1 files changed, 53 insertions, 0 deletions
diff --git a/activerecord/lib/active_record/attribute_methods/read.rb b/activerecord/lib/active_record/attribute_methods/read.rb
new file mode 100644
index 0000000000..ffac5313ad
--- /dev/null
+++ b/activerecord/lib/active_record/attribute_methods/read.rb
@@ -0,0 +1,53 @@
+# frozen_string_literal: true
+
+module ActiveRecord
+  module AttributeMethods
+    module Read
+      extend ActiveSupport::Concern
+
+      module ClassMethods # :nodoc:
+        private
+
+          def define_method_attribute(name)
+            sync_with_transaction_state = "sync_with_transaction_state" if name == primary_key
+
+            ActiveModel::AttributeMethods::AttrNames.define_attribute_accessor_method(
+              generated_attribute_methods, name
+            ) do |temp_method_name, attr_name_expr|
+              generated_attribute_methods.module_eval <<-RUBY, __FILE__, __LINE__ + 1
+                def #{temp_method_name}
+                  #{sync_with_transaction_state}
+                  name = #{attr_name_expr}
+                  _read_attribute(name) { |n| missing_attribute(n, caller) }
+                end
+              RUBY
+            end
+          end
+      end
+
+      # Returns the value of the attribute identified by <tt>attr_name</tt> after
+      # it has been typecast (for example, "2004-12-12" in a date column is cast
+      # to a date object, like Date.new(2004, 12, 12)).
+      def read_attribute(attr_name, &block)
+        name = attr_name.to_s
+        if self.class.attribute_alias?(name)
+          name = self.class.attribute_alias(name)
+        end
+
+        primary_key = self.class.primary_key
+        name = primary_key if name == "id" && primary_key
+        sync_with_transaction_state if name == primary_key
+        _read_attribute(name, &block)
+      end
+
+      # This method exists to avoid the expensive primary_key check internally, without
+      # breaking compatibility with the read_attribute API
+      def _read_attribute(attr_name, &block) # :nodoc
+        @attributes.fetch_value(attr_name.to_s, &block)
+      end
+
+      alias :attribute :_read_attribute
+      private :attribute
+    end
+  end
+end