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

activerecord/lib/active_record/attribute_methods.rb

@@ -287,11 +287,6 @@ module ActiveRecord
       }
     end
 
-    # Placeholder so it can be overriden when needed by serialization
-    def attributes_for_coder # :nodoc:
-      attributes_before_type_cast
-    end
-
     # Returns an <tt>#inspect</tt>-like string for the value of the
     # attribute +attr_name+. String attributes are truncated upto 50
     # characters, Date and Time attributes are returned in the

activerecord/lib/active_record/attribute_methods/read.rb

@@ -94,7 +94,7 @@ module ActiveRecord
 
         def cacheable_column?(column)
           if attribute_types_cached_by_default == ATTRIBUTE_TYPES_CACHED_BY_DEFAULT
-            ! serialized_attributes.include? column.name
+            true
           else
             attribute_types_cached_by_default.include?(column.type)
           end

activerecord/lib/active_record/attribute_methods/serialization.rb

@@ -76,21 +76,6 @@ module ActiveRecord
       module Behavior # :nodoc:
         extend ActiveSupport::Concern
 
-        module ClassMethods # :nodoc:
-          def initialize_attributes(attributes, options = {})
-            serialized = (options.delete(:serialized) { true }) ? :serialized : :unserialized
-            super(attributes, options)
-
-            serialized_attributes.each do |key, coder|
-              if attributes.key?(key)
-                attributes[key] = Type::Serialized::Attribute.new(coder, attributes[key], serialized)
-              end
-            end
-
-            attributes
-          end
-        end
-
         def should_record_timestamps?
           super || (self.record_timestamps && (attributes.keys & self.class.serialized_attributes.keys).present?)
         end
@@ -106,42 +91,6 @@ module ActiveRecord
             super
           end
         end
-
-        def read_attribute_before_type_cast(attr_name)
-          if self.class.serialized_attributes.include?(attr_name)
-            super.unserialized_value
-          else
-            super
-          end
-        end
-
-        def attributes_before_type_cast
-          super.dup.tap do |attributes|
-            self.class.serialized_attributes.each_key do |key|
-              if attributes.key?(key)
-                attributes[key] = attributes[key].unserialized_value
-              end
-            end
-          end
-        end
-
-        def typecasted_attribute_value(name)
-          if self.class.serialized_attributes.include?(name)
-            @raw_attributes[name].serialized_value
-          else
-            super
-          end
-        end
-
-        def attributes_for_coder
-          attribute_names.each_with_object({}) do |name, attrs|
-            attrs[name] = if self.class.serialized_attributes.include?(name)
-                            @raw_attributes[name].serialized_value
-                          else
-                            read_attribute_before_type_cast(name)
-                          end
-          end
-        end
       end
     end
   end

activerecord/lib/active_record/attribute_methods/write.rb

@@ -53,11 +53,11 @@ module ActiveRecord
       # specified +value+. Empty strings for fixnum and float columns are
       # turned into +nil+.
       def write_attribute(attr_name, value)
-        write_attribute_with_type_cast(attr_name, value, :type_cast_for_write)
+        write_attribute_with_type_cast(attr_name, value, true)
       end
 
       def raw_write_attribute(attr_name, value)
-        write_attribute_with_type_cast(attr_name, value, :raw_type_cast_for_write)
+        write_attribute_with_type_cast(attr_name, value, false)
       end
 
       private
@@ -66,7 +66,7 @@ module ActiveRecord
         write_attribute(attribute_name, value)
       end
 
-      def write_attribute_with_type_cast(attr_name, value, type_cast_method)
+      def write_attribute_with_type_cast(attr_name, value, should_type_cast)
         attr_name = attr_name.to_s
         attr_name = self.class.primary_key if attr_name == 'id' && self.class.primary_key
         @attributes.delete(attr_name)
@@ -78,9 +78,9 @@ module ActiveRecord
           @attributes[attr_name] = value
         end
 
-        if column
-          @raw_attributes[attr_name] = column.public_send(type_cast_method, value)
-        elsif @raw_attributes.has_key?(attr_name)
+        if column && should_type_cast
+          @raw_attributes[attr_name] = column.type_cast_for_write(value)
+        elsif !should_type_cast || @raw_attributes.has_key?(attr_name)
           @raw_attributes[attr_name] = value
         else
           raise ActiveModel::MissingAttributeError, "can't write unknown attribute `#{attr_name}'"

activerecord/lib/active_record/connection_adapters/column.rb

@@ -17,7 +17,7 @@ module ActiveRecord
 
       delegate :type, :precision, :scale, :limit, :klass, :accessor,
         :text?, :number?, :binary?, :serialized?,
-        :type_cast, :type_cast_for_write, :raw_type_cast_for_write, :type_cast_for_database,
+        :type_cast, :type_cast_for_write, :type_cast_for_database,
         :type_cast_for_schema,
         to: :cast_type
 
@@ -52,7 +52,7 @@ module ActiveRecord
       end
 
       def extract_default(default)
-        type_cast(default)
+        type_cast_for_write(type_cast(default))
       end
     end
   end

activerecord/lib/active_record/core.rb

@@ -353,7 +353,7 @@ module ActiveRecord
     #   Post.new.encode_with(coder)
     #   coder # => {"attributes" => {"id" => nil, ... }}
     def encode_with(coder)
-      coder['attributes'] = attributes_for_coder
+      coder['attributes'] = @raw_attributes
     end
 
     # Returns true if +comparison_object+ is the same exact object, or +comparison_object+

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
+      private
 
-        def serialized_value
-          state == :unserialized ? serialize : value
-        end
-
-        def unserialize(v)
-          self.state = :unserialized
-          self.value = coder.load(v)
-        end
-
-        def serialize
-          self.state = :serialized
-          self.value = coder.dump(value)
-        end
+      def is_default_value?(value)
+        value == coder.load(nil)
       end
     end
   end

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
 

activerecord/lib/active_record/validations/uniqueness.rb

@@ -14,7 +14,6 @@ module ActiveRecord
         finder_class = find_finder_class_for(record)
         table = finder_class.arel_table
         value = map_enum_attribute(finder_class, attribute, value)
-        value = deserialize_attribute(record, attribute, value)
 
         relation = build_relation(finder_class, table, attribute, value)
         relation = relation.and(table[finder_class.primary_key.to_sym].not_eq(record.id)) if record.persisted?
@@ -86,12 +85,6 @@ module ActiveRecord
         relation
       end
 
-      def deserialize_attribute(record, attribute, value)
-        coder = record.class.serialized_attributes[attribute.to_s]
-        value = coder.dump value if value && coder
-        value
-      end
-
       def map_enum_attribute(klass, attribute, value)
         mapping = klass.defined_enums[attribute.to_s]
         value = mapping[value] if value && mapping

activerecord/test/cases/adapters/postgresql/composite_test.rb

@@ -93,6 +93,7 @@ class PostgresqlCompositeWithCustomOIDTest < ActiveRecord::TestCase
     end
 
     def type_cast_for_write(value)
+      return if value.nil?
       "(#{value.city},#{value.street})"
     end
   end

activerecord/test/cases/attribute_methods_test.rb

@@ -870,7 +870,7 @@ class AttributeMethodsTest < ActiveRecord::TestCase
   end
 
   def cached_columns
-    Topic.columns.map(&:name) - Topic.serialized_attributes.keys
+    Topic.columns.map(&:name)
   end
 
   def time_related_columns_on_topic

activerecord/test/cases/serialized_attribute_test.rb

@@ -59,8 +59,9 @@ class SerializedAttributeTest < ActiveRecord::TestCase
   def test_serialized_attribute_calling_dup_method
     Topic.serialize :content, JSON
 
-    t = Topic.new(:content => { :foo => :bar }).dup
-    assert_equal({ :foo => :bar }, t.content_before_type_cast)
+    orig = Topic.new(content: { foo: :bar })
+    clone = orig.dup
+    assert_equal(orig.content, clone.content)
   end
 
   def test_serialized_attribute_declared_in_subclass
@@ -103,8 +104,10 @@ class SerializedAttributeTest < ActiveRecord::TestCase
 
   def test_serialized_attribute_should_raise_exception_on_save_with_wrong_type
     Topic.serialize(:content, Hash)
-    topic = Topic.new(:content => "string")
-    assert_raise(ActiveRecord::SerializationTypeMismatch) { topic.save }
+    assert_raise(ActiveRecord::SerializationTypeMismatch) do
+      topic = Topic.new(content: 'string')
+      topic.save
+    end
   end
 
   def test_should_raise_exception_on_serialized_attribute_with_type_mismatch