Reprodusable issue when eager loading relations from the same source

active_record_eager_loading_issue_from_same_source.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(true) do
  source "https://rubygems.org"
  gem "rails", github: "rails/rails"
  gem "sqlite3"
end

require "active_record"
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)

# Schema
ActiveRecord::Schema.define do
  ActiveRecord::Base.connection.create_table(:companies)

  ActiveRecord::Base.connection.create_table(:blogs) do |t|
    t.integer :company_id
  end

  ActiveRecord::Base.connection.create_table(:posts) do |t|
    t.integer :blog_id
    t.string :title
    t.boolean :promoted, default: false, null: false
  end
end

# Models
class Company < ActiveRecord::Base
  has_many :blogs

  has_many :posts, through: :blogs
  has_many :promoted_posts, -> { promoted }, through: :blogs, source: :posts
end

class Blog < ActiveRecord::Base
  belongs_to :company
  has_many :posts
end

class Post < ActiveRecord::Base
  belongs_to :blog

  scope :promoted, -> { where(promoted: true) }
end

class BugTest < Minitest::Test
  def test_eager_load_different_relations_with_same_source
    company       = Company.create!
    blog          = Blog.create!(company: company)
    post          = blog.posts.create!(title: "Regular Post", promoted: false)
    promoted_post = blog.posts.create!(title: "Promoted Post", promoted: true)

    company = Company.includes(:posts).includes(:promoted_posts).first
    assert_equal([promoted_post], company.promoted_posts.to_a, "Only a company's promoted posts should be returned")
  end
end