`const_get': uninitialized constant [class] (NameError)` after file save in Docker with Spring

Question

I'm using rails in Docker with Spring and Guard. See Guardfile:

guard 'rspec', cmd: "#{env_vars} spring rspec -color -f doc", :all_on_start => false, :all_after_pass => false do watch(%r{^spec/.+_spec\.rb$})

Weird problem: when the spring tag is in place in the above command, I get an error when I run specs, but only after I've saved a file in the container in some way. This is the error:

/usr/local/bundle/gems/activesupport-5.0.1/lib/active_support/inflector/methods.rb:268:in `const_get': uninitialized constant User (NameError)
from /usr/local/bundle/gems/activesupport-5.0.1/lib/active_support/inflector/methods.rb:268:in `block in constantize'
from /usr/local/bundle/gems/activesupport-5.0.1/lib/active_support/inflector/methods.rb:266:in `each'
from /usr/local/bundle/gems/activesupport-5.0.1/lib/active_support/inflector/methods.rb:266:in `inject'
from /usr/local/bundle/gems/activesupport-5.0.1/lib/active_support/inflector/methods.rb:266:in `constantize'
from /usr/local/bundle/gems/activesupport-5.0.1/lib/active_support/dependencies.rb:583:in `get'
from /usr/local/bundle/gems/activesupport-5.0.1/lib/active_support/dependencies.rb:614:in `constantize'
from /usr/local/bundle/gems/devise-4.2.0/lib/devise.rb:301:in `get'
from /usr/local/bundle/gems/devise-4.2.0/lib/devise/mapping.rb:81:in `to'
from /usr/local/bundle/gems/devise-4.2.0/lib/devise/mapping.rb:76:in `modules'
from /usr/local/bundle/gems/devise-4.2.0/lib/devise/mapping.rb:93:in `routes'
from /usr/local/bundle/gems/devise-4.2.0/lib/devise/mapping.rb:160:in `default_used_route'
from /usr/local/bundle/gems/devise-4.2.0/lib/devise/mapping.rb:70:in `initialize'
from /usr/local/bundle/gems/devise-4.2.0/lib/devise.rb:331:in `new'
from /usr/local/bundle/gems/devise-4.2.0/lib/devise.rb:331:in `add_mapping'
from /usr/local/bundle/gems/devise-4.2.0/lib/devise/rails/routes.rb:241:in `block in devise_for'
from /usr/local/bundle/gems/devise-4.2.0/lib/devise/rails/routes.rb:240:in `each'
from /usr/local/bundle/gems/devise-4.2.0/lib/devise/rails/routes.rb:240:in `devise_for'
from /usr/src/app/config/routes.rb:34:in `block in <top (required)>'
from /usr/local/bundle/gems/actionpack-5.0.1/lib/action_dispatch/routing/route_set.rb:389:in `instance_exec'
from /usr/local/bundle/gems/actionpack-5.0.1/lib/action_dispatch/routing/route_set.rb:389:in `eval_block'
from /usr/local/bundle/gems/actionpack-5.0.1/lib/action_dispatch/routing/route_set.rb:371:in `draw'
from /usr/src/app/config/routes.rb:1:in `<top (required)>'
from /usr/local/bundle/gems/railties-5.0.1/lib/rails/application/routes_reloader.rb:40:in `load'
from /usr/local/bundle/gems/railties-5.0.1/lib/rails/application/routes_reloader.rb:40:in `block in load_paths'
from /usr/local/bundle/gems/railties-5.0.1/lib/rails/application/routes_reloader.rb:40:in `each'
from /usr/local/bundle/gems/railties-5.0.1/lib/rails/application/routes_reloader.rb:40:in `load_paths'
from /usr/local/bundle/gems/railties-5.0.1/lib/rails/application/routes_reloader.rb:16:in `reload!'
from /usr/local/bundle/gems/railties-5.0.1/lib/rails/application/routes_reloader.rb:26:in `block in updater'
from /usr/local/bundle/gems/activesupport-5.0.1/lib/active_support/file_update_checker.rb:77:in `call'
from /usr/local/bundle/gems/activesupport-5.0.1/lib/active_support/file_update_checker.rb:77:in `execute'
from /usr/local/bundle/gems/railties-5.0.1/lib/rails/application/routes_reloader.rb:7:in `execute'
from /usr/local/bundle/gems/railties-5.0.1/lib/rails/application/finisher.rb:132:in `block (2 levels) in <module:Finisher>'
from /usr/local/bundle/gems/activesupport-5.0.1/lib/active_support/callbacks.rb:396:in `instance_exec'
from /usr/local/bundle/gems/activesupport-5.0.1/lib/active_support/callbacks.rb:396:in `block in make_lambda'
from /usr/local/bundle/gems/activesupport-5.0.1/lib/active_support/callbacks.rb:169:in `call'
from /usr/local/bundle/gems/activesupport-5.0.1/lib/active_support/callbacks.rb:169:in `block (2 levels) in halting'
from /usr/local/bundle/gems/activesupport-5.0.1/lib/active_support/callbacks.rb:547:in `call'
from /usr/local/bundle/gems/activesupport-5.0.1/lib/active_support/callbacks.rb:547:in `block (2 levels) in default_terminator'
from /usr/local/bundle/gems/activesupport-5.0.1/lib/active_support/callbacks.rb:546:in `catch'
from /usr/local/bundle/gems/activesupport-5.0.1/lib/active_support/callbacks.rb:546:in `block in default_terminator'
from /usr/local/bundle/gems/activesupport-5.0.1/lib/active_support/callbacks.rb:170:in `call'
from /usr/local/bundle/gems/activesupport-5.0.1/lib/active_support/callbacks.rb:170:in `block in halting'
from /usr/local/bundle/gems/activesupport-5.0.1/lib/active_support/callbacks.rb:454:in `call'
from /usr/local/bundle/gems/activesupport-5.0.1/lib/active_support/callbacks.rb:454:in `block in call'
from /usr/local/bundle/gems/activesupport-5.0.1/lib/active_support/callbacks.rb:454:in `each'
from /usr/local/bundle/gems/activesupport-5.0.1/lib/active_support/callbacks.rb:454:in `call'
from /usr/local/bundle/gems/activesupport-5.0.1/lib/active_support/callbacks.rb:101:in `__run_callbacks__'
from /usr/local/bundle/gems/activesupport-5.0.1/lib/active_support/callbacks.rb:750:in `_run_run_callbacks'
from /usr/local/bundle/gems/activesupport-5.0.1/lib/active_support/callbacks.rb:90:in `run_callbacks'
from /usr/local/bundle/gems/activesupport-5.0.1/lib/active_support/execution_wrapper.rb:108:in `run!'
from /usr/local/bundle/gems/activesupport-5.0.1/lib/active_support/reloader.rb:113:in `run!'
from /usr/local/bundle/gems/activesupport-5.0.1/lib/active_support/reloader.rb:48:in `block (2 levels) in reload!'
from /usr/local/bundle/gems/activesupport-5.0.1/lib/active_support/reloader.rb:46:in `tap'
from /usr/local/bundle/gems/activesupport-5.0.1/lib/active_support/reloader.rb:46:in `block in reload!'
from /usr/local/bundle/gems/activesupport-5.0.1/lib/active_support/execution_wrapper.rb:85:in `wrap'
from /usr/local/bundle/gems/activesupport-5.0.1/lib/active_support/reloader.rb:45:in `reload!'
from /usr/local/bundle/gems/spring-1.7.2/lib/spring/application.rb:154:in `serve'
from /usr/local/bundle/gems/spring-1.7.2/lib/spring/application.rb:131:in `block in run'
from /usr/local/bundle/gems/spring-1.7.2/lib/spring/application.rb:125:in `loop'
from /usr/local/bundle/gems/spring-1.7.2/lib/spring/application.rb:125:in `run'
from /usr/local/bundle/gems/spring-1.7.2/lib/spring/application/boot.rb:19:in `<top (required)>'
from /usr/local/lib/ruby/site_ruby/2.2.0/rubygems/core_ext/kernel_require.rb:55:in `require'
from /usr/local/lib/ruby/site_ruby/2.2.0/rubygems/core_ext/kernel_require.rb:55:in `require'
from -e:1:in `<main>'
19:33:45 - ERROR - Failed: "BYEBUG=true spring rspec -color -f doc  -r /usr/local/bundle/gems/guard-rspec-4.7.3/lib/guard/rspec_formatter.rb -f Guard::RSpecFormatter --failure-exit-code 2  spec/controllers/api/buyside/ideas_controller_spec.rb" (exit code: 1)

If I run specs in a fresh container, this error does NOT occur until I save a file in the code that I COPY. After saving any file, I get the error when I try to run specs.

If I run the guard command without the spring tag, I also do not get the error, but of course I no longer have the benefit of spring preloading so performances is super slow.

Any idea what's going on? Was not having this problem before a recent upgrade to Rails 5. Happy to post other relevant information.

Thanks in advance.

Answer 1

This issue is discussed here: rails/spring#519

The workaround, as hinted in that issue, is to disable eager loading.

In config/environments/test.rb you change;

config.eager_load = true

to

config.eager_load = false