Add ActiveRecord::Relation support to CanCan can? check

ability.rb

require 'cancancan_ability_ext'

class Ability
  include CanCan::Ability
  include CanCanCanAbilityExt
  
  def initialize(user)
    can :clone, Post, { id: user.post_ids }
  end
end

cancancan_ability_ext.rb

# This module extends cancan abilities to work with ActiveRecord relations when used with +authorize!+ or
# +ability.can?+.
# 
# The extension is bypassed if attribute or extra_args are defined.
module CanCanCanAbilityExt
  def can?(action, subject, attribute = nil, *extra_args)
    if attribute.nil? && extra_args.blank?
      if subject.is_a?(ActiveRecord::Relation)
        return can_collection?(action, subject.klass, subject)
      end
    end

    super(action, subject, attribute, *extra_args)
  end

  private

  def can_collection?(action, klass, unchecked_records)
    accessible_records = klass.accessible_by(self, action).merge(unchecked_records)

    accessible_records.count == unchecked_records.count
  end
end

some_controller.rb

class PostsController < ApplicationController
  def index
    @posts = Post.accessible_by(current_ability)
  end
  
  def bulk_clone
    # We want to raise an AccessDenied instead of using accessible_by here because we would rather let the user
    # know they have an invalid post_id in their params than fulfilling the request on a subset of the post_ids.
    @posts = Post.find(params[:post_ids])
    authorize!(:clone, @posts)
  end
end