Delegate StubConnection#pubsub and StubConnection#config to ActionCable.server

[julianfssen]

Motivation / Background

Previously, ActionCable::Channel::ConnectionStub would throw a NoMethodError when the channel under test calls stop_stream_from, as shown in the test case below:

# frozen_string_literal: true

require "bundler/inline"

gemfile(true) do
  source "https://rubygems.org"

  git_source(:github) { |repo| "https://github.com/#{repo}.git" }

  # Activate the gem you are reporting the issue against.
  gem "actioncable", "~> 7.0.0"
end

require "minitest/autorun"
require "action_cable"

ActionCable.server.config.cable = { "adapter" => "test" }

class ChatChannel < ActionCable::Channel::Base
  def subscribed
    stream_from "test"
  end 

  def unsubscribed
    stop_stream_from "test"
  end 
end

class ChatChannelTest < ActionCable::Channel::TestCase
  test "unsubscribe" do
    stub_connection

    subscribe
    unsubscribe # raises a NoMethodError

    assert_no_streams
  end 
end

This happens because stop_stream_from calls pubsub when unsubscribing from a channel, which is missing from the ConnectionStub implementation.

Detail

This PR fixes this issue by assigning the ActionCable.server singleton to a @server instance variable in
ActionCable::Channel::ConnectionStub.

This lets us delegate the config and pubsub method calls to it, hence fixing the NoMethodError issue.

I updated config to be delegated to @server as well since config defaults to ActionCable::Server::Configuration.new.

We do something similar in ActionCable::TestHelper#pubsub_adapter as well:

rails/actioncable/lib/action_cable/test_helper.rb

Lines 133 to 135 in 13cff7e

	def pubsub_adapter # :nodoc:
	ActionCable.server.pubsub
	end

Additional information

I'm not sure if I should add a changelog entry for this. But, I added it anyway since I feel adding@server = ActionCable.server qualifies as a behavior change.

Checklist

Before submitting the PR make sure the following are checked:

• This Pull Request is related to one change. Changes that are unrelated should be opened in separate PRs.
• Commit message has a detailed description of what changed and why. If this PR fixes a related issue include it in the commit message. Ex: [Fix #issue-number]
• Tests are added or updated if you fix a bug or add a feature.
• CHANGELOG files are updated for the changed libraries if there is a behavior change or additional feature. Minor bug fixes and documentation changes should not be included.

[julianfssen]

Good morning, @byroot !

I saw you were involved with merging the last few ActionCable-related PRs to main. I was wondering if you'd have the time to review this PR?

It involves a test-related issue so it's not a big issue and I understand if it's not crucial to merge in for now. Thank you!

[byroot]

LGTM.

[julianfssen]

LGTM.

Awesome! Thank you, @byroot 🙌