Rails helper method that determines if an asset exists

application.html.haml

- if asset_exists? "#{params[:controller]}.css"
  = stylesheet_link_tag params[:controller]

- if asset_exists? "#{params[:controller]}.js"
  = javascript_include_tag params[:controller]

application_helper.rb

# Returns true if an asset exists in the Asset Pipeline, false if not.
def asset_exists?(path)
  begin
    pathname = Rails.application.assets.resolve(path)
    return !!pathname # double-bang turns String into boolean
  rescue Sprockets::FileNotFound
    return false
  end
end

Possibly more efficient: Rails.application.assets.find_asset(path).nil?

With Rails 5 / Sprockets 3.7 this works too:

def asset_exists?(path)
  Rails.application.assets.resolve(path).present? 
end

The resolve method will return nil, whereas resolve! will throw an exception.