uniq preserves order. References [4325].

git-svn-id: http://svn-commit.rubyonrails.org/rails/trunk@4326 5ecf4fe2-1ee6-0310-87b1-e25e094e27de

activerecord/lib/active_record/associations/association_collection.rb

@@ -109,7 +109,14 @@ module ActiveRecord
       end
 
       def uniq(collection = self)
-        collection.to_set.to_a
+        seen = Set.new
+        collection.inject([]) do |kept, record|
+          unless seen.include?(record.id)
+            kept << record
+            seen << record.id
+          end
+          kept
+        end
       end
 
       # Replace this collection with +other_array+

activerecord/test/associations_test.rb

@@ -1278,17 +1278,20 @@ class HasAndBelongsToManyAssociationsTest < Test::Unit::TestCase
   def test_habtm_saving_multiple_relationships
     new_project = Project.new("name" => "Grimetime")
     amount_of_developers = 4
-    developers = (0..amount_of_developers).collect {|i| Developer.create(:name => "JME #{i}") }
-  
+    developers = (0...amount_of_developers).collect {|i| Developer.create(:name => "JME #{i}") }.reverse
+
     new_project.developer_ids = [developers[0].id, developers[1].id]
     new_project.developers_with_callback_ids = [developers[2].id, developers[3].id]
     assert new_project.save
-    
+
     new_project.reload
     assert_equal amount_of_developers, new_project.developers.size
-    amount_of_developers.times do |i|
-      assert_equal developers[i].name, new_project.developers[i].name
-    end
+    assert_equal developers, new_project.developers
+  end
+
+  def test_habtm_unique_order_preserved
+    assert_equal [developers(:poor_jamis), developers(:jamis), developers(:david)], projects(:active_record).non_unique_developers
+    assert_equal [developers(:poor_jamis), developers(:jamis), developers(:david)], projects(:active_record).developers
   end
 
   def test_build

activerecord/test/fixtures/project.rb

@@ -1,5 +1,6 @@
 class Project < ActiveRecord::Base
-  has_and_belongs_to_many :developers, :uniq => true
+  has_and_belongs_to_many :developers, :uniq => true, :order => 'developers.name desc, developers.id desc'
+  has_and_belongs_to_many :non_unique_developers, :order => 'developers.name desc, developers.id desc', :class_name => 'Developer'
   has_and_belongs_to_many :limited_developers, :class_name => "Developer", :limit => 1
   has_and_belongs_to_many :developers_named_david, :class_name => "Developer", :conditions => "name = 'David'", :uniq => true
   has_and_belongs_to_many :salaried_developers, :class_name => "Developer", :conditions => "salary > 0"