When a scope method name collides with a Kernel method, calling with #send on an ActiveRecord::Relation doesn't work

active_record_relation_send_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"
  # Activate the gem you are reporting the issue against.
  gem "activerecord", "5.1.0"
  gem "sqlite3"
end

require "active_record"
require "minitest/autorun"
require "logger"

# Ensure backward compatibility with Minitest 4
Minitest::Test = MiniTest::Unit::TestCase unless defined?(Minitest::Test)

# 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 :posts, force: true do |t|
  end

  create_table :comments, force: true do |t|
    t.integer :post_id
  end
end

class Post < ActiveRecord::Base
  has_many :comments

  # A scope whose name collides with Kernel, in this case Kernel#open
  def self.open
    "inside open"
  end
end

class Comment < ActiveRecord::Base
  belongs_to :post

  def self.open
    "inside open"
  end
end

class BugTest < Minitest::Test
  def test_association_stuff
    post = Post.create!
    post.comments << Comment.create!

    assert_equal 1, post.comments.count
    assert_equal 1, Comment.count
    assert_equal post.id, Comment.first.post.id
  end

  # When calling scopes dynamically with #send based on params values,
  # unexpected results are returned if the scope name collides with a Kernel method.
  # This test will fail with an ArgumentError because send bypasses #method_missing
  # on its way up the class heirarchy, and ActiveRecord relies on #method_missing to define
  # scopes on ActiveRecord::Relation descendant classes. The message ends up hitting
  # the Kernel implementation of #open.
  def test_send_with_kernel_method
    posts = Post.all
    params = { status: "open" }

    assert_equal "inside open", posts.send(params[:status])
  end

  # After calling the scope directly, thereby defining the method on
  # Comment::ActiveRecord_Relation with a call to #method_missing, using #send will work.
  def test_send_with_kernel_method_after_calling_it_directly
    comments = Comment.all
    params = { status: "open" }

    assert_equal "inside open", comments.open
    assert_equal "inside open", comments.send(params[:status])
  end
end