sass-rails helpers "image-url", "asset-url" are not working in rails 3.2.1

Despite what the documentation says, it seems the default options in rails 3.2.6 allow you to just make things work with even less path information in your CSS.E.g. ../app/assets/images/rails.png is references in your example.css.scss file with something like:

background: white url(rails.png) repeat-y;

You don't include the image-url or asset-url into your scss (as far as I know), just plain url(your_image.png). That bit of documentation appears to be just an explanation of what it is doing in the background.

When I hit this problem, it was because I had not included the css file in the asset pipeline for pre-compilation. As a result, it would be generated at runtime. Because the sass-rails gem is commonly in the :assets group, the helpers are unavailable when generating css files at runtime.

Try adding the following line to your application.rb (or production.rb):

config.assets.precompile += %w( public/omg.css )

I found the fix on this post including a gotcha around naming the files when adding them to the precompiler.

If you have updated your app to Rails 3.1 in the past, make sure you changed your application.rb file from

# If you have a Gemfile, require the gems listed there, including any gems# you've limited to :test, :development, or :production.Bundler.require(:default, Rails.env) if defined?(Bundler)

to

if defined?(Bundler)  # If you precompile assets before deploying to production, use this line  Bundler.require *Rails.groups(:assets => %w(development test))  # If you want your assets lazily compiled in production, use this line  # Bundler.require(:default, :assets, Rails.env)end

See this railscast on upgrading to Rails 3.1 and adding the asset pipeline.

Update: Rails 4 goes back to the old way of doing it. Thanks Aaron Gray!

# Require the gems listed in Gemfile, including any gems# you've limited to :test, :development, or :production.Bundler.require(:default, Rails.env)