CanCanCan Issue

main.rb

begin
  require "bundler/inline"
rescue LoadError => e
  $stderr.puts "Bundler version 1.10 or later is required. Please update your Bundler"
  raise e
end

gemfile do
  source "https://rubygems.org"
  gem "rails", "6.1.4.1"
  gem "cancancan"
  gem "sqlite3"
end

require "active_record"
require "cancancan"
require "cancan/model_adapters/conditions_extractor"
require "cancan/model_adapters/conditions_normalizer"
require "cancan/model_adapters/sti_normalizer"
require "cancan/model_adapters/active_record_adapter"
require "cancan/model_adapters/active_record_4_adapter"
require "cancan/model_adapters/active_record_5_adapter"
require "minitest/autorun"
require "logger"

# This connection will do for database-independent bug reports.
ActiveRecord::Base.establish_connection(adapter: "sqlite3", database: ":memory:")
ActiveRecord::Base.logger = Logger.new(STDOUT)

# create your tables here
ActiveRecord::Schema.define do
  create_table :customers, force: true  do |t|
    t.string :name
  end

  create_table :users, force: true  do |t|
    t.string :name
  end

  create_join_table :customers, :users, force: true
end

class Customer < ActiveRecord::Base
end

class User < ActiveRecord::Base
  has_and_belongs_to_many :customers
end

class Ability
  include CanCan::Ability

  class ViaIDs < Ability
    def initialize(user)
      can :manage, Customer, id: user.customer_ids
    end
  end

  class ViaSelect < Ability
    def initialize(user)
      can :manage, Customer, id: user.customers.select(:id)
    end
  end
end

class BugTest < Minitest::Test
  def setup
    @customers = ["UPS", "DHL", "FedEx"].map { |name|
      Customer.create! name: name
    }
    @other_customer = Customer.create! name: "Other"

    @user = User.create!(name: "manager").tap { |user|
      user.customers << @customers
    }
  end

  def test_via_ids
    verify_abilities Ability::ViaIDs.new(@user)
  end

  def test_via_select
    verify_abilities Ability::ViaSelect.new(@user)
  end

  private

  def verify_abilities(ability)
    customers = Customer.accessible_by(ability, :read).count
    assert_equal @customers.size, customers

    assert ability.can?(:read, @customers[0])
    assert ability.cannot?(:read, @other_customer)
  end
end