Fix preload with nested associations

When the middle association doesn't have any records and the inner
association is not an empty scope the owner will be `nil` so we can't
try to reset the inverse association.

2 files changed, 11 insertions, 0 deletions

diff --git a/activerecord/test/cases/associations/has_many_through_associations_test.rb b/activerecord/test/cases/associations/has_many_through_associations_test.rb
index 0ac56c6168..6f23a832ef 100644
--- a/activerecord/test/cases/associations/has_many_through_associations_test.rb
+++ b/activerecord/test/cases/associations/has_many_through_associations_test.rb
@@ -55,6 +55,15 @@ class HasManyThroughAssociationsTest < ActiveRecord::TestCase
     assert_equal preloaded, Marshal.load(Marshal.dump(preloaded))
   end
 
+  def test_preload_with_nested_association
+    posts = Post.preload(:author, :author_favorites).to_a
+
+    assert_no_queries do
+      posts.each(&:author)
+      posts.each(&:author_favorites)
+    end
+  end
+
   def test_preload_sti_rhs_class
     developers = Developer.includes(:firms).all.to_a
     assert_no_queries do
diff --git a/activerecord/test/models/author.rb b/activerecord/test/models/author.rb
index 8b5a2fa0c8..3eb8a3a0fa 100644
--- a/activerecord/test/models/author.rb
+++ b/activerecord/test/models/author.rb
@@ -217,6 +217,8 @@ class AuthorAddress < ActiveRecord::Base
 end
 
 class AuthorFavorite < ActiveRecord::Base
+  default_scope { order(id: :asc) }
+
   belongs_to :author
   belongs_to :favorite_author, class_name: "Author"
 end