Fix building has_one through record

Fixes #31762.

4 files changed, 22 insertions, 14 deletions

diff --git a/activerecord/lib/active_record/associations/has_many_through_association.rb b/activerecord/lib/active_record/associations/has_many_through_association.rb
index 24766dd315..59929b8c4e 100644
--- a/activerecord/lib/active_record/associations/has_many_through_association.rb
+++ b/activerecord/lib/active_record/associations/has_many_through_association.rb
@@ -8,9 +8,7 @@ module ActiveRecord
 
       def initialize(owner, reflection)
         super
-
-        @through_records     = {}
-        @through_association = nil
+        @through_records = {}
       end
 
       def concat(*records)
@@ -50,11 +48,6 @@ module ActiveRecord
       end
 
       private
-
-        def through_association
-          @through_association ||= owner.association(through_reflection.name)
-        end
-
         # The through record (built with build_record) is temporarily cached
         # so that it may be reused if insert_record is subsequently called.
         #
diff --git a/activerecord/lib/active_record/associations/has_one_through_association.rb b/activerecord/lib/active_record/associations/has_one_through_association.rb
index 36746f9115..491282adf7 100644
--- a/activerecord/lib/active_record/associations/has_one_through_association.rb
+++ b/activerecord/lib/active_record/associations/has_one_through_association.rb
@@ -6,17 +6,16 @@ module ActiveRecord
     class HasOneThroughAssociation < HasOneAssociation #:nodoc:
       include ThroughAssociation
 
-      def replace(record)
-        create_through_record(record)
+      def replace(record, save = true)
+        create_through_record(record, save)
         self.target = record
       end
 
       private
-
-        def create_through_record(record)
+        def create_through_record(record, save)
           ensure_not_nested
 
-          through_proxy  = owner.association(through_reflection.name)
+          through_proxy  = through_association
           through_record = through_proxy.load_target
 
           if through_record && !record
@@ -30,7 +29,7 @@ module ActiveRecord
 
             if through_record
               through_record.update(attributes)
-            elsif owner.new_record?
+            elsif owner.new_record? || !save
               through_proxy.build(attributes)
             else
               through_proxy.create(attributes)
diff --git a/activerecord/lib/active_record/associations/through_association.rb b/activerecord/lib/active_record/associations/through_association.rb
index 54673b74f7..5afb0bc068 100644
--- a/activerecord/lib/active_record/associations/through_association.rb
+++ b/activerecord/lib/active_record/associations/through_association.rb
@@ -19,6 +19,10 @@ module ActiveRecord
           end
         end
 
+        def through_association
+          @through_association ||= owner.association(through_reflection.name)
+        end
+
         # We merge in these scopes for two reasons:
         #
         #   1. To get the default_scope conditions for any of the other reflections in the chain
diff --git a/activerecord/test/cases/associations/has_one_through_associations_test.rb b/activerecord/test/cases/associations/has_one_through_associations_test.rb
index 1d37457464..8bbd4134fa 100644
--- a/activerecord/test/cases/associations/has_one_through_associations_test.rb
+++ b/activerecord/test/cases/associations/has_one_through_associations_test.rb
@@ -42,6 +42,18 @@ class HasOneThroughAssociationsTest < ActiveRecord::TestCase
     assert_not_nil new_member.club
   end
 
+  def test_creating_association_builds_through_record
+    new_member = Member.create(name: "Chris")
+    new_club = new_member.association(:club).build
+    assert new_member.current_membership
+    assert_equal new_club, new_member.club
+    assert new_club.new_record?
+    assert new_member.current_membership.new_record?
+    assert new_member.save
+    assert new_club.persisted?
+    assert new_member.current_membership.persisted?
+  end
+
   def test_creating_association_builds_through_record_for_new
     new_member = Member.new(name: "Jane")
     new_member.club = clubs(:moustache_club)