Eager loading an association should not change the count of children

[#4971 state:resolved]

Signed-off-by: José Valim <jose.valim@gmail.com>

activerecord/lib/active_record/associations.rb

@@ -1815,6 +1815,10 @@ module ActiveRecord
               when Hash
                 associations.keys.each do |name|
                   reflection = base.reflections[name]
+                  
+                  if records.any? && reflection.options && reflection.options[:uniq]
+                    records.each { |record| record.send(reflection.name).target.uniq! }
+                  end
 
                   parent_records = []
                   records.each do |record|

activerecord/test/cases/associations_test.rb

@@ -14,11 +14,24 @@ require 'models/reader'
 require 'models/parrot'
 require 'models/ship_part'
 require 'models/ship'
+require 'models/liquid'
+require 'models/molecule'
+require 'models/electron'
 
 class AssociationsTest < ActiveRecord::TestCase
   fixtures :accounts, :companies, :developers, :projects, :developers_projects,
            :computers, :people, :readers
 
+  def test_eager_loading_should_not_change_count_of_children
+    liquid = Liquid.create(:name => 'salty')
+    molecule = liquid.molecules.create(:name => 'molecule_1')
+    molecule.electrons.create(:name => 'electron_1')
+    molecule.electrons.create(:name => 'electron_2')
+
+    liquids = Liquid.includes(:molecules => :electrons).where('molecules.id is not null')
+    assert_equal 1, liquids[0].molecules.length
+  end
+
   def test_loading_the_association_target_should_keep_child_records_marked_for_destruction
     ship = Ship.create!(:name => "The good ship Dollypop")
     part = ship.parts.create!(:name => "Mast")

activerecord/test/models/electron.rb

@@ -0,0 +1,3 @@
+class Electron < ActiveRecord::Base
+  belongs_to :molecule
+end

activerecord/test/models/liquid.rb

@@ -0,0 +1,5 @@
+class Liquid < ActiveRecord::Base
+  set_table_name :liquid
+  has_many :molecules, :uniq => true
+end
+

activerecord/test/models/molecule.rb

@@ -0,0 +1,4 @@
+class Molecule < ActiveRecord::Base
+  belongs_to :liquid
+  has_many :electrons
+end

activerecord/test/schema/schema.rb

@@ -618,6 +618,19 @@ ActiveRecord::Schema.define do
     t.datetime :updated_at
   end
 
+  create_table :liquid, :force => true do |t|
+    t.string :name
+  end
+  create_table :molecules, :force => true do |t|
+    t.integer :liquid_id
+    t.string :name
+  end
+  create_table :electrons, :force => true do |t|
+    t.integer :molecule_id
+    t.string :name
+  end
+
+
   except 'SQLite' do
     # fk_test_has_fk should be before fk_test_has_pk
     create_table :fk_test_has_fk, :force => true do |t|