1 files changed, 48 insertions, 0 deletions
diff --git a/activerecord/lib/active_record/legacy_yaml_adapter.rb b/activerecord/lib/active_record/legacy_yaml_adapter.rb
new file mode 100644
index 0000000000..ffa095dd94
--- /dev/null
+++ b/activerecord/lib/active_record/legacy_yaml_adapter.rb
@@ -0,0 +1,48 @@
+# frozen_string_literal: true
+
+module ActiveRecord
+  module LegacyYamlAdapter
+    def self.convert(klass, coder)
+      return coder unless coder.is_a?(Psych::Coder)
+
+      case coder["active_record_yaml_version"]
+      when 1, 2 then coder
+      else
+        if coder["attributes"].is_a?(ActiveModel::AttributeSet)
+          Rails420.convert(klass, coder)
+        else
+          Rails41.convert(klass, coder)
+        end
+      end
+    end
+
+    module Rails420
+      def self.convert(klass, coder)
+        attribute_set = coder["attributes"]
+
+        klass.attribute_names.each do |attr_name|
+          attribute = attribute_set[attr_name]
+          if attribute.type.is_a?(Delegator)
+            type_from_klass = klass.type_for_attribute(attr_name)
+            attribute_set[attr_name] = attribute.with_type(type_from_klass)
+          end
+        end
+
+        coder
+      end
+    end
+
+    module Rails41
+      def self.convert(klass, coder)
+        attributes = klass.attributes_builder
+          .build_from_database(coder["attributes"])
+        new_record = coder["attributes"][klass.primary_key].blank?
+
+        {
+          "attributes" => attributes,
+          "new_record" => new_record,
+        }
+      end
+    end
+  end
+end