clone and dup are working on 1.8

activerecord/lib/active_record/base.rb

@@ -1591,19 +1591,28 @@ MSG
         @attributes.frozen?
       end
 
+      # Backport dup from 1.9 so that initialize_dup() gets called
+      unless Object.respond_to?(:initialize_dup)
+        def dup # :nodoc:
+          copy = super
+          copy.initialize_dup(self)
+          copy
+        end
+      end
+
       # Duped objects have no id assigned and are treated as new records. Note
       # that this is a "shallow" copy as it copies the object's attributes
       # only, not its associations. The extent of a "deep" copy is application
       # specific and is therefore left to the application to implement according
       # to its need.
       def initialize_dup(other)
-        super
-        _run_after_initialize_callbacks if respond_to?(:_run_after_initialize_callbacks)
         cloned_attributes = other.clone_attributes(:read_attribute_before_type_cast)
         cloned_attributes.delete(self.class.primary_key)
 
         @attributes = cloned_attributes
 
+        _run_after_initialize_callbacks if respond_to?(:_run_after_initialize_callbacks)
+
         @changed_attributes = {}
         attributes_from_column_definition.each do |attr, orig_value|
           @changed_attributes[attr] = orig_value if field_changed?(attr, orig_value, @attributes[attr])
@@ -1612,7 +1621,7 @@ MSG
         clear_aggregation_cache
         clear_association_cache
         @attributes_cache   = {}
-        @persisted          = false
+        @persisted  = false
 
         ensure_proper_type
         populate_with_current_scope_attributes

activerecord/test/cases/dup_test.rb

@@ -9,6 +9,21 @@ module ActiveRecord
       assert !Topic.new.freeze.dup.frozen?
     end
 
+    def test_not_readonly
+      topic = Topic.first
+
+      duped = topic.dup
+      assert !topic.readonly?, 'should not be readonly'
+    end
+
+    def test_is_readonly
+      topic = Topic.first
+      topic.readonly!
+
+      duped = topic.dup
+      assert topic.readonly?, 'should be readonly'
+    end
+
     def test_dup_not_persisted
       topic = Topic.first
       duped = topic.dup