fix to_sql output on eager loaded relations

2 files changed, 17 insertions, 1 deletions

diff --git a/activerecord/lib/active_record/relation.rb b/activerecord/lib/active_record/relation.rb
index 18fdac2600..612f376c55 100644
--- a/activerecord/lib/active_record/relation.rb
+++ b/activerecord/lib/active_record/relation.rb
@@ -501,7 +501,15 @@ module ActiveRecord
     #   User.where(name: 'Oscar').to_sql
     #   # => SELECT "users".* FROM "users"  WHERE "users"."name" = 'Oscar'
     def to_sql
-      @to_sql ||= klass.connection.to_sql(arel, bind_values.dup)
+      @to_sql ||= begin
+                    if eager_loading?
+                      join_dependency = construct_join_dependency
+                      relation = construct_relation_for_association_find(join_dependency)
+                      klass.connection.to_sql(relation.arel, relation.bind_values)
+                    else
+                      klass.connection.to_sql(arel, bind_values.dup)
+                    end
+                  end
     end
 
     # Returns a hash of where conditions.
diff --git a/activerecord/test/cases/relations_test.rb b/activerecord/test/cases/relations_test.rb
index 7a6d9be515..b205472cf5 100644
--- a/activerecord/test/cases/relations_test.rb
+++ b/activerecord/test/cases/relations_test.rb
@@ -481,6 +481,14 @@ class RelationTest < ActiveRecord::TestCase
     assert_equal Post.find(1).last_comment, post.last_comment
   end
 
+  def test_to_sql_on_eager_join
+    expected = assert_sql {
+      Post.eager_load(:last_comment).order('comments.id DESC').to_a
+    }.first
+    actual = Post.eager_load(:last_comment).order('comments.id DESC').to_sql
+    assert_equal expected, actual
+  end
+
   def test_loading_with_one_association_with_non_preload
     posts = Post.eager_load(:last_comment).order('comments.id DESC')
     post = posts.find { |p| p.id == 1 }