1 files changed, 28 insertions, 12 deletions
diff --git a/activerecord/lib/active_record/attribute_set/builder.rb b/activerecord/lib/active_record/attribute_set/builder.rb
index e85777c335..3bd7c7997b 100644
--- a/activerecord/lib/active_record/attribute_set/builder.rb
+++ b/activerecord/lib/active_record/attribute_set/builder.rb
@@ -1,3 +1,5 @@
+require 'active_record/attribute'
+
 module ActiveRecord
   class AttributeSet # :nodoc:
     class Builder # :nodoc:
@@ -45,8 +47,14 @@ module ActiveRecord
       delegate_hash[key] = value
     end
 
+    def deep_dup
+      dup.tap do |copy|
+        copy.instance_variable_set(:@delegate_hash, delegate_hash.transform_values(&:dup))
+      end
+    end
+
     def initialize_dup(_)
-      @delegate_hash = delegate_hash.transform_values(&:dup)
+      @delegate_hash = Hash[delegate_hash]
       super
     end
 
@@ -60,10 +68,29 @@ module ActiveRecord
       end
     end
 
+    def ==(other)
+      if other.is_a?(LazyAttributeHash)
+        materialize == other.materialize
+      else
+        materialize == other
+      end
+    end
+
     protected
 
     attr_reader :types, :values, :additional_types, :delegate_hash
 
+    def materialize
+      unless @materialized
+        values.each_key { |key| self[key] }
+        types.each_key { |key| self[key] }
+        unless frozen?
+          @materialized = true
+        end
+      end
+      delegate_hash
+    end
+
     private
 
     def assign_default_value(name)
@@ -77,16 +104,5 @@ module ActiveRecord
         delegate_hash[name] = Attribute.uninitialized(name, type)
       end
     end
-
-    def materialize
-      unless @materialized
-        values.each_key { |key| self[key] }
-        types.each_key { |key| self[key] }
-        unless frozen?
-          @materialized = true
-        end
-      end
-      delegate_hash
-    end
   end
 end