YUI CSS Compression fails with version 5.0.2

[volontarian]

YUI CSS Compression fails with version 5.0.2 at assets precompilation process.

I created a sample application to reproduce the error: https://github.com/gawlista/jquery-ui-rails-5-compression-fails
There are 2 commits:

• first commit includes the Rails generator results and
• second commit includes customization which let css compression fail.

You get the Error with the following command:

RAILS_ENV=staging RAILS_GROUPS=assets bundle exec rake assets:precompile --trace

administorsmini:jquery-ui-rails-5-compression-fails gawlim$ RAILS_ENV=staging RAILS_GROUPS=assets bundle exec rake assets:precompile --trace
** Invoke assets:precompile (first_time)
** Invoke assets:environment (first_time)
** Execute assets:environment
** Invoke environment (first_time)
** Execute environment
** Execute assets:precompile
rake aborted!
YUI::Compressor::RuntimeError: compression failed
  (in /Users/gawlim/workspace/reproduction/jquery-ui-rails-5-compression-fails/app/assets/stylesheets/application.css.sass)
/Users/gawlim/.rbenv/versions/2.1.1/lib/ruby/gems/2.1.0/gems/yui-compressor-0.9.6/lib/yui/compressor.rb:87:in `block in compress'
/Users/gawlim/.rbenv/versions/2.1.1/lib/ruby/gems/2.1.0/gems/yui-compressor-0.9.6/lib/yui/compressor.rb:117:in `streamify'
/Users/gawlim/.rbenv/versions/2.1.1/lib/ruby/gems/2.1.0/gems/yui-compressor-0.9.6/lib/yui/compressor.rb:66:in `compress'
/Users/gawlim/.rbenv/versions/2.1.1/lib/ruby/gems/2.1.0/gems/sprockets-2.11.3/lib/sprockets/yui_compressor.rb:21:in `evaluate'
/Users/gawlim/.rbenv/versions/2.1.1/lib/ruby/gems/2.1.0/gems/tilt-1.4.1/lib/tilt/template.rb:103:in `render'
/Users/gawlim/.rbenv/versions/2.1.1/lib/ruby/gems/2.1.0/gems/sprockets-2.11.3/lib/sprockets/context.rb:197:in `block in evaluate'
/Users/gawlim/.rbenv/versions/2.1.1/lib/ruby/gems/2.1.0/gems/sprockets-2.11.3/lib/sprockets/context.rb:194:in `each'
/Users/gawlim/.rbenv/versions/2.1.1/lib/ruby/gems/2.1.0/gems/sprockets-2.11.3/lib/sprockets/context.rb:194:in `evaluate'
/Users/gawlim/.rbenv/versions/2.1.1/lib/ruby/gems/2.1.0/gems/sprockets-2.11.3/lib/sprockets/bundled_asset.rb:25:in `initialize'
/Users/gawlim/.rbenv/versions/2.1.1/lib/ruby/gems/2.1.0/gems/sprockets-2.11.3/lib/sprockets/base.rb:377:in `new'
/Users/gawlim/.rbenv/versions/2.1.1/lib/ruby/gems/2.1.0/gems/sprockets-2.11.3/lib/sprockets/base.rb:377:in `build_asset'
/Users/gawlim/.rbenv/versions/2.1.1/lib/ruby/gems/2.1.0/gems/sprockets-2.11.3/lib/sprockets/index.rb:94:in `block in build_asset'
/Users/gawlim/.rbenv/versions/2.1.1/lib/ruby/gems/2.1.0/gems/sprockets-2.11.3/lib/sprockets/caching.rb:58:in `cache_asset'
/Users/gawlim/.rbenv/versions/2.1.1/lib/ruby/gems/2.1.0/gems/sprockets-2.11.3/lib/sprockets/index.rb:93:in `build_asset'
/Users/gawlim/.rbenv/versions/2.1.1/lib/ruby/gems/2.1.0/gems/sprockets-2.11.3/lib/sprockets/base.rb:287:in `find_asset'
/Users/gawlim/.rbenv/versions/2.1.1/lib/ruby/gems/2.1.0/gems/sprockets-2.11.3/lib/sprockets/index.rb:61:in `find_asset'
/Users/gawlim/.rbenv/versions/2.1.1/lib/ruby/gems/2.1.0/gems/sprockets-2.11.3/lib/sprockets/manifest.rb:211:in `block in find_asset'
/Users/gawlim/.rbenv/versions/2.1.1/lib/ruby/gems/2.1.0/gems/sprockets-2.11.3/lib/sprockets/manifest.rb:257:in `benchmark'
/Users/gawlim/.rbenv/versions/2.1.1/lib/ruby/gems/2.1.0/gems/sprockets-2.11.3/lib/sprockets/manifest.rb:210:in `find_asset'
/Users/gawlim/.rbenv/versions/2.1.1/lib/ruby/gems/2.1.0/gems/sprockets-2.11.3/lib/sprockets/manifest.rb:119:in `block in compile'
/Users/gawlim/.rbenv/versions/2.1.1/lib/ruby/gems/2.1.0/gems/sprockets-2.11.3/lib/sprockets/manifest.rb:118:in `each'
/Users/gawlim/.rbenv/versions/2.1.1/lib/ruby/gems/2.1.0/gems/sprockets-2.11.3/lib/sprockets/manifest.rb:118:in `compile'
/Users/gawlim/.rbenv/versions/2.1.1/lib/ruby/gems/2.1.0/gems/sprockets-rails-2.2.0/lib/sprockets/rails/task.rb:70:in `block (3 levels) in define'
/Users/gawlim/.rbenv/versions/2.1.1/lib/ruby/gems/2.1.0/gems/sprockets-2.11.3/lib/rake/sprocketstask.rb:146:in `with_logger'
/Users/gawlim/.rbenv/versions/2.1.1/lib/ruby/gems/2.1.0/gems/sprockets-rails-2.2.0/lib/sprockets/rails/task.rb:69:in `block (2 levels) in define'
/Users/gawlim/.rbenv/versions/2.1.1/lib/ruby/gems/2.1.0/gems/rake-10.3.2/lib/rake/task.rb:240:in `call'
/Users/gawlim/.rbenv/versions/2.1.1/lib/ruby/gems/2.1.0/gems/rake-10.3.2/lib/rake/task.rb:240:in `block in execute'
/Users/gawlim/.rbenv/versions/2.1.1/lib/ruby/gems/2.1.0/gems/rake-10.3.2/lib/rake/task.rb:235:in `each'
/Users/gawlim/.rbenv/versions/2.1.1/lib/ruby/gems/2.1.0/gems/rake-10.3.2/lib/rake/task.rb:235:in `execute'
/Users/gawlim/.rbenv/versions/2.1.1/lib/ruby/gems/2.1.0/gems/rake-10.3.2/lib/rake/task.rb:179:in `block in invoke_with_call_chain'
/Users/gawlim/.rbenv/versions/2.1.1/lib/ruby/2.1.0/monitor.rb:211:in `mon_synchronize'
/Users/gawlim/.rbenv/versions/2.1.1/lib/ruby/gems/2.1.0/gems/rake-10.3.2/lib/rake/task.rb:172:in `invoke_with_call_chain'
/Users/gawlim/.rbenv/versions/2.1.1/lib/ruby/gems/2.1.0/gems/rake-10.3.2/lib/rake/task.rb:165:in `invoke'
/Users/gawlim/.rbenv/versions/2.1.1/lib/ruby/gems/2.1.0/gems/rake-10.3.2/lib/rake/application.rb:150:in `invoke_task'
/Users/gawlim/.rbenv/versions/2.1.1/lib/ruby/gems/2.1.0/gems/rake-10.3.2/lib/rake/application.rb:106:in `block (2 levels) in top_level'
/Users/gawlim/.rbenv/versions/2.1.1/lib/ruby/gems/2.1.0/gems/rake-10.3.2/lib/rake/application.rb:106:in `each'
/Users/gawlim/.rbenv/versions/2.1.1/lib/ruby/gems/2.1.0/gems/rake-10.3.2/lib/rake/application.rb:106:in `block in top_level'
/Users/gawlim/.rbenv/versions/2.1.1/lib/ruby/gems/2.1.0/gems/rake-10.3.2/lib/rake/application.rb:115:in `run_with_threads'
/Users/gawlim/.rbenv/versions/2.1.1/lib/ruby/gems/2.1.0/gems/rake-10.3.2/lib/rake/application.rb:100:in `top_level'
/Users/gawlim/.rbenv/versions/2.1.1/lib/ruby/gems/2.1.0/gems/rake-10.3.2/lib/rake/application.rb:78:in `block in run'
/Users/gawlim/.rbenv/versions/2.1.1/lib/ruby/gems/2.1.0/gems/rake-10.3.2/lib/rake/application.rb:176:in `standard_exception_handling'
/Users/gawlim/.rbenv/versions/2.1.1/lib/ruby/gems/2.1.0/gems/rake-10.3.2/lib/rake/application.rb:75:in `run'
/Users/gawlim/.rbenv/versions/2.1.1/lib/ruby/gems/2.1.0/gems/rake-10.3.2/bin/rake:33:in `<top (required)>'
/Users/gawlim/.rbenv/versions/2.1.1/bin/rake:23:in `load'
/Users/gawlim/.rbenv/versions/2.1.1/bin/rake:23:in `<main>'
Tasks: TOP => assets:precompile

With a application.css like this instead of a Sass file it still fails like before:

*= require_tree .
*= require jquery-ui
*= require_self

How to handle this?

[volontarian]

I've updated the yui-compressor gem to latest version 0.12.0. Now it works :-)