JRuby 9.0.0.0.pre2 raises "NameError: uninitialized class variable @@PREFIX_MAP in Object", doesn't occur in Ruby 2.2.x

[garysweaver]

Have a project with the following in the Gemfile:

gem 'rails-units', '~> 1.6.0', github: 'garysweaver/rails-units'

In Rails, when it hits Bundler.require(:default, Rails.env) in application.rb, it spews:

$ rake test
rake aborted!
NameError: uninitialized class variable @@PREFIX_MAP in Object
.../.rvm/gems/jruby-9.0.0.0.pre2@.../bundler/gems/rails-units-20913bc1b887/lib/rails_units/unit.rb:123:in `block in setup'
.../.rvm/gems/jruby-9.0.0.0.pre2@.../bundler/gems/rails-units-20913bc1b887/lib/rails_units/unit.rb:122:in `block in setup'
.../.rvm/gems/jruby-9.0.0.0.pre2@.../bundler/gems/rails-units-20913bc1b887/lib/rails_units/unit.rb:118:in `setup'
.../.rvm/gems/jruby-9.0.0.0.pre2@.../bundler/gems/rails-units-20913bc1b887/lib/rails_units/unit.rb:1272:in `<top>'
.../.rvm/gems/jruby-9.0.0.0.pre2@.../gems/activesupport-4.../lib/active_support/dependencies.rb:1:in `block in (root)'
.../.rvm/gems/jruby-9.0.0.0.pre2@.../gems/activesupport-4.../lib/active_support/dependencies.rb:229:in `require'
.../.rvm/gems/jruby-9.0.0.0.pre2@.../gems/activesupport-4.../lib/active_support/dependencies.rb:214:in `load_dependency'
.../.rvm/gems/jruby-9.0.0.0.pre2@.../gems/activesupport-4.../lib/active_support/dependencies.rb:229:in `<top>'
.../.rvm/gems/jruby-9.0.0.0.pre2@.../bundler/gems/rails-units-20913bc1b887/lib/rails-units.rb:12:in `block in (root)'
.../.rvm/gems/jruby-9.0.0.0.pre2@.../gems/bundler-1.10.3/lib/bundler/runtime.rb:1:in `block in (root)'
.../.rvm/gems/jruby-9.0.0.0.pre2@.../gems/bundler-1.10.3/lib/bundler/runtime.rb:76:in `require'
.../.rvm/gems/jruby-9.0.0.0.pre2@.../gems/bundler-1.10.3/lib/bundler/runtime.rb:72:in `require'
.../.rvm/gems/jruby-9.0.0.0.pre2@.../gems/bundler-1.10.3/lib/bundler/runtime.rb:61:in `<top>'
.../.rvm/gems/jruby-9.0.0.0.pre2@.../gems/bundler-1.10.3/lib/bundler.rb:134:in `<top>'
.../config/application.rb:10:in `(root)'
.../Rakefile:1:in `(root)'
.../Rakefile:5:in `block in (root)'

It doesn't raise this in Ruby 2.2.x or JRuby 1.7.20, so it's a bit odd.

[enebo]

Reduced test case:

class Foo
  @@A = {}

  def self.setup
    for name in [1] do
      for value in [1] do
        p @@A
      end
    end
  end
end

Foo.setup

Looks like we are counting for scopes in our calculation for cvars? Only one for loop is fine. for in Ruby is over time becoming increasingly esoteric so I suspect we lack some coverage here...

[subbuss]

@garysweaver please verify fix. Thanks.