A Reproduction Script for Rails issue #41811

41811.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", "5.2.4.5"
  gem 'sqlite3'
end

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

ActiveRecord::Base.establish_connection(adapter: "sqlite3", database: ":memory:")
ActiveRecord::Base.logger = Logger.new(STDOUT)

ActiveRecord::Schema.define do
  create_table :posts do |t|
    t.string :title
  end

  create_table :comments do |t|
    t.integer :post_id
    t.string :body
  end
end

class Post < ActiveRecord::Base
  has_many :comments, inverse_of: :post
  accepts_nested_attributes_for :comments

  validates :title, presence: true
end

class Comment < ActiveRecord::Base
  belongs_to :post, inverse_of: :comments
  accepts_nested_attributes_for :post
  
  validates :body, presence: true
end

class BugTest < Minitest::Test
  # currently fails
  def test_invalid_attributes
    post = Post.new(title: 'foo', comments_attributes: [{body: 'bar'}, {body: nil}, {body: 'baz'}])
    
    refute post.valid?
    refute post.errors.empty?
  end
  
  # currently passes
  def test_invalid_attributes_end_of_list
    post = Post.new(title: 'foo', comments_attributes: [{body: 'bar'}, {body: 'baz'}, {body: nil}])
    
    refute post.valid?
    refute post.errors.empty?
  end
  
  # currently passes
  def test_invalid_attributes_one_attribute
    post = Post.new(title: 'foo', comments_attributes: [{body: nil}])
    
    refute post.valid?
    refute post.errors.empty?
  end
end