Make index_nested_attribute_errors a module instance variable

Followup: rails#42442

Author: byroot

activerecord/lib/active_record.rb

@@ -222,6 +222,9 @@ def self.global_executor_concurrency # :nodoc:
     @global_executor_concurrency ||= nil
   end
 
+  singleton_class.attr_accessor :index_nested_attribute_errors
+  self.index_nested_attribute_errors = false
+
   ##
   # :singleton-method:
   #

activerecord/lib/active_record/autosave_association.rb

@@ -150,7 +150,6 @@ def self.valid_options
 
     included do
       Associations::Builder::Association.extensions << AssociationBuilderExtension
-      mattr_accessor :index_nested_attribute_errors, instance_writer: false, default: false
     end
 
     module ClassMethods # :nodoc:
@@ -335,7 +334,7 @@ def association_valid?(reflection, record, index = nil)
 
         unless valid = record.valid?(context)
           if reflection.options[:autosave]
-            indexed_attribute = !index.nil? && (reflection.options[:index_errors] || ActiveRecord::Base.index_nested_attribute_errors)
+            indexed_attribute = !index.nil? && (reflection.options[:index_errors] || ActiveRecord.index_nested_attribute_errors)
 
             record.errors.group_by_attribute.each { |attribute, errors|
               attribute = normalize_reflection_attribute(indexed_attribute, reflection, index, attribute)

activerecord/test/cases/autosave_association_test.rb

@@ -512,8 +512,8 @@ def test_errors_should_be_indexed_when_passed_as_array
   end
 
   def test_errors_should_be_indexed_when_global_flag_is_set
-    old_attribute_config = ActiveRecord::Base.index_nested_attribute_errors
-    ActiveRecord::Base.index_nested_attribute_errors = true
+    old_attribute_config = ActiveRecord.index_nested_attribute_errors
+    ActiveRecord.index_nested_attribute_errors = true
 
     molecule = Molecule.new
     valid_electron = Electron.new(name: "electron")
@@ -527,7 +527,7 @@ def test_errors_should_be_indexed_when_global_flag_is_set
     assert_equal ["can't be blank"], molecule.errors["electrons[1].name"]
     assert_not_equal ["can't be blank"], molecule.errors["electrons.name"]
   ensure
-    ActiveRecord::Base.index_nested_attribute_errors = old_attribute_config
+    ActiveRecord.index_nested_attribute_errors = old_attribute_config
   end
 
   def test_errors_details_should_be_set
@@ -559,8 +559,8 @@ def test_errors_details_should_be_indexed_when_passed_as_array
   end
 
   def test_errors_details_should_be_indexed_when_global_flag_is_set
-    old_attribute_config = ActiveRecord::Base.index_nested_attribute_errors
-    ActiveRecord::Base.index_nested_attribute_errors = true
+    old_attribute_config = ActiveRecord.index_nested_attribute_errors
+    ActiveRecord.index_nested_attribute_errors = true
 
     molecule = Molecule.new
     valid_electron = Electron.new(name: "electron")
@@ -574,7 +574,7 @@ def test_errors_details_should_be_indexed_when_global_flag_is_set
     assert_equal [{ error: :blank }], molecule.errors.details[:"electrons[1].name"]
     assert_equal [], molecule.errors.details[:"electrons.name"]
   ensure
-    ActiveRecord::Base.index_nested_attribute_errors = old_attribute_config
+    ActiveRecord.index_nested_attribute_errors = old_attribute_config
   end
 
   def test_valid_adding_with_nested_attributes