Refactor serialized types to be partially defined as custom properties

Many of the methods defined in `AttributeMethods::Serialization` can be
refactored onto this type as well, but this is a reasonable small step.
Removes the `Type` class, and the need for `decorate_columns` to handle
serialized types.

10 files changed, 52 insertions, 50 deletions

diff --git a/activerecord/lib/active_record/attribute_methods/serialization.rb b/activerecord/lib/active_record/attribute_methods/serialization.rb
index 47c6f94ba7..e8c27cb8b8 100644
--- a/activerecord/lib/active_record/attribute_methods/serialization.rb
+++ b/activerecord/lib/active_record/attribute_methods/serialization.rb
@@ -58,32 +58,18 @@ module ActiveRecord
                     Coders::YAMLColumn.new(class_name_or_coder)
                   end
 
+          type = columns_hash[attr_name.to_s].cast_type
+          if type.serialized?
+            type = type.subtype
+          end
+          property attr_name, ActiveRecord::Type::Serialized.new(type)
+
           # merge new serialized attribute and create new hash to ensure that each class in inheritance hierarchy
           # has its own hash of own serialized attributes
           self.serialized_attributes = serialized_attributes.merge(attr_name.to_s => coder)
         end
       end
 
-      class Type # :nodoc:
-        delegate :type, :type_cast_for_database, to: :@column
-
-        def initialize(column)
-          @column = column
-        end
-
-        def type_cast(value)
-          if value.state == :serialized
-            value.unserialized_value @column.type_cast value.value
-          else
-            value.unserialized_value
-          end
-        end
-
-        def accessor
-          ActiveRecord::Store::IndifferentHashAccessor
-        end
-      end
-
       class Attribute < Struct.new(:coder, :value, :state) # :nodoc:
         def unserialized_value(v = value)
           state == :serialized ? unserialize(v) : value
diff --git a/activerecord/lib/active_record/connection_adapters/column.rb b/activerecord/lib/active_record/connection_adapters/column.rb
index a62617ab47..42650e332d 100644
--- a/activerecord/lib/active_record/connection_adapters/column.rb
+++ b/activerecord/lib/active_record/connection_adapters/column.rb
@@ -15,8 +15,10 @@ module ActiveRecord
 
       attr_reader :name, :default, :cast_type, :null, :sql_type, :default_function
 
-      delegate :type, :precision, :scale, :limit, :klass, :text?, :number?, :binary?,
-        :type_cast, :type_cast_for_write, :type_cast_for_database, to: :cast_type
+      delegate :type, :precision, :scale, :limit, :klass, :accessor,
+        :text?, :number?, :binary?, :serialized?,
+        :type_cast, :type_cast_for_write, :type_cast_for_database,
+        to: :cast_type
 
       # Instantiates a new column in the table.
       #
diff --git a/activerecord/lib/active_record/connection_adapters/postgresql/column.rb b/activerecord/lib/active_record/connection_adapters/postgresql/column.rb
index 9a5e2d05ef..a579746815 100644
--- a/activerecord/lib/active_record/connection_adapters/postgresql/column.rb
+++ b/activerecord/lib/active_record/connection_adapters/postgresql/column.rb
@@ -35,10 +35,6 @@ module ActiveRecord
         end
       end
       # :startdoc:
-
-      def accessor
-        cast_type.accessor
-      end
     end
   end
 end
diff --git a/activerecord/lib/active_record/model_schema.rb b/activerecord/lib/active_record/model_schema.rb
index a4e10ed2e7..ad6428d8a8 100644
--- a/activerecord/lib/active_record/model_schema.rb
+++ b/activerecord/lib/active_record/model_schema.rb
@@ -224,14 +224,6 @@ module ActiveRecord
       def decorate_columns(columns_hash) # :nodoc:
         return if columns_hash.empty?
 
-        @serialized_column_names ||= self.columns_hash.keys.find_all do |name|
-          serialized_attributes.key?(name)
-        end
-
-        @serialized_column_names.each do |name|
-          columns_hash[name] = AttributeMethods::Serialization::Type.new(columns_hash[name])
-        end
-
         @time_zone_column_names ||= self.columns_hash.find_all do |name, col|
           create_time_zone_conversion_attribute?(name, col)
         end.map!(&:first)
@@ -299,7 +291,6 @@ module ActiveRecord
         @dynamic_methods_hash    = nil
         @inheritance_column      = nil unless defined?(@explicit_inheritance_column) && @explicit_inheritance_column
         @relation                = nil
-        @serialized_column_names = nil
         @time_zone_column_names  = nil
         @cached_time_zone        = nil
       end
diff --git a/activerecord/lib/active_record/properties.rb b/activerecord/lib/active_record/properties.rb
index cc1e8b45c1..7fe59ccce4 100644
--- a/activerecord/lib/active_record/properties.rb
+++ b/activerecord/lib/active_record/properties.rb
@@ -64,6 +64,7 @@ module ActiveRecord
       #   store_listing.price_in_cents # => 1000
       def property(name, cast_type)
         name = name.to_s
+        clear_properties_cache
         # Assign a new hash to ensure that subclasses do not share a hash
         self.user_provided_columns = user_provided_columns.merge(name => connection.new_column(name, nil, cast_type))
       end
@@ -80,9 +81,7 @@ module ActiveRecord
 
       def reset_column_information # :nodoc:
         super
-
-        @columns = nil
-        @columns_hash = nil
+        clear_properties_cache
       end
 
       private
@@ -97,6 +96,11 @@ module ActiveRecord
 
         existing_columns + new_columns
       end
+
+      def clear_properties_cache
+        @columns = nil
+        @columns_hash = nil
+      end
     end
   end
 end
diff --git a/activerecord/lib/active_record/type.rb b/activerecord/lib/active_record/type.rb
index 2c26477201..e9b827886a 100644
--- a/activerecord/lib/active_record/type.rb
+++ b/activerecord/lib/active_record/type.rb
@@ -10,6 +10,7 @@ require 'active_record/type/decimal'
 require 'active_record/type/decimal_without_scale'
 require 'active_record/type/float'
 require 'active_record/type/integer'
+require 'active_record/type/serialized'
 require 'active_record/type/string'
 require 'active_record/type/text'
 require 'active_record/type/time'
diff --git a/activerecord/lib/active_record/type/serialized.rb b/activerecord/lib/active_record/type/serialized.rb
new file mode 100644
index 0000000000..cc7513ca2a
--- /dev/null
+++ b/activerecord/lib/active_record/type/serialized.rb
@@ -0,0 +1,28 @@
+module ActiveRecord
+  module Type
+    class Serialized < SimpleDelegator # :nodoc:
+      attr_reader :subtype
+
+      def initialize(subtype)
+        @subtype = subtype
+        super
+      end
+
+      def type_cast(value)
+        if value.respond_to?(:unserialized_value)
+          value.unserialized_value(super(value.value))
+        else
+          super
+        end
+      end
+
+      def serialized?
+        true
+      end
+
+      def accessor
+        ActiveRecord::Store::IndifferentHashAccessor
+      end
+    end
+  end
+end
diff --git a/activerecord/lib/active_record/type/value.rb b/activerecord/lib/active_record/type/value.rb
index 72d27197d5..a5493be8f2 100644
--- a/activerecord/lib/active_record/type/value.rb
+++ b/activerecord/lib/active_record/type/value.rb
@@ -43,6 +43,10 @@ module ActiveRecord
         false
       end
 
+      def serialized?
+        false
+      end
+
       def klass
         ::Object
       end
diff --git a/activerecord/test/cases/attribute_methods/serialization_test.rb b/activerecord/test/cases/attribute_methods/serialization_test.rb
index 75de773961..2e3bcadab1 100644
--- a/activerecord/test/cases/attribute_methods/serialization_test.rb
+++ b/activerecord/test/cases/attribute_methods/serialization_test.rb
@@ -14,13 +14,13 @@ module ActiveRecord
 
       def test_type_cast_serialized_value
         value = Serialization::Attribute.new(NullCoder.new, "Hello world", :serialized)
-        type = Serialization::Type.new(FakeColumn.new)
+        type = Type::Serialized.new(FakeColumn.new)
         assert_equal "Hello world!", type.type_cast(value)
       end
 
       def test_type_cast_unserialized_value
         value = Serialization::Attribute.new(nil, "Hello world", :unserialized)
-        type = Serialization::Type.new(FakeColumn.new)
+        type = Type::Serialized.new(FakeColumn.new)
         type.type_cast(value)
         assert_equal "Hello world", type.type_cast(value)
       end
diff --git a/activerecord/test/cases/serialized_attribute_test.rb b/activerecord/test/cases/serialized_attribute_test.rb
index c8f9d7cf87..c65a86a6ef 100644
--- a/activerecord/test/cases/serialized_attribute_test.rb
+++ b/activerecord/test/cases/serialized_attribute_test.rb
@@ -235,16 +235,6 @@ class SerializedAttributeTest < ActiveRecord::TestCase
     assert_equal [], light.long_state
   end
 
-  def test_serialized_column_should_not_be_wrapped_twice
-    Topic.serialize(:content, MyObject)
-
-    myobj = MyObject.new('value1', 'value2')
-    Topic.create(content: myobj)
-    Topic.create(content: myobj)
-    type = Topic.column_types["content"]
-    assert !type.instance_variable_get("@column").is_a?(ActiveRecord::AttributeMethods::Serialization::Type)
-  end
-
   def test_serialized_column_should_unserialize_after_update_column
     t = Topic.create(content: "first")
     assert_equal("first", t.content)