Add a warning for enum elements with 'not_' prefix.

When a enum element contains the prefix 'not_'. I warns to users
to be aware of this new feature.

Example code:
    class Foo < ActiveRecord::Base
      enum status: [:sent, :not_sent]
    end

1 files changed, 9 insertions, 0 deletions

diff --git a/activerecord/lib/active_record/enum.rb b/activerecord/lib/active_record/enum.rb
index 8077630aeb..fc49f752aa 100644
--- a/activerecord/lib/active_record/enum.rb
+++ b/activerecord/lib/active_record/enum.rb
@@ -200,6 +200,8 @@ module ActiveRecord
             # scope :active, -> { where(status: 0) }
             # scope :not_active, -> { where.not(status: 0) }
             if enum_scopes != false
+              klass.send(:detect_negative_condition!, value_method_name)
+
               klass.send(:detect_enum_conflict!, name, value_method_name, true)
               klass.scope value_method_name, -> { where(attr => value) }
 
@@ -261,5 +263,12 @@ module ActiveRecord
           source: source
         }
       end
+
+      def detect_negative_condition!(method_name)
+        if method_name.start_with?("not_") && logger
+          logger.warn "An enum element in #{self.name} uses the prefix 'not_'." \
+            " This will cause a conflict with auto generated negative scopes."
+        end
+      end
   end
 end