Refs #28025 nullify *_type column on polymorphic associations on :nu… (#28078)

This PR addresses the issue described in #28025. On `dependent: :nullify` strategy only the foreign key of the relation is nullified. However on polymorphic associations the  `*_type` column is not nullified leaving the record with a NULL `*_id` but the `*_type` column is present.

4 files changed, 45 insertions, 0 deletions

diff --git a/activerecord/test/cases/associations/has_many_associations_test.rb b/activerecord/test/cases/associations/has_many_associations_test.rb
index 5921193374..4b9b55f822 100644
--- a/activerecord/test/cases/associations/has_many_associations_test.rb
+++ b/activerecord/test/cases/associations/has_many_associations_test.rb
@@ -1815,6 +1815,22 @@ class HasManyAssociationsTest < ActiveRecord::TestCase
     assert_equal num_accounts, Account.count
   end
 
+  def test_depends_and_nullify_on_polymorphic_assoc
+    author = PersonWithPolymorphicDependentNullifyComments.create!(first_name: "Laertis")
+    comment = posts(:welcome).comments.first
+    comment.author = author
+    comment.save!
+
+    assert_equal comment.author_id, author.id
+    assert_equal comment.author_type, author.class.name
+
+    author.destroy
+    comment.reload
+
+    assert_nil comment.author_id
+    assert_nil comment.author_type
+  end
+
   def test_restrict_with_exception
     firm = RestrictedWithExceptionFirm.create!(name: "restrict")
     firm.companies.create(name: "child")
diff --git a/activerecord/test/cases/associations/has_one_associations_test.rb b/activerecord/test/cases/associations/has_one_associations_test.rb
index bf574f6637..3e5b5c1275 100644
--- a/activerecord/test/cases/associations/has_one_associations_test.rb
+++ b/activerecord/test/cases/associations/has_one_associations_test.rb
@@ -12,6 +12,9 @@ require "models/bulb"
 require "models/author"
 require "models/image"
 require "models/post"
+require "models/drink_designer"
+require "models/chef"
+require "models/department"
 
 class HasOneAssociationsTest < ActiveRecord::TestCase
   self.use_transactional_tests = false unless supports_savepoints?
@@ -114,6 +117,21 @@ class HasOneAssociationsTest < ActiveRecord::TestCase
     assert_nil Account.find(old_account_id).firm_id
   end
 
+  def test_nullify_on_polymorphic_association
+    department = Department.create!
+    designer = DrinkDesignerWithPolymorphicDependentNullifyChef.create!
+    chef = department.chefs.create!(employable: designer)
+
+    assert_equal chef.employable_id, designer.id
+    assert_equal chef.employable_type, designer.class.name
+
+    designer.destroy!
+    chef.reload
+
+    assert_nil chef.employable_id
+    assert_nil chef.employable_type
+  end
+
   def test_nullification_on_destroyed_association
     developer = Developer.create!(name: "Someone")
     ship = Ship.create!(name: "Planet Caravan", developer: developer)
diff --git a/activerecord/test/models/drink_designer.rb b/activerecord/test/models/drink_designer.rb
index eb6701b84e..8258408f35 100644
--- a/activerecord/test/models/drink_designer.rb
+++ b/activerecord/test/models/drink_designer.rb
@@ -4,5 +4,11 @@ class DrinkDesigner < ActiveRecord::Base
   has_one :chef, as: :employable
 end
 
+class DrinkDesignerWithPolymorphicDependentNullifyChef < ActiveRecord::Base
+  self.table_name = "drink_designers"
+
+  has_one :chef, as: :employable, dependent: :nullify
+end
+
 class MocktailDesigner < DrinkDesigner
 end
diff --git a/activerecord/test/models/person.rb b/activerecord/test/models/person.rb
index 5cba1e440e..c3d15a571a 100644
--- a/activerecord/test/models/person.rb
+++ b/activerecord/test/models/person.rb
@@ -62,6 +62,11 @@ class PersonWithDependentNullifyJobs < ActiveRecord::Base
   has_many :jobs, source: :job, through: :references, dependent: :nullify
 end
 
+class PersonWithPolymorphicDependentNullifyComments < ActiveRecord::Base
+  self.table_name = "people"
+  has_many :comments, as: :author, dependent: :nullify
+end
+
 class LoosePerson < ActiveRecord::Base
   self.table_name = "people"
   self.abstract_class = true