Sporadic errors "LoadError: no such file to load -- sass" with JRuby and Sprockets

[chadlwilson]

I'm not really sure what is going on here, but would appreciate any tips - please go gentle, I'm not a Rails/Sprockets expert 😅. Apologies if this should be reported at the other project; I'm not really sure.

When working in development mode with hot-reloading and the autoloader, every now and then (but reasonably frequently) I get the below error. I can't work out a pattern as to what is happening. When this happens the browser will block. If I kill the request and try again it will usually work OK but then occur again later.

I have also had it happen when pre-compiling assets too, so perhaps it is to do with some kind of race condition or threading type of issue with JRuby or sprockets? If you suspect I need to upgrade to Sprockets 4, that's fine. Haven't noticed a similar issue earlier when using ruby-sass.

warning: thread "Ruby-0-Thread-4163: /Users/chad/Projects/community/gocd/gocd/server/src/main/webapp/WEB-INF/rails/gems/jruby/2.6.0/bundler/gems/sass-embedded-host-ruby-0d103fd1936a/lib/sass/embedded/dispatcher.rb:18" terminated with exception (report_on_exception is true):
LoadError: no such file to load -- sass
                require at org/jruby/RubyKernel.java:1017
                require at /Users/chad/Projects/community/gocd/gocd/server/src/main/webapp/WEB-INF/rails/gems/jruby/2.6.0/gems/zeitwerk-2.6.0/lib/zeitwerk/kernel.rb:35
                 <main> at /Users/chad/Projects/community/gocd/gocd/server/src/main/webapp/WEB-INF/rails/gems/jruby/2.6.0/gems/sprockets-3.7.2/lib/sprockets/autoload/sass.rb:1
                require at org/jruby/RubyKernel.java:1017
                require at /Users/chad/Projects/community/gocd/gocd/server/src/main/webapp/WEB-INF/rails/gems/jruby/2.6.0/gems/zeitwerk-2.6.0/lib/zeitwerk/kernel.rb:35
              asset_url at /Users/chad/Projects/community/gocd/gocd/server/src/main/webapp/WEB-INF/rails/gems/jruby/2.6.0/gems/sprockets-3.7.2/lib/sprockets/sass_processor.rb:137
               font_url at /Users/chad/Projects/community/gocd/gocd/server/src/main/webapp/WEB-INF/rails/gems/jruby/2.6.0/gems/sprockets-3.7.2/lib/sprockets/sass_processor.rb:209
                  setup at /Users/chad/Projects/community/gocd/gocd/server/src/main/webapp/WEB-INF/rails/gems/jruby/2.6.0/gems/sassc-embedded-1.54.0/lib/sassc/embedded.rb:151
          function_call at /Users/chad/Projects/community/gocd/gocd/server/src/main/webapp/WEB-INF/rails/gems/jruby/2.6.0/bundler/gems/sass-embedded-host-ruby-0d103fd1936a/lib/sass/embedded/host/function_registry.rb:50
  function_call_request at /Users/chad/Projects/community/gocd/gocd/server/src/main/webapp/WEB-INF/rails/gems/jruby/2.6.0/bundler/gems/sass-embedded-host-ruby-0d103fd1936a/lib/sass/embedded/host.rb:119
            public_send at org/jruby/RubyKernel.java:2003
        receive_message at /Users/chad/Projects/community/gocd/gocd/server/src/main/webapp/WEB-INF/rails/gems/jruby/2.6.0/bundler/gems/sass-embedded-host-ruby-0d103fd1936a/lib/sass/embedded/dispatcher.rb:80

Environment:
JRuby 9.3.7.0 (Ruby 2.6 compatible)
Rails 6.1.6.1 in Zeitwork mode
Sprockets 3.7.2 (haven't yet moved to 4.1, was earlier blocked by another dependency)

[ntkme]

Assuming you’re trying to use the shim for sassc, you will have to make sure all Sass related configs are referring sassc rather than sass or you may see this error.

[chadlwilson]

Hmm, that does seem similar - however doesn't seem to explain why it's mostly working just fine, but occasionally fails? We're not overriding any defaults for the css_compressor at all right now.

I did have sassc working earlier with Sprockets 3.7.x as well before switching to sass-embedded due to issues with Windows.

If you think there's something in Sprockets 4 likely required for it to be better behaved here, I suppose I'll have to try and upgrade that too. 😬

[ntkme]

Here is my educated guess: you have sassc installed, but it was never used by sprockets 3.x. You probably have sass somehow available in Ruby's $LOAD_PATH like the reporter of the other issue, so it happens to work sometimes. E.g. rake and bundle exec rake have different $LOAD_PATH.

[chadlwilson]

Ok, thanks a lot. Pretty sure I don't have sass available anywhere, but regardless will try again with Sprockets 4. 🙏

[chadlwilson]

For what it's worth, I'm still able to get this on Sprockets 4, but ran out of time to figure out what is going on. Somehow the sass_processor is being used rather than sassc_processor at times.

warning: thread "Ruby-0-Thread-1672: /Users/chad/Projects/community/gocd/gocd/server/src/main/webapp/WEB-INF/rails/gems/jruby/2.6.0/bundler/gems/sass-embedded-host-ruby-0d103fd1936a/lib/sass/embedded/dispatcher.rb:18" terminated with exception (report_on_exception is true):
LoadError: no such file to load -- sass
                require at org/jruby/RubyKernel.java:1017
                require at /Users/chad/Projects/community/gocd/gocd/server/src/main/webapp/WEB-INF/rails/gems/jruby/2.6.0/gems/zeitwerk-2.6.0/lib/zeitwerk/kernel.rb:35
                 <main> at /Users/chad/Projects/community/gocd/gocd/server/src/main/webapp/WEB-INF/rails/gems/jruby/2.6.0/gems/sprockets-4.1.1/lib/sprockets/autoload/sass.rb:2
                require at org/jruby/RubyKernel.java:1017
                require at /Users/chad/Projects/community/gocd/gocd/server/src/main/webapp/WEB-INF/rails/gems/jruby/2.6.0/gems/zeitwerk-2.6.0/lib/zeitwerk/kernel.rb:35
              asset_url at /Users/chad/Projects/community/gocd/gocd/server/src/main/webapp/WEB-INF/rails/gems/jruby/2.6.0/gems/sprockets-4.1.1/lib/sprockets/sass_processor.rb:158
              image_url at /Users/chad/Projects/community/gocd/gocd/server/src/main/webapp/WEB-INF/rails/gems/jruby/2.6.0/gems/sprockets-4.1.1/lib/sprockets/sass_processor.rb:176
                  setup at /Users/chad/Projects/community/gocd/gocd/server/src/main/webapp/WEB-INF/rails/gems/jruby/2.6.0/gems/sassc-embedded-1.54.0/lib/sassc/embedded.rb:151
          function_call at /Users/chad/Projects/community/gocd/gocd/server/src/main/webapp/WEB-INF/rails/gems/jruby/2.6.0/bundler/gems/sass-embedded-host-ruby-0d103fd1936a/lib/sass/embedded/host/function_registry.rb:50
  function_call_request at /Users/chad/Projects/community/gocd/gocd/server/src/main/webapp/WEB-INF/rails/gems/jruby/2.6.0/bundler/gems/sass-embedded-host-ruby-0d103fd1936a/lib/sass/embedded/host.rb:119
            public_send at org/jruby/RubyKernel.java:2003
        receive_message at /Users/chad/Projects/community/gocd/gocd/server/src/main/webapp/WEB-INF/rails/gems/jruby/2.6.0/bundler/gems/sass-embedded-host-ruby-0d103fd1936a/lib/sass/embedded/dispatcher.rb:80

[ntkme]

sass/sassc-rails#114 seems to be related here.

[chadlwilson]

Ahh, yes. I was wondering about that.

Funnily enough I just recently re-introduced (a couple of weeks ago) use of the assets block (we had got rid of it with the Rails 5 upgrade) - to avoid packaging the massive sassc
and dart-sass extensions/native bins during production runtime which should not be needed when one is precompiling assets. sassc in particular was adding 50MB of binaries to our installer size. During dev and assets compile they are there though, along with RAILS_GROUPS=assets and specific bundler require logic.

But I'll dig further later and try without to confirm the source of the issue and see if I can find an alternate approach.

[chadlwilson]

Sadly I still seem to be able to replicate the issue with everything outside the assets group, so I guess I need to keep digging :'(

source 'https://rubygems.org'
ruby '2.6.8'

gem 'rails'
gem 'sassc-rails'
gem 'sassc', github: 'sass/sassc-ruby', ref: 'refs/pull/233/head'
gem 'sassc-embedded'
gem 'sass-embedded', github: 'ntkme/sass-embedded-host-ruby', ref: 'main'
gem 'js-routes'
gem 'ts_routes'

# Windows does not include zoneinfo files, so bundle the tzinfo-data gem
gem 'tzinfo-data', platforms: [:mingw, :mswin, :x64_mingw, :jruby]

group :development, :test do
  # make sure to `System.setProperty("jruby.runtime.arguments", "--debug")` before opening up pry
  gem 'pry-debugger-jruby', platforms: :jruby
end

group :test do
  gem 'capybara'
  gem 'rspec-rails'
  gem 'rspec-instafail', require: false
  gem 'rspec_junit_formatter'
  gem 'rails-controller-testing'
end

[chadlwilson]

The only pattern I can find here is that

• if it fails, it always seems to happen on the first call into to a custom_function for a given render
• I can only replicate it in cases where the call that fails is a font_url call and seemingly when I change scss files that have font loading in them
• if I rescue the LoadError in embedded.rb and then keep going and recompiling the same file, it seems to become very difficult to replicate after that. No idea why.

Still no real ideas though.

[ntkme]

Here is how it works:

1. Sprockets::SassProcessor::SassFunctions, which is equivelent to Sprockets::SassFunctions, are created for sass: https://github.com/rails/sprockets/blob/f4d3dae71ef29c44b75a49cfbf8032cce07b423a/lib/sprockets/sass_processor.rb#L110
2. Sprockets::SassFunctions has one function added, for sassc https://github.com/sass/sassc-rails/blob/master/lib/sassc/rails/functions.rb
3. SassC::Rails::SassTemplate::Functions, this redefines functions created for sass and changes them to sassc: https://github.com/sass/sassc-rails/blob/8d0462d54b5b5dd84cb1df31823c3afaebb64534/lib/sassc/rails/template.rb#L85 https://github.com/sass/sassc-rails/blob/8d0462d54b5b5dd84cb1df31823c3afaebb64534/lib/sassc/rails/template.rb#L15

Step 3 is supposed to override the functions defined in step 1 to prevent calling sass, I think what happened is a loading order issue that step 1 happened after step 3 for some reasons. Or somehow step 3 is not happening.

[ntkme]

If you can add some log in the 3 files that have been mentioned above, and see how they are getting loaded, I think it will help understand the problem.

[chadlwilson]

I tried a bit of logging in the various files, in initializers, and in the asset_url calls, but I couldn't really see anything being re-loaded or anything weird like that after first start.

I'd just see a single call in the about-to-fail compile to a non-overridden Sprockets::SassProcessor.asset_url rather than the redefined one in SassC::Rails::SassTemplate::Functions.asset_url as for the "OK" compiles. Possibly reaching the limits of my knowledge for digging into Ruby-land right now unless I put in quite a bit more time investment. Hmm.

It's also quite possible it has nothing to do with sassc-embedded-shim-ruby and is thus a waste of your time, which is not my intention!