Weird `require 'enumerator'` issue caused by this gem

[fbacall]

Hi,

I'm in the process of upgrading our Rails app to version 6 on Ruby 2.7.5, and have encountered a weird interaction between three gems: this one, bio ruby and ruby-progressbar.

It seems that when having ruby-progressbar loaded when this gem is loaded, something breaks that then causes require 'enumerator' (used in bioruby) to cause:

`require': cannot load such file -- enumerator (LoadError)

It seems to happen because ruby-progressbar includes a file named enumerator.rb.

I've created a minimal repository that reproduces this error: https://github.com/fbacall/rdf-issue

[gkellogg]

Ruby RDF also has an enumerator class, but loading should honor module pathing. What makes you suspect that the issue is in rdf and not one of the other gems?

[fbacall]

I tried various combinations of the affected gems, and each one individually.

In my repo above I don't use any gems except linkeddata, and a very basic require of an enumerator.rb file under a sub path/namespace.

Admittedly I can't see where the problem is in rdf-ruby.

It seems something to do with these autoload statements: https://github.com/ruby-rdf/rdf/blob/develop/lib/rdf/mixin/queryable.rb#L12

If I hack the gem source locally and rename rdf/mixin/enumerator.rb to enumerator2.rb (and update the autoloads) the problem goes away. Perhaps this is a Ruby bug?

[gkellogg]

Autoload is fairly mysterious. I can probably replace Enumerator to be a require_local instead of an autoload, but I won’t be able to get to it until next week at the earliest. You might try cloning GitHub.com/Ruby-rdf/rdf and make the change yourself to see if that addresses the issue properly.

[gkellogg]

@fbacall I'm still not sure what made the internal Enumerator class and file special, but I folded it in to their respective mixins and your test seems to work properly now. Let me know if this does, indeed, fix the problem, and I'll push a new release out shortly.

[fbacall]

Thanks! Those changes seem to fix everything (feel free to close this)

I spent a while trying to figure out the problem myself but didn't really get anywhere. I did narrow it down to something that changed between rdf-n3 version 3.1.1 (working) and 3.1.2 (broken), at least in my example repo. It's also something to do with the Ruby version. rdf-n3 3.1.2 works fine on Ruby 2.6, just not on 2.7.

During my debugging I found that the behaviour of resolve_feature_path seems to have changed between Ruby 2.6 and 2.7:

2.6.6 :001 > RubyVM.resolve_feature_path('enumerator')
 => [:so, false] 

2.7.5 :001 > $LOAD_PATH.resolve_feature_path('enumerator')
Traceback (most recent call last):
 `<main>'                     
        21: from /home/finn/.rvm/gems/ruby-2.7.5/bin/ruby_executable_hooks:22:in `eval'                       
        20: from /home/finn/.rvm/gems/ruby-2.7.5/bin/irb:23:in `<main>'
        19: from /home/finn/.rvm/gems/ruby-2.7.5/bin/irb:23:in `load'
        18: from /home/finn/.rvm/gems/ruby-2.7.5/gems/irb-1.4.1/exe/irb:11:in `<top (required)>'              
         1: from (irb):1:in `<main>'
(irb):1:in `resolve_feature_path': cannot load such file -- enumerator (LoadError)     

which perhaps hints at something internal to Ruby that is causing this issue. I couldn't find any documentation that suggests this change is intentional. Not sure if that helps at all.