Add option for class_attribute default (#29270)

* Allow a default value to be declared for class_attribute

* Convert to using class_attribute default rather than explicit setter

* Removed instance_accessor option by mistake

* False is a valid default value

* Documentation

2 files changed, 3 insertions, 7 deletions

diff --git a/activerecord/lib/active_record/attribute_methods/dirty.rb b/activerecord/lib/active_record/attribute_methods/dirty.rb
index bd5003d63a..76987fb8f4 100644
--- a/activerecord/lib/active_record/attribute_methods/dirty.rb
+++ b/activerecord/lib/active_record/attribute_methods/dirty.rb
@@ -14,8 +14,7 @@ module ActiveRecord
           raise "You cannot include Dirty after Timestamp"
         end
 
-        class_attribute :partial_writes, instance_writer: false
-        self.partial_writes = true
+        class_attribute :partial_writes, instance_writer: false, default: true
 
         after_create { changes_internally_applied }
         after_update { changes_internally_applied }
diff --git a/activerecord/lib/active_record/attribute_methods/time_zone_conversion.rb b/activerecord/lib/active_record/attribute_methods/time_zone_conversion.rb
index 321d039ed4..4a8d231503 100644
--- a/activerecord/lib/active_record/attribute_methods/time_zone_conversion.rb
+++ b/activerecord/lib/active_record/attribute_methods/time_zone_conversion.rb
@@ -57,11 +57,8 @@ module ActiveRecord
         mattr_accessor :time_zone_aware_attributes, instance_writer: false
         self.time_zone_aware_attributes = false
 
-        class_attribute :skip_time_zone_conversion_for_attributes, instance_writer: false
-        self.skip_time_zone_conversion_for_attributes = []
-
-        class_attribute :time_zone_aware_types, instance_writer: false
-        self.time_zone_aware_types = [:datetime, :time]
+        class_attribute :skip_time_zone_conversion_for_attributes, instance_writer: false, default: []
+        class_attribute :time_zone_aware_types, instance_writer: false, default: [ :datetime, :time ]
       end
 
       module ClassMethods