Fix AM/AR Dirty plugin issues with AR 5.2

lib/mobility/plugins/active_model/dirty.rb

@@ -30,8 +30,9 @@ module Dirty
         def write(locale, value, options = {})
           locale_accessor = Mobility.normalize_locale_accessor(attribute, locale)
           if model.changed_attributes.has_key?(locale_accessor) && model.changed_attributes[locale_accessor] == value
-            model.attributes_changed_by_setter.except!(locale_accessor)
+            model.send(:attributes_changed_by_setter).except!(locale_accessor)
           elsif read(locale, options.merge(fallback: false)) != value
+            model.send(:mobility_changed_attributes) << locale_accessor
             model.send(:attribute_will_change!, locale_accessor)
           end
           super
@@ -63,6 +64,10 @@ def initialize(*attribute_names)
             private :restore_attribute!
           end
 
+          def included(model_class)
+            model_class.include ChangedAttributes
+          end
+
           private
 
           # Get method suffixes. Creating an object just to get the list of
@@ -74,6 +79,19 @@ def method_suffixes
                 include ::ActiveModel::Dirty
               end.attribute_method_matchers.map(&:suffix).select { |m| m =~ /\A_/ }
           end
+
+          # Tracks which translated attributes have been changed, separate from
+          # the default tracking of changes in ActiveModel/ActiveRecord Dirty.
+          # This is required in order for the Mobility ActiveRecord Dirty
+          # plugin to correctly read the value of locale accessors like
+          # +title_en+ in dirty tracking.
+          module ChangedAttributes
+            private
+
+            def mobility_changed_attributes
+              @mobility_changed_attributes ||= Set.new
+            end
+          end
         end
       end
     end

lib/mobility/plugins/active_record/dirty.rb

@@ -34,13 +34,15 @@ def initialize(*attribute_names)
             define_attribute_methods if ::ActiveRecord::VERSION::STRING >= '5.1'
           end
 
-          # Overrides +ActiveRecord::AttributeMethods::ClassMethods#has_attribute+ to treat fallthrough attribute methods
-          # just like "real" attribute methods.
+          # Overrides +ActiveRecord::AttributeMethods::ClassMethods#has_attribute+ and
+          # +ActiveModel::AttributeMethods#_read_attribute+ to treat
+          # fallthrough attribute methods just like "real" attribute methods.
           #
           # @note Patching +has_attribute?+ is necessary as of AR 5.1 due to this commit[https://github.com/rails/rails/commit/4fed08fa787a316fa51f14baca9eae11913f5050].
           #   (I have voiced my opposition to this change here[https://github.com/rails/rails/pull/27963#issuecomment-310092787]).
           # @param [Attributes] attributes
           def included(model_class)
+            super
             names = @attribute_names
             method_name_regex = /\A(#{names.join('|'.freeze)})_([a-z]{2}(_[a-z]{2})?)(=?|\??)\z/.freeze
             has_attribute = Module.new do
@@ -49,6 +51,7 @@ def included(model_class)
               end
             end
             model_class.extend has_attribute
+            model_class.include ReadAttribute if ::ActiveRecord::VERSION::STRING >= '5.2'
           end
 
           private
@@ -94,6 +97,26 @@ def define_attribute_methods
               alias_method :"#{name}_in_database", :"#{name}_was"
             end
           end
+
+          # Overrides _read_attribute to correctly dispatch reads on translated
+          # attributes to their respective setters, rather than to
+          # +@attributes+, which would otherwise return +nil+.
+          #
+          # For background on why this is necessary, see:
+          # https://github.com/shioyama/mobility/issues/115
+          module ReadAttribute
+            # @note We first check if attributes has the key +attr+ to avoid
+            #   doing any extra work in case this is a "normal"
+            #   (non-translated) attribute.
+            def _read_attribute(attr, *args)
+              if @attributes.key?(attr)
+                super
+              else
+                mobility_changed_attributes.include?(attr) ? __send__(attr) : super
+              end
+            end
+            private :_read_attribute
+          end
         end
       end
     end