Only replace association keys if they've changed [5.2 Regression]

activerecord/lib/active_record/associations/association.rb

@@ -76,6 +76,11 @@ def target=(target)
         loaded!
       end
 
+      def preloaded_target=(target) #:nodoc:
+        @target = target
+        loaded!
+      end
+
       def scope
         target_scope.merge!(association_scope)
       end

activerecord/lib/active_record/associations/preloader/association.rb

@@ -46,7 +46,7 @@ def associate_records_to_owner(owner, records)
             if reflection.collection?
               association.target.concat(records)
             else
-              association.target = records.first unless records.empty?
+              association.preloaded_target = records.first unless records.empty?
             end
           end
 

activerecord/test/cases/associations/belongs_to_associations_test.rb

@@ -1213,6 +1213,23 @@ def test_multiple_counter_cache_with_after_create_update
       end
     end
   end
+
+  test "associations on destroyed models can be preloaded" do
+    post = posts(:welcome)
+    SelfDestructingComment.create!(post_id: post.id, body: "body")
+
+    comment = SelfDestructingComment.preload(:post).first
+    assert_equal post, comment.post
+  end
+end
+
+class SelfDestructingComment < ActiveRecord::Base
+  self.table_name = :comments
+  self.inheritance_column = nil
+
+  belongs_to :post
+
+  after_find { destroy! }
 end
 
 class BelongsToWithForeignKeyTest < ActiveRecord::TestCase