Merge pull request #22486 from methyl/fix-includes-for-groupped-association

Pass group values when including association

Conflicts:
	activerecord/CHANGELOG.md

3 files changed, 26 insertions, 1 deletions

diff --git a/activerecord/CHANGELOG.md b/activerecord/CHANGELOG.md
index 9819b85205..08f170f7d2 100644
--- a/activerecord/CHANGELOG.md
+++ b/activerecord/CHANGELOG.md
@@ -1,3 +1,7 @@
+*   Use group by values when preloading scoped associations.
+
+    *Lucjan Suski*
+
 ## Rails 5.0.0.beta1 (December 18, 2015) ##
 
 *   No changes.
diff --git a/activerecord/lib/active_record/associations/preloader/association.rb b/activerecord/lib/active_record/associations/preloader/association.rb
index e11a5cfb8a..91e7f90739 100644
--- a/activerecord/lib/active_record/associations/preloader/association.rb
+++ b/activerecord/lib/active_record/associations/preloader/association.rb
@@ -107,7 +107,7 @@ module ActiveRecord
           @preloaded_records = slices.flat_map do |slice|
             records_for(slice)
           end
-          @preloaded_records.group_by do |record| 
+          @preloaded_records.group_by do |record|
             convert_key(record[association_key_name])
           end
         end
@@ -139,6 +139,10 @@ module ActiveRecord
             scope.order!(order_values)
           end
 
+          if group_values = preload_values[:group] || values[:group]
+            scope.group!(group_values)
+          end
+
           if preload_values[:reordering] || values[:reordering]
             scope.reordering_value = true
           end
diff --git a/activerecord/test/cases/associations/eager_test.rb b/activerecord/test/cases/associations/eager_test.rb
index 874d53c51f..966789884b 100644
--- a/activerecord/test/cases/associations/eager_test.rb
+++ b/activerecord/test/cases/associations/eager_test.rb
@@ -1242,6 +1242,23 @@ class EagerAssociationTest < ActiveRecord::TestCase
     assert_equal projects.last.mentor.developers.first.contracts, projects.last.developers.last.contracts
   end
 
+  def test_eager_load_with_group_clause
+    assert_nothing_raised(ActiveRecord::StatementInvalid) do
+      subclass = Class.new(ActiveRecord::Base) do
+        def self.name; "Author"; end
+        self.table_name = "authors"
+        has_many :posts_ordered_by_comments_tags_count, -> {
+          joins('LEFT JOIN comments ON comments.post_id = posts.id').
+          order("SUM(comments.tags_count)").
+          group('posts.id') }, class_name: "Post"
+      end
+
+      preloaded = subclass.includes(:posts_ordered_by_comments_tags_count).map(&:posts_ordered_by_comments_tags_count)
+      loaded = subclass.all.map(&:posts_ordered_by_comments_tags_count)
+      assert preloaded == loaded, 'Preloaded records differ from expected result.'
+    end
+  end
+
   test "scoping with a circular preload" do
     assert_equal Comment.find(1), Comment.preload(:post => :comments).scoping { Comment.find(1) }
   end