Don't redefine autosave association callbacks in nested attrs

These callbacks will already have been defined when the association was
built. The check against `reflection.autosave` happens at call time, not
at define time, so simply modifying the reflection is sufficient.

Fixes #18704

6 files changed, 20 insertions, 1 deletions

diff --git a/activerecord/CHANGELOG.md b/activerecord/CHANGELOG.md
index 22b1c8e95b..c0ebb892aa 100644
--- a/activerecord/CHANGELOG.md
+++ b/activerecord/CHANGELOG.md
@@ -1,3 +1,10 @@
+*   Don't define autosave association callbacks twice from
+    `accepts_nested_attributes_for`.
+
+    Fixes #18704.
+
+    *Sean Griffin*
+
 *   Integer types will no longer raise a `RangeError` when assigning an
     attribute, but will instead raise when going to the database.
 
diff --git a/activerecord/lib/active_record/nested_attributes.rb b/activerecord/lib/active_record/nested_attributes.rb
index 846e1162a9..919bbfa649 100644
--- a/activerecord/lib/active_record/nested_attributes.rb
+++ b/activerecord/lib/active_record/nested_attributes.rb
@@ -312,7 +312,6 @@ module ActiveRecord
         attr_names.each do |association_name|
           if reflection = _reflect_on_association(association_name)
             reflection.autosave = true
-            add_autosave_association_callbacks(reflection)
 
             nested_attributes_options = self.nested_attributes_options.dup
             nested_attributes_options[association_name.to_sym] = options
diff --git a/activerecord/test/cases/nested_attributes_test.rb b/activerecord/test/cases/nested_attributes_test.rb
index 8bc42b8890..a9e93ad1b6 100644
--- a/activerecord/test/cases/nested_attributes_test.rb
+++ b/activerecord/test/cases/nested_attributes_test.rb
@@ -1037,4 +1037,14 @@ class TestHasManyAutosaveAssociationWhichItselfHasAutosaveAssociations < ActiveR
     ShipPart.create!(:ship => @ship, :name => "Stern")
     assert_no_queries { @ship.valid? }
   end
+
+  test "circular references do not perform unnecessary queries" do
+    ship = Ship.new(name: "The Black Rock")
+    part = ship.parts.build(name: "Stern")
+    ship.treasures.build(looter: part)
+
+    assert_queries 3 do
+      ship.save!
+    end
+  end
 end
diff --git a/activerecord/test/models/ship.rb b/activerecord/test/models/ship.rb
index c2f6d492d8..312caef604 100644
--- a/activerecord/test/models/ship.rb
+++ b/activerecord/test/models/ship.rb
@@ -4,6 +4,7 @@ class Ship < ActiveRecord::Base
   belongs_to :pirate
   belongs_to :update_only_pirate, :class_name => 'Pirate'
   has_many :parts, :class_name => 'ShipPart'
+  has_many :treasures
 
   accepts_nested_attributes_for :parts, :allow_destroy => true
   accepts_nested_attributes_for :pirate, :allow_destroy => true, :reject_if => proc(&:empty?)
diff --git a/activerecord/test/models/treasure.rb b/activerecord/test/models/treasure.rb
index a69d3fd3df..ffc65466d5 100644
--- a/activerecord/test/models/treasure.rb
+++ b/activerecord/test/models/treasure.rb
@@ -1,6 +1,7 @@
 class Treasure < ActiveRecord::Base
   has_and_belongs_to_many :parrots
   belongs_to :looter, :polymorphic => true
+  belongs_to :ship
 
   has_many :price_estimates, :as => :estimate_of
   has_and_belongs_to_many :rich_people, join_table: 'peoples_treasures', validate: false
diff --git a/activerecord/test/schema/schema.rb b/activerecord/test/schema/schema.rb
index 21b23d8e0c..1add85cc05 100644
--- a/activerecord/test/schema/schema.rb
+++ b/activerecord/test/schema/schema.rb
@@ -772,6 +772,7 @@ ActiveRecord::Schema.define do
     t.column :type, :string
     t.column :looter_id, :integer
     t.column :looter_type, :string
+    t.belongs_to :ship
   end
 
   create_table :tyres, force: true do |t|