Production rails server does not boot if skipping action cable in Rails 8.0.0.alpha

[jeromedalbert]

Steps to reproduce

rails new myapp --main --skip-action-cable
RAILS_ENV=production rails server

or

rails new myapp --main --skip-action-cable
sed -i -e 's/eager_load = false/eager_load = true/' config/environments/development.rb
rails server

Expected behavior

Server boots.

Actual behavior

Server does not boot and errors out:

=> Booting Puma
=> Rails 8.0.0.alpha application starting in development
=> Run `bin/rails server --help` for more startup options
Exiting
/Users/jerome/.asdf/installs/ruby/3.3.1/lib/ruby/gems/3.3.0/gems/turbo-rails-2.0.5/app/channels/turbo/streams_channel.rb:34:in `<main>': uninitialized constant ActionCable (NameError)

class Turbo::StreamsChannel < ActionCable::Channel::Base
                              ^^^^^^^^^^^

System configuration

Rails version: 8.0.0.alpha

Ruby version: 3.3.1

Additional information

Rails 8 has the Turbo gem included by default. But Turbo Streams depends on Action Cable. When using --skip-action-cable, the line require "action_cable/engine" is commented out in config/application.rb, which makes Turbo error out. A current workaround is to uncomment that line manually.

Some ideas for a solution:

1. I am not familiar with Turbo, but maybe edit the gem to disable Turbo Streams if Action Cable is not defined
2. Exclude turbo-rails when --skip-action-cable is supplied (suggested by @dbelling in #51768)
3. Ignore --skip-action-cable unless a new --skip-turbo option is supplied (to be implemented, this option does not currently exist)
4. Remove the --skip-action-cable option altogether, which seems too drastic
5. Any other idea

[justinko]

I vote for 3, but instead of ignoring, raise an error stating turbo must be skipped as well.

[zzak]

We do not need two issues for the same bug, thank you for reporting.