1 files changed, 36 insertions, 34 deletions

diff --git a/activerecord/lib/active_record/attribute_methods.rb b/activerecord/lib/active_record/attribute_methods.rb
index b4d75d6556..b7edac791e 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'
 
@@ -31,7 +32,7 @@ module ActiveRecord
       end
     }
 
-    BLACKLISTED_CLASS_METHODS = %w(private public protected)
+    BLACKLISTED_CLASS_METHODS = %w(private public protected allocate new name parent superclass)
 
     class AttributeMethodCache
       def initialize
@@ -57,6 +58,8 @@ module ActiveRecord
       end
     end
 
+    class GeneratedAttributeMethods < Module; end # :nodoc:
+
     module ClassMethods
       def inherited(child_class) #:nodoc:
         child_class.initialize_generated_modules
@@ -64,16 +67,18 @@ module ActiveRecord
       end
 
       def initialize_generated_modules # :nodoc:
-        @generated_attribute_methods = Module.new { extend Mutex_m }
+        @generated_attribute_methods = GeneratedAttributeMethods.new { extend Mutex_m }
         @attribute_methods_generated = false
         include @generated_attribute_methods
+
+        super
       end
 
       # Generates all the attribute related methods for columns in the database
       # accessors, mutators and query methods.
       def define_attribute_methods # :nodoc:
         return false if @attribute_methods_generated
-        # Use a mutex; we don't want two thread simultaneously trying to define
+        # Use a mutex; we don't want two threads simultaneously trying to define
         # attribute methods.
         generated_attribute_methods.synchronize do
           return false if @attribute_methods_generated
@@ -86,7 +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
@@ -107,16 +112,17 @@ module ActiveRecord
       #   # => false
       def instance_method_already_implemented?(method_name)
         if dangerous_attribute_method?(method_name)
-          raise DangerousAttributeError, "#{method_name} is defined by Active Record"
+          raise DangerousAttributeError, "#{method_name} is defined by Active Record. Check to make sure that you don't have an attribute or method with the same name."
         end
 
         if superclass == Base
           super
         else
-          # If B < A and A defines its own attribute method, then we don't want to overwrite that.
-          defined = method_defined_within?(method_name, superclass, superclass.generated_attribute_methods)
-          base_defined = Base.method_defined?(method_name) || Base.private_method_defined?(method_name)
-          defined && !base_defined || super
+          # If ThisClass < ... < SomeSuperClass < ... < Base and SomeSuperClass
+          # defines its own attribute method, then we don't want to overwrite that.
+          defined = method_defined_within?(method_name, superclass, Base) &&
+            ! superclass.instance_method(method_name).owner.is_a?(GeneratedAttributeMethods)
+          defined || super
         end
       end
 
@@ -144,7 +150,7 @@ module ActiveRecord
         BLACKLISTED_CLASS_METHODS.include?(method_name.to_s) || class_method_defined_within?(method_name, Base)
       end
 
-      def class_method_defined_within?(name, klass, superklass = klass.superclass) # :nodoc
+      def class_method_defined_within?(name, klass, superklass = klass.superclass) # :nodoc:
         if klass.respond_to?(name, true)
           if superklass.respond_to?(name, true)
             klass.method(name).owner != superklass.method(name).owner
@@ -186,29 +192,33 @@ module ActiveRecord
       end
 
       # Returns the column object for the named attribute.
-      # Returns a +ActiveRecord::ConnectionAdapters::NullColumn+ if the
-      # named attribute does not exist.
+      # Returns nil if the named attribute does not exist.
       #
       #   class Person < ActiveRecord::Base
       #   end
       #
       #   person = Person.new
       #   person.column_for_attribute(:name) # the result depends on the ConnectionAdapter
-      #   # => #<ActiveRecord::ConnectionAdapters::SQLite3Column:0x007ff4ab083980 @name="name", @sql_type="varchar(255)", @null=true, ...>
+      #   # => #<ActiveRecord::ConnectionAdapters::Column:0x007ff4ab083980 @name="name", @sql_type="varchar(255)", @null=true, ...>
       #
       #   person.column_for_attribute(:nothing)
-      #   # => #<ActiveRecord::ConnectionAdapters::NullColumn:0xXXX @name=nil, @sql_type=nil, @cast_type=#<Type::Value>, ...>
+      #   # => nil
       def column_for_attribute(name)
-        name = name.to_s
-        columns_hash.fetch(name) do
-          ConnectionAdapters::NullColumn.new(name)
+        column = columns_hash[name.to_s]
+        if column.nil?
+          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
     end
 
     # A Person object with a name attribute can ask <tt>person.respond_to?(:name)</tt>,
     # <tt>person.respond_to?(:name=)</tt>, and <tt>person.respond_to?(:name?)</tt>
-    # which will all return +true+. It also define the attribute methods if they have
+    # which will all return +true+. It also defines the attribute methods if they have
     # not been generated.
     #
     #   class Person < ActiveRecord::Base
@@ -230,7 +240,7 @@ module ActiveRecord
       # For queries selecting a subset of columns, return false for unselected columns.
       # We check defined?(@attributes) not to issue warnings if called on objects that
       # have been allocated but not yet initialized.
-      if defined?(@attributes) && @attributes.any? && self.class.column_names.include?(name)
+      if defined?(@attributes) && self.class.column_names.include?(name)
         return has_attribute?(name)
       end
 
@@ -247,7 +257,7 @@ module ActiveRecord
     #   person.has_attribute?('age')    # => true
     #   person.has_attribute?(:nothing) # => false
     def has_attribute?(attr_name)
-      @attributes.has_key?(attr_name.to_s)
+      @attributes.key?(attr_name.to_s)
     end
 
     # Returns an array of names for the attributes available on this object.
@@ -271,15 +281,13 @@ module ActiveRecord
     #   person.attributes
     #   # => {"id"=>3, "created_at"=>Sun, 21 Oct 2012 04:53:04, "updated_at"=>Sun, 21 Oct 2012 04:53:04, "name"=>"Francesco", "age"=>22}
     def attributes
-      attribute_names.each_with_object({}) { |name, attrs|
-        attrs[name] = read_attribute(name)
-      }
+      @attributes.to_hash
     end
 
     # Returns an <tt>#inspect</tt>-like string for the value of the
-    # attribute +attr_name+. String attributes are truncated upto 50
+    # attribute +attr_name+. String attributes are truncated up to 50
     # characters, Date and Time attributes are returned in the
-    # <tt>:db</tt> format, Array attributes are truncated upto 10 values.
+    # <tt>:db</tt> format, Array attributes are truncated up to 10 values.
     # Other attributes return the value of <tt>#inspect</tt> without
     # modification.
     #
@@ -324,7 +332,7 @@ module ActiveRecord
     #   task.attribute_present?(:title)   # => true
     #   task.attribute_present?(:is_done) # => true
     def attribute_present?(attribute)
-      value = read_attribute(attribute)
+      value = _read_attribute(attribute)
       !value.nil? && !(value.respond_to?(:empty?) && value.empty?)
     end
 
@@ -367,12 +375,6 @@ module ActiveRecord
 
     protected
 
-    def clone_attributes # :nodoc:
-      @attributes.each_with_object({}) do |(name, attr), h|
-        h[name] = attr.dup
-      end
-    end
-
     def clone_attribute_value(reader_method, attribute_name) # :nodoc:
       value = send(reader_method, attribute_name)
       value.duplicable? ? value.clone : value
@@ -390,7 +392,7 @@ module ActiveRecord
 
     def attribute_method?(attr_name) # :nodoc:
       # We check defined? because Syck calls respond_to? before actually calling initialize.
-      defined?(@attributes) && @attributes.include?(attr_name)
+      defined?(@attributes) && @attributes.key?(attr_name)
     end
 
     private
@@ -431,7 +433,7 @@ module ActiveRecord
     end
 
     def typecasted_attribute_value(name)
-      read_attribute(name)
+      _read_attribute(name)
     end
   end
 end