written along with a compressed version for each compressor. Default is [:zlib] which will add a .gz version of each file. Valid options are :zlib, and :brotli. To disable set this to an empty array or false.

Optionally you may also set this to your own compressor.

config.assets.configure

Invokes block with environment when the environment is initialized. Allows direct access to the environment instance and lets you lazily load libraries only needed for asset compiling.

config.assets.configure do |app, env|
  require 'my_processor'
  env.register_preprocessor 'application/javascript', MyProcessor
end

Condenser adds support for subresource integrity checks.

javascript_include_tag :application, integrity: true
# => "<script src="/assets/application.js" integrity="sha256-TvVUHzSfftWg1rcfL6TIJ0XKEGrgLyEq6lEpcmrG9qs="></script>"

The hash is added whenever integrity: true is passed, over HTTP as well as HTTPS.

• Requires Condenser 2.0, Ruby 3.3 or newer, Rails 8.0 or newer, and Node wherever assets are compiled.
• Replace gem 'sassc' with gem 'sass-embedded', and add gem 'lightningcss', '>= 1.33.0.2' unless config.assets.css_minifier is :sass or nil.
• JavaScript is bundled and minified by Rolldown by default. :uglify is removed; :terser still works, and turns Rolldown's minifier off.
• CSS is minified by Lightning CSS by default.
• A custom Rolldown exporter must be an instance: Condenser::RolldownProcessor.new(env.npm_path, minify: !Rails.env.local?, …).
• A bare // depends_on path that matches nothing now raises Condenser::FileNotFound (globs don't). Files relative to the app root need a !, e.g. // depends_on !config/foo.yml. config/ is watched by default so a running server picks up changes to them.
• A JavaScript import that can't be resolved now fails the build.
• JSON files can be imported from JavaScript, e.g. import data from 'data.json'.
• Sass @use and @import of npm packages pick the package's stylesheet from its exports (sass or style condition), sass or style field.
• A configured config.assets.npm_path is now respected instead of being reset to Rails.root.
• Clear tmp/cache/assets and public/assets after upgrading.

Condenser Rails is released under the MIT License.