Eager loading with conditions not working as expected, both with `#where` and with `#joins`

eager_load_with_conditions_bug.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)

ActiveRecord::Schema.define do
  create_table :parents, force: true  do |t|
  end

  create_table :kiddos, force: true  do |t|
    t.integer :parent_id
    t.string  :gender
  end
end

class Parent < ActiveRecord::Base
  has_many :kiddos
end

class Kiddo < ActiveRecord::Base
  belongs_to :parent
end

class BugTest < Minitest::Test
  def setup
    parent = Parent.create!
    parent.kiddos << Kiddo.create!(gender: "M")
    parent.kiddos << Kiddo.create!(gender: "F")
    parent.kiddos << Kiddo.create!(gender: "MF")
  end

  def teardown
    Parent.destroy_all
    Kiddo.destroy_all
  end

  def test_eager_load_with_conditions_where
    query_result = Parent.includes(:kiddos).where(kiddos: { gender: ["F", "MF"] }).first

    assert query_result.kiddos.all? { |kiddo| kiddo.gender.include?("F") }, "should only return kiddos whose gender includes 'F'"
    assert query_result.kiddos.none? { |kiddo| kiddo.gender == "M" }, "should not return any kiddos with gender of 'M'"
    assert_equal 2, query_result.kiddos.count
  end

  def test_eager_load_with_conditions_joins
    query_result = Parent.includes(:kiddos).joins(:kiddos).where(kiddos: { gender: ["F", "MF"] }).first

    assert query_result.kiddos.all? { |kiddo| kiddo.gender.include?("F") }, "should only return kiddos whose gender includes 'F'"
    assert query_result.kiddos.none? { |kiddo| kiddo.gender == "M" }, "should not return any kiddos with gender of 'M'"
    assert_equal 2, query_result.kiddos.count
  end
end