1 files changed, 42 insertions, 10 deletions

diff --git a/activerecord/lib/active_record/attribute_decorators.rb b/activerecord/lib/active_record/attribute_decorators.rb
index 596161f81d..5b96623b6e 100644
--- a/activerecord/lib/active_record/attribute_decorators.rb
+++ b/activerecord/lib/active_record/attribute_decorators.rb
@@ -4,31 +4,63 @@ module ActiveRecord
 
     included do
       class_attribute :attribute_type_decorations, instance_accessor: false # :internal:
-      self.attribute_type_decorations = Hash.new({})
+      self.attribute_type_decorations = TypeDecorator.new
     end
 
-    module ClassMethods
+    module ClassMethods # :nodoc:
       def decorate_attribute_type(column_name, decorator_name, &block)
+        matcher = ->(name, _) { name == column_name.to_s }
+        key = "_#{column_name}_#{decorator_name}"
+        decorate_matching_attribute_types(matcher, key, &block)
+      end
+
+      def decorate_matching_attribute_types(matcher, decorator_name, &block)
         clear_caches_calculated_from_columns
-        column_name = column_name.to_s
+        decorator_name = decorator_name.to_s
 
         # Create new hashes so we don't modify parent classes
-        decorations_for_column = attribute_type_decorations[column_name]
-        new_decorations = decorations_for_column.merge(decorator_name.to_s => block)
-        self.attribute_type_decorations = attribute_type_decorations.merge(column_name => new_decorations)
+        self.attribute_type_decorations = attribute_type_decorations.merge(decorator_name => [matcher, block])
       end
 
       private
 
       def add_user_provided_columns(*)
         super.map do |column|
-          decorations = attribute_type_decorations[column.name].values
-          decorated_type = decorations.inject(column.cast_type) do |type, block|
-            block.call(type)
-          end
+          decorated_type = attribute_type_decorations.apply(column.name, column.cast_type)
           column.with_type(decorated_type)
         end
       end
     end
+
+    class TypeDecorator # :nodoc:
+      delegate :clear, to: :@decorations
+
+      def initialize(decorations = {})
+        @decorations = decorations
+      end
+
+      def merge(*args)
+        TypeDecorator.new(@decorations.merge(*args))
+      end
+
+      def apply(name, type)
+        decorations = decorators_for(name, type)
+        decorations.inject(type) do |new_type, block|
+          block.call(new_type)
+        end
+      end
+
+      private
+
+      def decorators_for(name, type)
+        matching(name, type).map(&:last)
+      end
+
+      def matching(name, type)
+        @decorations.values.select do |(matcher, _)|
+          matcher.call(name, type)
+        end
+      end
+    end
   end
 end