1 files changed, 28 insertions, 91 deletions

diff --git a/activemodel/lib/active_model/dirty.rb b/activemodel/lib/active_model/dirty.rb
index 0d9e761b1e..ab2c9d04ae 100644
--- a/activemodel/lib/active_model/dirty.rb
+++ b/activemodel/lib/active_model/dirty.rb
@@ -1,7 +1,5 @@
 # frozen_string_literal: true
 
-require "active_support/hash_with_indifferent_access"
-require "active_support/core_ext/object/duplicable"
 require "active_model/attribute_mutation_tracker"
 
 module ActiveModel
@@ -122,9 +120,6 @@ module ActiveModel
     extend ActiveSupport::Concern
     include ActiveModel::AttributeMethods
 
-    OPTION_NOT_GIVEN = Object.new # :nodoc:
-    private_constant :OPTION_NOT_GIVEN
-
     included do
       attribute_method_suffix "_changed?", "_change", "_will_change!", "_was"
       attribute_method_suffix "_previously_changed?", "_previous_change"
@@ -145,10 +140,9 @@ module ActiveModel
     # +mutations_from_database+ to +mutations_before_last_save+ respectively.
     def changes_applied
       unless defined?(@attributes)
-        @previously_changed = changes
+        mutations_from_database.finalize_changes
       end
       @mutations_before_last_save = mutations_from_database
-      @attributes_changed_by_setter = ActiveSupport::HashWithIndifferentAccess.new
       forget_attribute_assignments
       @mutations_from_database = nil
     end
@@ -159,7 +153,7 @@ module ActiveModel
     #   person.name = 'bob'
     #   person.changed? # => true
     def changed?
-      changed_attributes.present?
+      mutations_from_database.any_changes?
     end
 
     # Returns an array with the name of the attributes with unsaved changes.
@@ -168,42 +162,37 @@ module ActiveModel
     #   person.name = 'bob'
     #   person.changed # => ["name"]
     def changed
-      changed_attributes.keys
+      mutations_from_database.changed_attribute_names
     end
 
     # Handles <tt>*_changed?</tt> for +method_missing+.
-    def attribute_changed?(attr, from: OPTION_NOT_GIVEN, to: OPTION_NOT_GIVEN) # :nodoc:
-      !!changes_include?(attr) &&
-        (to == OPTION_NOT_GIVEN || to == _read_attribute(attr)) &&
-        (from == OPTION_NOT_GIVEN || from == changed_attributes[attr])
+    def attribute_changed?(attr_name, **options) # :nodoc:
+      mutations_from_database.changed?(attr_name.to_s, options)
     end
 
     # Handles <tt>*_was</tt> for +method_missing+.
-    def attribute_was(attr) # :nodoc:
-      attribute_changed?(attr) ? changed_attributes[attr] : _read_attribute(attr)
+    def attribute_was(attr_name) # :nodoc:
+      mutations_from_database.original_value(attr_name.to_s)
     end
 
     # Handles <tt>*_previously_changed?</tt> for +method_missing+.
-    def attribute_previously_changed?(attr) #:nodoc:
-      previous_changes_include?(attr)
+    def attribute_previously_changed?(attr_name) # :nodoc:
+      mutations_before_last_save.changed?(attr_name.to_s)
     end
 
     # Restore all previous data of the provided attributes.
-    def restore_attributes(attributes = changed)
-      attributes.each { |attr| restore_attribute! attr }
+    def restore_attributes(attr_names = changed)
+      attr_names.each { |attr_name| restore_attribute!(attr_name) }
     end
 
     # Clears all dirty data: current changes and previous changes.
     def clear_changes_information
-      @previously_changed = ActiveSupport::HashWithIndifferentAccess.new
       @mutations_before_last_save = nil
-      @attributes_changed_by_setter = ActiveSupport::HashWithIndifferentAccess.new
       forget_attribute_assignments
       @mutations_from_database = nil
     end
 
     def clear_attribute_changes(attr_names)
-      attributes_changed_by_setter.except!(*attr_names)
       attr_names.each do |attr_name|
         clear_attribute_change(attr_name)
       end
@@ -216,13 +205,7 @@ module ActiveModel
     #   person.name = 'robert'
     #   person.changed_attributes # => {"name" => "bob"}
     def changed_attributes
-      # This should only be set by methods which will call changed_attributes
-      # multiple times when it is known that the computed value cannot change.
-      if defined?(@cached_changed_attributes)
-        @cached_changed_attributes
-      else
-        attributes_changed_by_setter.reverse_merge(mutations_from_database.changed_values).freeze
-      end
+      mutations_from_database.changed_values
     end
 
     # Returns a hash of changed attributes indicating their original
@@ -232,9 +215,7 @@ module ActiveModel
     #   person.name = 'bob'
     #   person.changes # => { "name" => ["bill", "bob"] }
     def changes
-      cache_changed_attributes do
-        ActiveSupport::HashWithIndifferentAccess[changed.map { |attr| [attr, attribute_change(attr)] }]
-      end
+      mutations_from_database.changes
     end
 
     # Returns a hash of attributes that were changed before the model was saved.
@@ -244,27 +225,23 @@ module ActiveModel
     #   person.save
     #   person.previous_changes # => {"name" => ["bob", "robert"]}
     def previous_changes
-      @previously_changed ||= ActiveSupport::HashWithIndifferentAccess.new
-      @previously_changed.merge(mutations_before_last_save.changes)
+      mutations_before_last_save.changes
     end
 
     def attribute_changed_in_place?(attr_name) # :nodoc:
-      mutations_from_database.changed_in_place?(attr_name)
+      mutations_from_database.changed_in_place?(attr_name.to_s)
     end
 
     private
       def clear_attribute_change(attr_name)
-        mutations_from_database.forget_change(attr_name)
+        mutations_from_database.forget_change(attr_name.to_s)
       end
 
       def mutations_from_database
-        unless defined?(@mutations_from_database)
-          @mutations_from_database = nil
-        end
         @mutations_from_database ||= if defined?(@attributes)
           ActiveModel::AttributeMutationTracker.new(@attributes)
         else
-          NullMutationTracker.instance
+          ActiveModel::ForcedMutationTracker.new(self)
         end
       end
 
@@ -276,68 +253,28 @@ module ActiveModel
         @mutations_before_last_save ||= ActiveModel::NullMutationTracker.instance
       end
 
-      def cache_changed_attributes
-        @cached_changed_attributes = changed_attributes
-        yield
-      ensure
-        clear_changed_attributes_cache
-      end
-
-      def clear_changed_attributes_cache
-        remove_instance_variable(:@cached_changed_attributes) if defined?(@cached_changed_attributes)
-      end
-
-      # Returns +true+ if attr_name is changed, +false+ otherwise.
-      def changes_include?(attr_name)
-        attributes_changed_by_setter.include?(attr_name) || mutations_from_database.changed?(attr_name)
-      end
-      alias attribute_changed_by_setter? changes_include?
-
-      # Returns +true+ if attr_name were changed before the model was saved,
-      # +false+ otherwise.
-      def previous_changes_include?(attr_name)
-        previous_changes.include?(attr_name)
-      end
-
       # Handles <tt>*_change</tt> for +method_missing+.
-      def attribute_change(attr)
-        [changed_attributes[attr], _read_attribute(attr)] if attribute_changed?(attr)
+      def attribute_change(attr_name)
+        mutations_from_database.change_to_attribute(attr_name.to_s)
       end
 
       # Handles <tt>*_previous_change</tt> for +method_missing+.
-      def attribute_previous_change(attr)
-        previous_changes[attr]
+      def attribute_previous_change(attr_name)
+        mutations_before_last_save.change_to_attribute(attr_name.to_s)
       end
 
       # Handles <tt>*_will_change!</tt> for +method_missing+.
-      def attribute_will_change!(attr)
-        unless attribute_changed?(attr)
-          begin
-            value = _read_attribute(attr)
-            value = value.duplicable? ? value.clone : value
-          rescue TypeError, NoMethodError
-          end
-
-          set_attribute_was(attr, value)
-        end
-        mutations_from_database.force_change(attr)
+      def attribute_will_change!(attr_name)
+        mutations_from_database.force_change(attr_name.to_s)
       end
 
       # Handles <tt>restore_*!</tt> for +method_missing+.
-      def restore_attribute!(attr)
-        if attribute_changed?(attr)
-          __send__("#{attr}=", changed_attributes[attr])
-          clear_attribute_changes([attr])
+      def restore_attribute!(attr_name)
+        attr_name = attr_name.to_s
+        if attribute_changed?(attr_name)
+          __send__("#{attr_name}=", attribute_was(attr_name))
+          clear_attribute_change(attr_name)
         end
       end
-
-      def attributes_changed_by_setter
-        @attributes_changed_by_setter ||= ActiveSupport::HashWithIndifferentAccess.new
-      end
-
-      # Force an attribute to have a particular "before" value
-      def set_attribute_was(attr, old_value)
-        attributes_changed_by_setter[attr] = old_value
-      end
   end
 end