have an actual `NullColumn` object and update docs accordingly.

Follow up to #15438 and #15502.

/cc @sgrif

1 files changed, 5 insertions, 4 deletions

diff --git a/activerecord/lib/active_record/attribute_methods.rb b/activerecord/lib/active_record/attribute_methods.rb
index dccbd48592..e626227e7e 100644
--- a/activerecord/lib/active_record/attribute_methods.rb
+++ b/activerecord/lib/active_record/attribute_methods.rb
@@ -195,8 +195,9 @@ module ActiveRecord
           end
       end
 
-      # Returns the column object for the named attribute. Returns +nil+ if the
-      # named attribute not exists.
+      # Returns the column object for the named attribute.
+      # Returns a +ActiveRecord::ConnectionAdapters::NullColumn+ if the
+      # named attribute does not exist.
       #
       #   class Person < ActiveRecord::Base
       #   end
@@ -206,11 +207,11 @@ module ActiveRecord
       #   # => #<ActiveRecord::ConnectionAdapters::SQLite3Column:0x007ff4ab083980 @name="name", @sql_type="varchar(255)", @null=true, ...>
       #
       #   person.column_for_attribute(:nothing)
-      #   # => #<ActiveRecord::ConnectionAdapters::Column:0xXXX @name=nil, @sql_type=nil, @cast_type=#<Type::Value>, ...>
+      #   # => #<ActiveRecord::ConnectionAdapters::NullColumn:0xXXX @name=nil, @sql_type=nil, @cast_type=#<Type::Value>, ...>
       def column_for_attribute(name)
         name = name.to_s
         columns_hash.fetch(name) do
-          ConnectionAdapters::Column.new(name, nil, Type::Value.new)
+          ConnectionAdapters::NullColumn.new(name)
         end
       end
     end