Make `_before_type_cast` actually be before type cast

- The following is now true for all types, all the time
  - `model.attribute_before_type_cast == given_value`
  - `model.attribute == model.save_and_reload.attribute`
  - `model.attribute == model.dup.attribute`
  - `model.attribute == YAML.load(YAML.dump(model)).attribute`
- Removes the remaining types implementing `type_cast_for_write`
- Simplifies the implementation of time zone aware attributes
- Brings tz aware attributes closer to being implemented as an attribute
  decorator
- Adds additional point of control for custom types

3 files changed, 19 insertions, 8 deletions

diff --git a/activerecord/lib/active_record/type/binary.rb b/activerecord/lib/active_record/type/binary.rb
index bc93f6e1bf..3bf29b5026 100644
--- a/activerecord/lib/active_record/type/binary.rb
+++ b/activerecord/lib/active_record/type/binary.rb
@@ -9,7 +9,16 @@ module ActiveRecord
         true
       end
 
+      def type_cast(value)
+        if value.is_a?(Data)
+          value.to_s
+        else
+          super
+        end
+      end
+
       def type_cast_for_database(value)
+        return if value.nil?
         Data.new(super)
       end
 
diff --git a/activerecord/lib/active_record/type/serialized.rb b/activerecord/lib/active_record/type/serialized.rb
index 0866383de9..a1205fa819 100644
--- a/activerecord/lib/active_record/type/serialized.rb
+++ b/activerecord/lib/active_record/type/serialized.rb
@@ -17,15 +17,17 @@ module ActiveRecord
         end
       end
 
-      def type_cast_for_write(value)
+      def type_cast_from_user(value)
+        type_cast(type_cast_for_database(value))
+      end
+
+      def type_cast_for_database(value)
         return if value.nil?
         unless is_default_value?(value)
           super coder.dump(value)
         end
       end
 
-      alias type_cast_for_database type_cast_for_write
-
       def serialized?
         true
       end
diff --git a/activerecord/lib/active_record/type/value.rb b/activerecord/lib/active_record/type/value.rb
index 1c41b28646..deacc398ef 100644
--- a/activerecord/lib/active_record/type/value.rb
+++ b/activerecord/lib/active_record/type/value.rb
@@ -23,8 +23,12 @@ module ActiveRecord
         cast_value(value) unless value.nil?
       end
 
+      def type_cast_from_user(value)
+        type_cast(value)
+      end
+
       def type_cast_for_database(value)
-        type_cast_for_write(value)
+        value
       end
 
       def type_cast_for_schema(value)
@@ -50,10 +54,6 @@ module ActiveRecord
       def klass # :nodoc:
       end
 
-      def type_cast_for_write(value) # :nodoc:
-        value
-      end
-
       # +old_value+ will always be type-cast.
       # +new_value+ will come straight from the database
       # or from assignment, so it could be anything. Types