Relation#count should look for projections in chained relations and perform the count on the given column

Signed-off-by: Pratik Naik <pratiknaik@gmail.com>

activerecord/lib/active_record/relational_calculations.rb

@@ -109,11 +109,11 @@ module ActiveRecord
       # TODO : relation.projections only works when .select() was last in the chain. Fix it!
       case args.size
       when 0
-        select = @relation.send(:select_clauses).join(', ') if @relation.respond_to?(:projections) && @relation.projections.present?
+        select = get_projection_name_from_chained_relations
         column_name = select if select !~ /(,|\*)/
       when 1
         if args[0].is_a?(Hash)
-          select = @relation.send(:select_clauses).join(', ') if @relation.respond_to?(:projections) && @relation.projections.present?
+          select = get_projection_name_from_chained_relations
           column_name = select if select !~ /(,|\*)/
           options = args[0]
         else
@@ -165,5 +165,20 @@ module ActiveRecord
       column ? column.type_cast(value) : value
     end
 
+    def get_projection_name_from_chained_relations
+      name = nil
+      if @relation.respond_to?(:projections) && @relation.projections.present?
+        name = @relation.send(:select_clauses).join(', ')
+      elsif @relation.respond_to?(:relation) && relation = @relation.relation
+        while relation.respond_to?(:relation)
+          if relation.respond_to?(:projections) && relation.projections.present?
+            name = relation.send(:select_clauses).join(', ')
+          end
+          relation = relation.relation
+        end
+      end
+      name
+    end
+
   end
 end

activerecord/test/cases/relations_test.rb

@@ -376,7 +376,7 @@ class RelationTest < ActiveRecord::TestCase
     relations = []
     relations << (Post.order('comments.id DESC') & Post.eager_load(:last_comment) & Post.scoped)
     relations << (Post.eager_load(:last_comment) & Post.order('comments.id DESC') & Post.scoped)
-    
+
     relations.each do |posts|
       post = posts.find { |p| p.id == 1 }
       assert_equal Post.find(1).last_comment, post.last_comment
@@ -418,6 +418,9 @@ class RelationTest < ActiveRecord::TestCase
     Post.update_all(:comments_count => nil)
     posts = Post.scoped
 
+    assert_equal 0, posts.select('comments_count').where('id is not null').order('id').count
+    assert_equal 0, posts.where('id is not null').select('comments_count').count
+
     assert_equal 7, posts.select('comments_count').count('id')
     assert_equal 0, posts.select('comments_count').count
     assert_equal 0, posts.count(:comments_count)
@@ -435,4 +438,11 @@ class RelationTest < ActiveRecord::TestCase
     assert_no_queries { assert_equal 5, best_posts.size }
   end
 
+  def test_count_complex_chained_relations
+    posts = Post.select('comments_count').where('id is not null').group("author_id").where("comments_count > 0")
+
+    expected = { 1 => 2 }
+    assert_equal expected, posts.count
+  end
+
 end