ActiveModel support for the :include serialization option

This commit moves support for the :include serialization option for
serializing associated objects out of ActiveRecord in into ActiveModel.
The following methods support the :include option:

  * serializable_hash
  * to_json
  * to_xml

Instances must respond to methods named by the values of the :includes
array (or keys of the :includes hash). If an association method returns
an object that is_a?(Enumerable) (which AR has_many associations do), it
is assumed to be a collection association, and its elements must respond
to :serializable_hash. Otherwise it must respond to :serializable_hash
itself.

While here, fix #858, XmlSerializer should not singularize already
singular association names.

2 files changed, 117 insertions, 8 deletions

diff --git a/activemodel/test/cases/serialization_test.rb b/activemodel/test/cases/serialization_test.rb
index 10cb600e7b..5122f08eec 100644
--- a/activemodel/test/cases/serialization_test.rb
+++ b/activemodel/test/cases/serialization_test.rb
@@ -1,13 +1,19 @@
 require "cases/helper"
+require 'active_support/core_ext/object/instance_variables'
 
 class SerializationTest < ActiveModel::TestCase
   class User
     include ActiveModel::Serialization
 
-    attr_accessor :name, :email, :gender
+    attr_accessor :name, :email, :gender, :address, :friends
+
+    def initialize(name, email, gender)
+      @name, @email, @gender = name, email, gender
+      @friends = []
+    end
 
     def attributes
-      @attributes ||= {'name' => 'nil', 'email' => 'nil', 'gender' => 'nil'}
+      instance_values.except("address", "friends")
     end
 
     def foo
@@ -15,11 +21,25 @@ class SerializationTest < ActiveModel::TestCase
     end
   end
 
+  class Address
+    include ActiveModel::Serialization
+
+    attr_accessor :street, :city, :state, :zip
+
+    def attributes
+      instance_values
+    end
+  end
+
   setup do
-    @user = User.new
-    @user.name = 'David'
-    @user.email = 'david@example.com'
-    @user.gender = 'male'
+    @user = User.new('David', 'david@example.com', 'male')
+    @user.address = Address.new
+    @user.address.street = "123 Lane"
+    @user.address.city = "Springfield"
+    @user.address.state = "CA"
+    @user.address.zip = 11111
+    @user.friends = [User.new('Joe', 'joe@example.com', 'male'),
+                     User.new('Sue', 'sue@example.com', 'female')]
   end
 
   def test_method_serializable_hash_should_work
@@ -57,4 +77,45 @@ class SerializationTest < ActiveModel::TestCase
     assert_equal expected , @user.serializable_hash(:methods => [:bar])
   end
 
+  def test_include_option_with_singular_association
+    expected =  {"name"=>"David", "gender"=>"male", "email"=>"david@example.com",
+                 :address=>{"street"=>"123 Lane", "city"=>"Springfield", "state"=>"CA", "zip"=>11111}}
+    assert_equal expected , @user.serializable_hash(:include => :address)
+  end
+
+  def test_include_option_with_plural_association
+    expected =  {"email"=>"david@example.com", "gender"=>"male", "name"=>"David",
+                 :friends=>[{"name"=>'Joe', "email"=>'joe@example.com', "gender"=>'male'},
+                            {"name"=>'Sue', "email"=>'sue@example.com', "gender"=>'female'}]}
+    assert_equal expected , @user.serializable_hash(:include => :friends)
+  end
+
+  def test_include_option_with_empty_association
+    @user.friends = []
+    expected =  {"email"=>"david@example.com", "gender"=>"male", "name"=>"David", :friends=>[]}
+    assert_equal expected , @user.serializable_hash(:include => :friends)
+  end
+
+  def test_multiple_includes
+    expected =  {"email"=>"david@example.com", "gender"=>"male", "name"=>"David",
+                 :address=>{"street"=>"123 Lane", "city"=>"Springfield", "state"=>"CA", "zip"=>11111},
+                 :friends=>[{"name"=>'Joe', "email"=>'joe@example.com', "gender"=>'male'},
+                            {"name"=>'Sue', "email"=>'sue@example.com', "gender"=>'female'}]}
+    assert_equal expected , @user.serializable_hash(:include => [:address, :friends])
+  end
+
+  def test_include_with_options
+    expected =  {"email"=>"david@example.com", "gender"=>"male", "name"=>"David",
+                 :address=>{"street"=>"123 Lane"}}
+    assert_equal expected , @user.serializable_hash(:include => {:address => {:only => "street"}})
+  end
+
+  def test_nested_include
+    @user.friends.first.friends = [@user]
+    expected =  {"email"=>"david@example.com", "gender"=>"male", "name"=>"David",
+                 :friends=>[{"name"=>'Joe', "email"=>'joe@example.com', "gender"=>'male',
+                             :friends => ["email"=>"david@example.com", "gender"=>"male", "name"=>"David"]},
+                            {"name"=>'Sue', "email"=>'sue@example.com', "gender"=>'female', :friends => []}]}
+    assert_equal expected , @user.serializable_hash(:include => {:friends => {:include => :friends}})
+  end
 end
diff --git a/activemodel/test/cases/serializers/xml_serialization_test.rb b/activemodel/test/cases/serializers/xml_serialization_test.rb
index f978191d22..a38ef8e223 100644
--- a/activemodel/test/cases/serializers/xml_serialization_test.rb
+++ b/activemodel/test/cases/serializers/xml_serialization_test.rb
@@ -7,9 +7,11 @@ class Contact
   extend ActiveModel::Naming
   include ActiveModel::Serializers::Xml
 
+  attr_accessor :address, :friends
+
   def attributes
-    instance_values
-  end unless method_defined?(:attributes)
+    instance_values.except("address", "friends")
+  end
 end
 
 module Admin
@@ -20,6 +22,17 @@ end
 class Customer < Struct.new(:name)
 end
 
+class Address
+  extend ActiveModel::Naming
+  include ActiveModel::Serializers::Xml
+
+  attr_accessor :street, :city, :state, :zip
+
+  def attributes
+    instance_values
+  end
+end
+
 class XmlSerializationTest < ActiveModel::TestCase
   def setup
     @contact = Contact.new
@@ -30,6 +43,12 @@ class XmlSerializationTest < ActiveModel::TestCase
     customer = Customer.new
     customer.name = "John"
     @contact.preferences = customer
+    @contact.address = Address.new
+    @contact.address.street = "123 Lane"
+    @contact.address.city = "Springfield"
+    @contact.address.state = "CA"
+    @contact.address.zip = 11111
+    @contact.friends = [Contact.new, Contact.new]
   end
 
   test "should serialize default root" do
@@ -138,4 +157,33 @@ class XmlSerializationTest < ActiveModel::TestCase
     assert_match %r{<contact type="Contact">}, xml
     assert_match %r{<name>aaron stack</name>}, xml
   end
+
+  test "include option with singular association" do
+    xml = @contact.to_xml :include => :address, :indent => 0
+    assert xml.include?(@contact.address.to_xml(:indent => 0, :skip_instruct => true))
+  end
+
+  test "include option with plural association" do
+    xml = @contact.to_xml :include => :friends, :indent => 0
+    assert_match %r{<friends type="array">}, xml
+    assert_match %r{<friend type="Contact">}, xml
+  end
+
+  test "multiple includes" do
+    xml = @contact.to_xml :indent => 0, :skip_instruct => true, :include => [ :address, :friends ]
+    assert xml.include?(@contact.address.to_xml(:indent => 0, :skip_instruct => true))
+    assert_match %r{<friends type="array">}, xml
+    assert_match %r{<friend type="Contact">}, xml
+  end
+
+  test "include with options" do
+    xml = @contact.to_xml :indent  => 0, :skip_instruct => true, :include => { :address => { :only => :city } }
+    assert xml.include?(%(><address><city>Springfield</city></address>))
+  end
+
+  test "propagates skip_types option to included associations" do
+    xml = @contact.to_xml :include => :friends, :indent => 0, :skip_types => true
+    assert_match %r{<friends>}, xml
+    assert_match %r{<friend>}, xml
+  end
 end