Fix reset of the source association when through association is loaded

The special case happens when through association has a custom scope
that is applied to the source association when loading.
In this case, the soucre association would need to be reset after
main association is loaded. See tests.

The special case exists when a through association has

2 files changed, 11 insertions, 3 deletions

diff --git a/activerecord/test/cases/associations/has_many_associations_test.rb b/activerecord/test/cases/associations/has_many_associations_test.rb
index 5fdc5a92fc..38e25a9100 100644
--- a/activerecord/test/cases/associations/has_many_associations_test.rb
+++ b/activerecord/test/cases/associations/has_many_associations_test.rb
@@ -2080,10 +2080,12 @@ class HasManyAssociationsTest < ActiveRecord::TestCase
   end
 
   def test_associations_order_should_be_priority_over_throughs_order
-    david = authors(:david)
+    original = authors(:david)
     expected = [12, 10, 9, 8, 7, 6, 5, 3, 2, 1]
-    assert_equal expected, david.comments_desc.map(&:id)
-    assert_equal expected, Author.includes(:comments_desc).find(david.id).comments_desc.map(&:id)
+    assert_equal expected, original.comments_desc.map(&:id)
+    preloaded = Author.includes(:comments_desc).find(original.id)
+    assert_equal expected, preloaded.comments_desc.map(&:id)
+    assert_equal original.posts_sorted_by_id.first.comments.map(&:id), preloaded.posts_sorted_by_id.first.comments.map(&:id)
   end
 
   def test_dynamic_find_should_respect_association_order_for_through
diff --git a/activerecord/test/cases/associations/nested_through_associations_test.rb b/activerecord/test/cases/associations/nested_through_associations_test.rb
index 5821744530..0b83fd8421 100644
--- a/activerecord/test/cases/associations/nested_through_associations_test.rb
+++ b/activerecord/test/cases/associations/nested_through_associations_test.rb
@@ -610,6 +610,12 @@ class NestedThroughAssociationsTest < ActiveRecord::TestCase
     assert_equal hotel, Hotel.joins(:cake_designers, :drink_designers).take
   end
 
+  def test_has_many_through_reset_source_reflection_after_loading_is_complete
+    preloaded = Category.preload(:ordered_post_comments).find(1, 2).last
+    original = Category.find(2)
+    assert_equal original.ordered_post_comments.ids, preloaded.ordered_post_comments.ids
+  end
+
   private
 
     def assert_includes_and_joins_equal(query, expected, association)