Merge pull request #32338 from eugeneius/dont_clobber_foreign_key

Don't unset foreign key when preloading missing record

2 files changed, 4 insertions, 2 deletions

diff --git a/activerecord/lib/active_record/associations/preloader/association.rb b/activerecord/lib/active_record/associations/preloader/association.rb
index 0f38d6bbda..d6f7359055 100644
--- a/activerecord/lib/active_record/associations/preloader/association.rb
+++ b/activerecord/lib/active_record/associations/preloader/association.rb
@@ -42,11 +42,11 @@ module ActiveRecord
 
           def associate_records_to_owner(owner, records)
             association = owner.association(reflection.name)
+            association.loaded!
             if reflection.collection?
-              association.loaded!
               association.target.concat(records)
             else
-              association.target = records.first
+              association.target = records.first unless records.empty?
             end
           end
 
diff --git a/activerecord/test/cases/associations/eager_test.rb b/activerecord/test/cases/associations/eager_test.rb
index f18c6177ac..6e0cf30092 100644
--- a/activerecord/test/cases/associations/eager_test.rb
+++ b/activerecord/test/cases/associations/eager_test.rb
@@ -1218,6 +1218,7 @@ class EagerAssociationTest < ActiveRecord::TestCase
 
     client = assert_queries(2) { Client.preload(:firm).find(c.id) }
     assert_no_queries { assert_nil client.firm }
+    assert_equal c.client_of, client.client_of
   end
 
   def test_preloading_empty_belongs_to_polymorphic
@@ -1225,6 +1226,7 @@ class EagerAssociationTest < ActiveRecord::TestCase
 
     tagging = assert_queries(2) { Tagging.preload(:taggable).find(t.id) }
     assert_no_queries { assert_nil tagging.taggable }
+    assert_equal t.taggable_id, tagging.taggable_id
   end
 
   def test_preloading_through_empty_belongs_to