Demonstrating the anonymous modules when including blocks in scopes

Gemfile

# frozen_string_literal: true

source "https://rubygems.org"

gem "activerecord", github: "bodacious/rails"
gem "sqlite3"

main.rb

require "bundler"
Bundler.require

require "active_record"
ActiveRecord::Base.establish_connection({ adapter: "sqlite3", database: ":memory:" })

ActiveRecord::Base.connection.instance_eval do
  create_table(:products) do |t|
    t.string :name, limit: 50, null: false
    t.integer :price_cents, default: 0, null: false, limit: 10
  end
end

module FreeProductExtension
  def self.to_proc
    Proc.new { include FreeProductExtension }
  end
end

class ProductA < ActiveRecord::Base
  self.table_name = "products"

  scope :free, -> { where(price_cents: 0) }, &FreeProductExtension
end

class ProductB < ActiveRecord::Base
  self.table_name = "products"

  scope :free, -> { where(price_cents: 0) } do
    include FreeProductExtension
  end
end

class ProductC < ActiveRecord::Base
  self.table_name = "products"

  scope :free, -> { where(price_cents: 0) }, extend: FreeProductExtension
end

# Using the Module.to_proc approach...
ProductA.free.extensions
# => [#<Module:0x00000001129d25e8>]

# Using the scope(..., &block) approach...
ProductB.free.extensions
# => [#<Module:0x00000001129cab18>]

# Using the proposed `extend:` approach...
ProductC.free.extensions
# => [FreeProductExtension]