Ruby 3: LoadError: cannot load such file -- rexml/document

[dennyluan]

What Ruby, Rails and RSpec versions are you using?

Ruby version: 3.0.0
Rails version: 6.1.0
RSpec version: 3.10
MacOS big sur

Observed behaviour

On a fresh Rails 6.1 app with Ruby 3.0.0, rake spec fails to run any tests with the error:

» rake spec
/Users/dluan/.rbenv/versions/3.0.0/bin/ruby -I/Users/dluan/.rbenv/versions/3.0.0/lib/ruby/gems/3.0.0/gems/rspec-core-3.10.1/lib:/Users/dluan/.rbenv/versions/3.0.0/lib/ruby/gems/3.0.0/gems/rspec-support-3.10.1/lib /Users/dluan/.rbenv/versions/3.0.0/lib/ruby/gems/3.0.0/gems/rspec-core-3.10.1/exe/rspec --pattern spec/\*\*\{,/\*/\*\*\}/\*_spec.rb

An error occurred while loading ./spec/requests/cars_spec.rb. - Did you mean?
                    rspec ./spec/rails_helper.rb

Failure/Error: require File.expand_path('../config/environment', __dir__)

LoadError:
  cannot load such file -- rexml/document
# ./config/application.rb:7:in `<top (required)>'
# ./config/environment.rb:2:in `require_relative'
# ./config/environment.rb:2:in `<top (required)>'
# ./spec/rails_helper.rb:4:in `require'
# ./spec/rails_helper.rb:4:in `<top (required)>'
# ./spec/requests/cars_spec.rb:1:in `require'
# ./spec/requests/cars_spec.rb:1:in `<top (required)>'

I'm not sure if it's because I recently also upgraded my mac os to big sur, but for some reason this only breaks on fresh rails apps.

Likewise, running the test app below in Ruby 2.7.2 and 2.6.6 works just fine.

Expected behaviour

These tests pass on fresh rails 6.1 app with ruby 2.7.2.

Can you provide an example app?

rails new testapp
bundle add rspec-rails
rails generate rspec:install

Sample app here: https://github.com/dennyluan/rspec-ruby3-rails6

[JonRowe]

TL;DR; See rails/rails#40281 you probably need to add rexml to your gem file.

In Ruby 3, rexml stopped being a default Gem, the above PR was supposed to fix that for Rails, but it's not an RSpec issue because we don't have any dependency on it ourselves, its just sometimes needed by Rails and is supposed to be fixed upstream.

Hope this helps.

[dennyluan]

Thanks a lot Jon!