Correctly ignore `mark_for_destruction` without `autosave`

As per the docs, `mark_for_destruction` should do nothing if `autosave`
is not set to true. We normally persist associations on a record no
matter what if the record is a new record, but we were always skipping
records which were `marked_for_destruction?`.

Fixes #20882

2 files changed, 8 insertions, 0 deletions

diff --git a/activerecord/test/cases/autosave_association_test.rb b/activerecord/test/cases/autosave_association_test.rb
index 6b69b96e21..37ec3f1106 100644
--- a/activerecord/test/cases/autosave_association_test.rb
+++ b/activerecord/test/cases/autosave_association_test.rb
@@ -1154,6 +1154,13 @@ class TestAutosaveAssociationOnAHasOneAssociation < ActiveRecord::TestCase
   def test_should_not_load_the_associated_model
     assert_queries(1) { @pirate.catchphrase = 'Arr'; @pirate.save! }
   end
+
+  def test_mark_for_destruction_is_ignored_without_autosave_true
+    ship = ShipWithoutNestedAttributes.new(name: "The Black Flag")
+    ship.parts.build.mark_for_destruction
+
+    assert_not ship.valid?
+  end
 end
 
 class TestAutosaveAssociationOnAHasOneThroughAssociation < ActiveRecord::TestCase
diff --git a/activerecord/test/models/ship.rb b/activerecord/test/models/ship.rb
index fcc533380b..95172e4d3e 100644
--- a/activerecord/test/models/ship.rb
+++ b/activerecord/test/models/ship.rb
@@ -22,6 +22,7 @@ end
 class ShipWithoutNestedAttributes < ActiveRecord::Base
   self.table_name = "ships"
   has_many :prisoners, inverse_of: :ship, foreign_key: :ship_id
+  has_many :parts, class_name: "ShipPart", foreign_key: :ship_id
 
   validates :name, presence: true
 end