Remove most code related to serialized properties

Nearly completely implemented in terms of custom properties.
`_before_type_cast` now stores the raw serialized string consistently,
which removes the need to keep track of "state". The following is now
consistently true:

- `model.serialized == model.reload.serialized`
- A model can be dumped and loaded infinitely without changing
- A model can be saved and reloaded infinitely without changing

2 files changed, 11 insertions, 25 deletions

diff --git a/activerecord/lib/active_record/type/serialized.rb b/activerecord/lib/active_record/type/serialized.rb
index 4052ac0fa0..eac31f6cc3 100644
--- a/activerecord/lib/active_record/type/serialized.rb
+++ b/activerecord/lib/active_record/type/serialized.rb
@@ -10,20 +10,21 @@ module ActiveRecord
       end
 
       def type_cast(value)
-        if value.respond_to?(:unserialized_value)
-          value.unserialized_value(super(value.value))
+        if is_default_value?(value)
+          value
         else
-          super
+          coder.load(super)
         end
       end
 
       def type_cast_for_write(value)
-        Attribute.new(coder, value, :unserialized)
+        return if value.nil?
+        unless is_default_value?(value)
+          coder.dump(value)
+        end
       end
 
-      def raw_type_cast_for_write(value)
-        Attribute.new(coder, value, :serialized)
-      end
+      alias type_cast_for_database type_cast_for_write
 
       def serialized?
         true
@@ -33,24 +34,10 @@ module ActiveRecord
         ActiveRecord::Store::IndifferentHashAccessor
       end
 
-      class Attribute < Struct.new(:coder, :value, :state) # :nodoc:
-        def unserialized_value(v = value)
-          state == :serialized ? unserialize(v) : value
-        end
-
-        def serialized_value
-          state == :unserialized ? serialize : value
-        end
-
-        def unserialize(v)
-          self.state = :unserialized
-          self.value = coder.load(v)
-        end
+      private
 
-        def serialize
-          self.state = :serialized
-          self.value = coder.dump(value)
-        end
+      def is_default_value?(value)
+        value == coder.load(nil)
       end
     end
   end
diff --git a/activerecord/lib/active_record/type/value.rb b/activerecord/lib/active_record/type/value.rb
index 9c1e9dc01e..8cd99df2b4 100644
--- a/activerecord/lib/active_record/type/value.rb
+++ b/activerecord/lib/active_record/type/value.rb
@@ -54,7 +54,6 @@ module ActiveRecord
       def type_cast_for_write(value) # :nodoc:
         value
       end
-      alias_method :raw_type_cast_for_write, :type_cast_for_write # :internal:
 
       private