Ruby 3.1 extracts some gems to bundled one, which requires to add these gems to Gemfile explicitly.
`net/smtp` is one of them, which affected Action Mailbox bug report templates.
* Steps to reproduce
Install `ruby 3.1.0dev`
```
git clone https://github.com/rails/rails.git
cd rails/guides
ruby bug_report_templates/action_mailbox_gem.rb
ruby bug_report_templates/action_mailbox_main.rb
```
* This commit addresses the following error `cannot load such file -- net/smtp (LoadError)`
```
$ ruby bug_report_templates/action_mailbox_gem.rb
... snip ...
Using rails 6.1.0
/home/yahonda/.rbenv/versions/3.1.0-dev/lib/ruby/gems/3.1.0/gems/activesupport-6.1.0/lib/active_support/dependencies.rb:332:in `require': cannot load such file -- net/smtp (LoadError)
from /home/yahonda/.rbenv/versions/3.1.0-dev/lib/ruby/gems/3.1.0/gems/activesupport-6.1.0/lib/active_support/dependencies.rb:332:in `block in require'
from /home/yahonda/.rbenv/versions/3.1.0-dev/lib/ruby/gems/3.1.0/gems/activesupport-6.1.0/lib/active_support/dependencies.rb:299:in `load_dependency'
from /home/yahonda/.rbenv/versions/3.1.0-dev/lib/ruby/gems/3.1.0/gems/activesupport-6.1.0/lib/active_support/dependencies.rb:332:in `require'
from /home/yahonda/.rbenv/versions/3.1.0-dev/lib/ruby/gems/3.1.0/gems/mail-2.7.1/lib/mail.rb:9:in `<module:Mail>'
from /home/yahonda/.rbenv/versions/3.1.0-dev/lib/ruby/gems/3.1.0/gems/mail-2.7.1/lib/mail.rb:3:in `<top (required)>'
from /home/yahonda/.rbenv/versions/3.1.0-dev/lib/ruby/gems/3.1.0/gems/activesupport-6.1.0/lib/active_support/dependencies.rb:332:in `require'
from /home/yahonda/.rbenv/versions/3.1.0-dev/lib/ruby/gems/3.1.0/gems/activesupport-6.1.0/lib/active_support/dependencies.rb:332:in `block in require'
from /home/yahonda/.rbenv/versions/3.1.0-dev/lib/ruby/gems/3.1.0/gems/activesupport-6.1.0/lib/active_support/dependencies.rb:299:in `load_dependency'
from /home/yahonda/.rbenv/versions/3.1.0-dev/lib/ruby/gems/3.1.0/gems/activesupport-6.1.0/lib/active_support/dependencies.rb:332:in `require'
from /home/yahonda/.rbenv/versions/3.1.0-dev/lib/ruby/gems/3.1.0/gems/actionmailbox-6.1.0/lib/action_mailbox/mail_ext.rb:3:in `<top (required)>'
from /home/yahonda/.rbenv/versions/3.1.0-dev/lib/ruby/gems/3.1.0/gems/activesupport-6.1.0/lib/active_support/dependencies.rb:332:in `require'
from /home/yahonda/.rbenv/versions/3.1.0-dev/lib/ruby/gems/3.1.0/gems/activesupport-6.1.0/lib/active_support/dependencies.rb:332:in `block in require'
from /home/yahonda/.rbenv/versions/3.1.0-dev/lib/ruby/gems/3.1.0/gems/activesupport-6.1.0/lib/active_support/dependencies.rb:299:in `load_dependency'
from /home/yahonda/.rbenv/versions/3.1.0-dev/lib/ruby/gems/3.1.0/gems/activesupport-6.1.0/lib/active_support/dependencies.rb:332:in `require'
from /home/yahonda/.rbenv/versions/3.1.0-dev/lib/ruby/gems/3.1.0/gems/actionmailbox-6.1.0/lib/action_mailbox.rb:3:in `<top (required)>'
from /home/yahonda/.rbenv/versions/3.1.0-dev/lib/ruby/gems/3.1.0/gems/activesupport-6.1.0/lib/active_support/dependencies.rb:332:in `require'
from /home/yahonda/.rbenv/versions/3.1.0-dev/lib/ruby/gems/3.1.0/gems/activesupport-6.1.0/lib/active_support/dependencies.rb:332:in `block in require'
from /home/yahonda/.rbenv/versions/3.1.0-dev/lib/ruby/gems/3.1.0/gems/activesupport-6.1.0/lib/active_support/dependencies.rb:299:in `load_dependency'
from /home/yahonda/.rbenv/versions/3.1.0-dev/lib/ruby/gems/3.1.0/gems/activesupport-6.1.0/lib/active_support/dependencies.rb:332:in `require'
from /home/yahonda/.rbenv/versions/3.1.0-dev/lib/ruby/gems/3.1.0/gems/actionmailbox-6.1.0/lib/action_mailbox/engine.rb:9:in `<top (required)>'
from /home/yahonda/.rbenv/versions/3.1.0-dev/lib/ruby/gems/3.1.0/gems/activesupport-6.1.0/lib/active_support/dependencies.rb:332:in `require'
from /home/yahonda/.rbenv/versions/3.1.0-dev/lib/ruby/gems/3.1.0/gems/activesupport-6.1.0/lib/active_support/dependencies.rb:332:in `block in require'
from /home/yahonda/.rbenv/versions/3.1.0-dev/lib/ruby/gems/3.1.0/gems/activesupport-6.1.0/lib/active_support/dependencies.rb:299:in `load_dependency'
from /home/yahonda/.rbenv/versions/3.1.0-dev/lib/ruby/gems/3.1.0/gems/activesupport-6.1.0/lib/active_support/dependencies.rb:332:in `require'
from bug_report_templates/action_mailbox_gem.rb:17:in `<main>'
```
* Added comment when this dependency can be removed based on https://bugs.ruby-lang.org/issues/17873
Refer
https://github.com/ruby/ruby/pull/4530https://github.com/rails/rails/pull/42308
Co-authored-by: Jean Boussier <jean.boussier@gmail.com>