add tests for readme example

README.md

@@ -64,31 +64,30 @@ class Book < ActiveRecord::Base
 
  # foreword writers for the book via a join table
  has_many :forewords
- has_many :foreword_writers, through: :forewords, source: :user
+ has_many :prefacers, through: :forewords, source: :user
 
  # union association for all contributors to the book
- has_many :contributors, union_of: %i[
+ has_many :contributors, class_name: 'User', union_of: %i[
  author
  coauthors
  editors
  illustrators
- foreword_writers
+ prefacers
  ]
 end
-
 ```
 
 Here's a quick example of what's possible:
 
 ```ruby
 # contributors to the book
-primary_author = User.create(name: 'Isaac Asimov')
+author = User.create(name: 'Isaac Asimov')
 editor = User.create(name: 'John W. Campbell')
 illustrator = User.create(name: 'Frank Kelly Freas')
 writer = User.create(name: 'Ray Bradbury')
 
 # create book by the author
-book = Book.create(title: 'I, Robot', primary_author:)
+book = Book.create(title: 'I, Robot', author:)
 
 # assign an editor
 Edit.create(user: editor, book:)
@@ -99,7 +98,7 @@ Illustration.create(user: illustrator, book:)
 # assign a foreword writer
 Foreword.create(user: writer, book:)
 
-# access all contributors (primary author, editor, illustrator, foreword writer)
+# access all contributors (author, editor, illustrator, etc.)
 book.contributors.to_a
 # => [#<User id=1, name="Isaac Asimov">, #<User id=2, name="John W. Campbell">, #<User id=3, name="Frank Kelly Freas">, #<User id=4, name="Ray Bradbury">]
 

spec/union_of_spec.rb

@@ -1309,4 +1309,198 @@ def owned = where(owner: proxy_association.owner)
 
  # TODO(ezekg) Add exhaustive tests for all association macros, e.g.
  # belongs_to, has_many, etc.
+
+ describe 'README' do
+ temporary_table :users, force: true do |t|
+ t.string :name
+ end
+
+ temporary_table :books do |t|
+ t.integer :author_id
+ t.string :title
+ end
+
+ temporary_table :coauthorships do |t|
+ t.integer :book_id
+ t.integer :user_id
+ end
+
+ temporary_table :edits do |t|
+ t.integer :book_id
+ t.integer :user_id
+ end
+
+ temporary_table :illustrations do |t|
+ t.integer :book_id
+ t.integer :user_id
+ end
+
+ temporary_table :forewords do |t|
+ t.integer :book_id
+ t.integer :user_id
+ end
+
+ temporary_model :user do
+ has_many :books
+ has_many :coauthorships
+ has_many :edits
+ has_many :illustrations
+ has_many :forewords
+ end
+
+ temporary_model :coauthorship do
+ belongs_to :book
+ belongs_to :user
+ end
+
+ temporary_model :edit do
+ belongs_to :book
+ belongs_to :user
+ end
+
+ temporary_model :illustration do
+ belongs_to :book
+ belongs_to :user
+ end
+
+ temporary_model :foreword do
+ belongs_to :book
+ belongs_to :user
+ end
+
+ temporary_model :book do
+ # the primary author of the book
+ belongs_to :author, class_name: 'User', foreign_key: 'author_id', optional: true
+
+ # coauthors of the book via a join table
+ has_many :coauthorships
+ has_many :coauthors, through: :coauthorships, source: :user
+
+ # editors for the book via a join table
+ has_many :edits
+ has_many :editors, through: :edits, source: :user
+
+ # illustrators for the book via a join table
+ has_many :illustrations
+ has_many :illustrators, through: :illustrations, source: :user
+
+ # foreword writers for the book via a join table
+ has_many :forewords
+ has_many :prefacers, through: :forewords, source: :user
+
+ # union association for all contributors to the book
+ has_many :contributors, class_name: 'User', union_of: %i[
+ author
+ coauthors
+ editors
+ illustrators
+ prefacers
+ ]
+ end
+
+ let(:author) { User.create(name: 'Isaac Asimov') }
+ let(:editor) { User.create(name: 'John W. Campbell') }
+ let(:illustrator) { User.create(name: 'Frank Kelly Freas') }
+ let(:writer) { User.create(name: 'Ray Bradbury') }
+ let(:book) {
+ book = Book.create(title: 'I, Robot', author:)
+
+ Edit.create(user: editor, book:)
+ Illustration.create(user: illustrator, book:)
+ Foreword.create(user: writer, book:)
+
+ book
+ }
+
+ it 'should return contributors' do
+ expect(book.contributors).to satisfy { _1.to_a in [author, editor, illustrator, writer] }
+ end
+
+ it 'should use limit' do
+ expect(book.contributors.order(:name).limit(3)).to satisfy { _1.to_a in [author, editor, illustrator] }
+ end
+
+ it 'should use predicate' do
+ expect(book.contributors.where(id: editor.id)).to satisfy { _1.to_a in [editor] }
+ end
+
+ it 'should use UNION' do
+ expect(book.contributors.to_sql).to match_sql <<~SQL.squish
+ SELECT
+ users.*
+ FROM
+ users
+ WHERE
+ users.id IN (
+ SELECT
+ users.id
+ FROM
+ (
+ (
+ SELECT
+ users.id
+ FROM
+ users
+ WHERE
+ users.id = 1
+ LIMIT
+ 1
+ )
+ UNION
+ (
+ SELECT
+ users.id
+ FROM
+ users INNER JOIN coauthorships ON users.id = coauthorships.user_id
+ WHERE
+ coauthorships.book_id = 1
+ )
+ UNION
+ (
+ SELECT
+ users.id
+ FROM
+ users INNER JOIN edits ON users.id = edits.user_id
+ WHERE
+ edits.book_id = 1
+ )
+ UNION
+ (
+ SELECT
+ users.id
+ FROM
+ users INNER JOIN illustrations ON users.id = illustrations.user_id
+ WHERE
+ illustrations.book_id = 1
+ )
+ UNION
+ (
+ SELECT
+ users.id
+ FROM
+ users INNER JOIN forewords ON users.id = forewords.user_id
+ WHERE
+ forewords.book_id = 1
+ )
+ ) users
+ )
+ SQL
+ end
+
+ it 'should support joins' do
+ expect { Book.joins(:contributors).where(contributors: { user_id: author.id }) }.to_not raise_error
+ end
+
+ it 'should support preloading' do
+ expect { Book.preload(:contributors) }.to_not raise_error
+ end
+
+ it 'should support eager loading' do
+ expect { Book.eager_load(:contributors) }.to_not raise_error
+ end
+
+ it 'should support includes' do
+ expect { Book.includes(:contributors) }.to_not raise_error
+ end
+ end
 end