1 files changed, 22 insertions, 10 deletions

diff --git a/activerecord/lib/active_record/associations/preloader/through_association.rb b/activerecord/lib/active_record/associations/preloader/through_association.rb
index 24aa47bb51..b0203909ce 100644
--- a/activerecord/lib/active_record/associations/preloader/through_association.rb
+++ b/activerecord/lib/active_record/associations/preloader/through_association.rb
@@ -18,7 +18,8 @@ module ActiveRecord
           through_records = owners.map do |owner|
             association = owner.association through_reflection.name
 
-            [owner, Array(association.reader)]
+            center = target_records_from_association(association)
+            [owner, Array(center)]
           end
 
           reset_association owners, through_reflection.name
@@ -37,28 +38,35 @@ module ActiveRecord
             }
           end
 
-          record_offset = {}
-          @preloaded_records.each_with_index do |record,i|
-            record_offset[record] = i
-          end
-
-          through_records.each_with_object({}) { |(lhs,center),records_by_owner|
+          through_records.each_with_object({}) do |(lhs,center), records_by_owner|
             pl_to_middle = center.group_by { |record| middle_to_pl[record] }
 
             records_by_owner[lhs] = pl_to_middle.flat_map do |pl, middles|
               rhs_records = middles.flat_map { |r|
                 association = r.association source_reflection.name
 
-                association.reader
+                target_records_from_association(association)
               }.compact
 
-              rhs_records.sort_by { |rhs| record_offset[rhs] }
+              # Respect the order on `reflection_scope` if it exists, else use the natural order.
+              if reflection_scope.values[:order].present?
+                @id_map ||= id_to_index_map @preloaded_records
+                rhs_records.sort_by { |rhs| @id_map[rhs] }
+              else
+                rhs_records
+              end
             end
-          }
+          end
         end
 
         private
 
+        def id_to_index_map(ids)
+          id_map = {}
+          ids.each_with_index { |id, index| id_map[id] = index }
+          id_map
+        end
+
         def reset_association(owners, association_name)
           should_reset = (through_scope != through_reflection.klass.unscoped) ||
              (reflection.options[:source_type] && through_reflection.collection?)
@@ -91,6 +99,10 @@ module ActiveRecord
 
           scope
         end
+
+        def target_records_from_association(association)
+          association.loaded? ? association.target : association.reader
+        end
       end
     end
   end