1 files changed, 7 insertions, 4 deletions
diff --git a/activerecord/lib/active_record/attribute_methods.rb b/activerecord/lib/active_record/attribute_methods.rb
index f4a4e3f605..34ec397aee 100644
--- a/activerecord/lib/active_record/attribute_methods.rb
+++ b/activerecord/lib/active_record/attribute_methods.rb
@@ -1,4 +1,5 @@
 require 'active_support/core_ext/enumerable'
+require 'active_support/core_ext/string/filters'
 require 'mutex_m'
 require 'thread_safe'
 
@@ -90,7 +91,7 @@ module ActiveRecord
 
       def undefine_attribute_methods # :nodoc:
         generated_attribute_methods.synchronize do
-          super if @attribute_methods_generated
+          super if defined?(@attribute_methods_generated) && @attribute_methods_generated
           @attribute_methods_generated = false
         end
       end
@@ -205,9 +206,11 @@ module ActiveRecord
       def column_for_attribute(name)
         column = columns_hash[name.to_s]
         if column.nil?
-          ActiveSupport::Deprecation.warn \
-            "`column_for_attribute` will return a null object for non-existent columns " \
-            "in Rails 5.0. Use `has_attribute?` if you need to check for an attribute's existence."
+          ActiveSupport::Deprecation.warn(<<-MSG.squish)
+            `#column_for_attribute` will return a null object for non-existent
+            columns in Rails 5. Use `#has_attribute?` if you need to check for
+            an attribute's existence.
+          MSG
         end
         column
       end