ZJIT: undefined method for nil on Rails 8.1.2 app #943
Description
I encountered subtle errors on a new Rails 8.1.2 app with ZJIT, such as:
error on Puma (click to expand)
``` Puma caught this error: undefined method 'group_by' for nil (NoMethodError) /Users/hachi8833/.anyenv/envs/rbenv/versions/4.0.1/lib/ruby/gems/4.0.0/gems/actionpack-8.1.2/lib/action_dispatch/middleware/server_timing.rb:66:in 'ActionDispatch::ServerTiming#call' /Users/hachi8833/.anyenv/envs/rbenv/versions/4.0.1/lib/ruby/gems/4.0.0/gems/rails_live_reload-0.5.0/lib/rails_live_reload/middleware/base.rb:19:in 'RailsLiveReload::Middleware::Base#call!' /Users/hachi8833/.anyenv/envs/rbenv/versions/4.0.1/lib/ruby/gems/4.0.0/gems/rails_live_reload-0.5.0/lib/rails_live_reload/middleware/base.rb:9:in 'RailsLiveReload::Middleware::Base#call' /Users/hachi8833/.anyenv/envs/rbenv/versions/4.0.1/lib/ruby/gems/4.0.0/gems/actionpack-8.1.2/lib/action_dispatch/middleware/executor.rb:20:in 'ActionDispatch::Executor#call' /Users/hachi8833/.anyenv/envs/rbenv/versions/4.0.1/lib/ruby/gems/4.0.0/gems/propshaft-1.3.1/lib/propshaft/server.rb:37:in 'Propshaft::Server#call' /Users/hachi8833/.anyenv/envs/rbenv/versions/4.0.1/lib/ruby/gems/4.0.0/gems/actionpack-8.1.2/lib/action_dispatch/middleware/static.rb:27:in 'ActionDispatch::Static#call' /Users/hachi8833/.anyenv/envs/rbenv/versions/4.0.1/lib/ruby/gems/4.0.0/gems/rack-3.2.4/lib/rack/sendfile.rb:131:in 'Rack::Sendfile#call' /Users/hachi8833/.anyenv/envs/rbenv/versions/4.0.1/lib/ruby/gems/4.0.0/gems/actionpack-8.1.2/lib/action_dispatch/middleware/host_authorization.rb:143:in 'ActionDispatch::HostAuthorization#call' /Users/hachi8833/.anyenv/envs/rbenv/versions/4.0.1/lib/ruby/gems/4.0.0/gems/rack-mini-profiler-4.0.1/lib/mini_profiler.rb:334:in 'Rack::MiniProfiler#call' /Users/hachi8833/.anyenv/envs/rbenv/versions/4.0.1/lib/ruby/gems/4.0.0/gems/railties-8.1.2/lib/rails/engine.rb:534:in 'Rails::Engine#call' /Users/hachi8833/.anyenv/envs/rbenv/versions/4.0.1/lib/ruby/gems/4.0.0/gems/puma-7.2.0/lib/puma/configuration.rb:296:in 'Puma::Configuration::ConfigMiddleware#call' /Users/hachi8833/.anyenv/envs/rbenv/versions/4.0.1/lib/ruby/gems/4.0.0/gems/puma-7.2.0/lib/puma/request.rb:103:in 'block in Puma::Request#handle_request' /Users/hachi8833/.anyenv/envs/rbenv/versions/4.0.1/lib/ruby/gems/4.0.0/gems/puma-7.2.0/lib/puma/thread_pool.rb:355:in 'Puma::ThreadPool#with_force_shutdown' /Users/hachi8833/.anyenv/envs/rbenv/versions/4.0.1/lib/ruby/gems/4.0.0/gems/puma-7.2.0/lib/puma/request.rb:102:in 'Puma::Request#handle_request' /Users/hachi8833/.anyenv/envs/rbenv/versions/4.0.1/lib/ruby/gems/4.0.0/gems/puma-7.2.0/lib/puma/server.rb:503:in 'Puma::Server#process_client' /Users/hachi8833/.anyenv/envs/rbenv/versions/4.0.1/lib/ruby/gems/4.0.0/gems/puma-7.2.0/lib/puma/server.rb:262:in 'block in Puma::Server#run' /Users/hachi8833/.anyenv/envs/rbenv/versions/4.0.1/lib/ruby/gems/4.0.0/gems/puma-7.2.0/lib/puma/thread_pool.rb:182:in 'block in Puma::ThreadPool#spawn_thread' ```or
Please find the following repo fore reproduction:
As noted on README, Ruby 4.0.1 YJIT does not cause the errors.
It seems the behaviors of Puma (uma::Request#fast_write_str), Lookbook and ActionView (ActionView::OutputBuffer), and ServerTiming middleware are affected by ZJIT: some values are unexpectedly turns into nil...
The repo contains to_suppress_errors branch to apply some patches to suppress errors (Gemini 4 Pro created).
Hope this helps you to fix the subtle bugs 🙏