Question

I wish to precompile all the CSS and JS files in my project’s app/assets folder. I do NOT want to precompile everything in vendor/assets or lib/assets, only the dependencies of my files as needed.

I tried the following wildcard setting, but it incorrectly precompiles everything. This results in lots of extra work and even causes a compilation failure when using bootstrap-sass.

config.assets.precompile += ['*.js', '*.css']

What is my best bet to only process my files in app/assets? Thanks!

Answer 1

This task is made more difficult by the fact that sprockets works with logical paths that do not include where the underlying, uncompiled resourced is located.

Suppose my project has the JS file “/app/assets/javascripts/foo/bar.js.coffee”.

The sprockets compiler will first determine the output file extension, in this case “.js”, and then the evaluate whether or not to compile the logical path “foo/bar.js”. The uncompiled resource could be in “app/assets/javascripts”, “vendor/assets/javascripts”, “lib/assets/javascripts” or a gem, so there is no way to include/exclude a particular file based on the logical path alone.

To determine where the underlying resource is located, I believe it is necessary to ask the sprockets environment (available via the object Rails.application.assets) to resolve the real path of the resource given the logical path.

Here is the solution that I am using. I am fairly new to Ruby so this is not the most elegant code:

# In production.rb
config.assets.precompile << Proc.new { |path|
  if path =~ /\.(css|js)\z/
    full_path = Rails.application.assets.resolve(path).to_path
    app_assets_path = Rails.root.join('app', 'assets').to_path
    if full_path.starts_with? app_assets_path
      puts "including asset: " + full_path
      true
    else
      puts "excluding asset: " + full_path
      false
    end
  else
    false
  end
}

---

With sprockets > 3.0, this will not work in production because Rails.application.assets will be nil (assuming default: config.assets.compile = false).

To workaround you replace the full_path assignment with:

@assets ||= Rails.application.assets || Sprockets::Railtie.build_environment(Rails.application)
full_path = @assets.resolve(path)

See also: https://github.com/rails/sprockets-rails/issues/237