Error calling dup() on ActiveRecord model with serialized field

[gmcnaughton]

Starting with Rails >=3.2.2, I get the following error when calling dup() on a model with a serialized field:

# app/models/my_obj.rb
class MyObj < ActiveRecord::Base
  serialize :content, JSON
end

$ rails c
1.9.3-p0 :001 > MyObj.new(:content => {"a" => "b"}).dup
TypeError: can't convert Hash into String
  from gems/json-1.6.6/lib/json/common.rb:148:in `initialize'
  from gems/json-1.6.6/lib/json/common.rb:148:in `new'
  from gems/json-1.6.6/lib/json/common.rb:148:in `parse'
  from gems/json-1.6.6/lib/json/common.rb:320:in `load'
  from gems/activerecord-3.2.3/lib/active_record/attribute_methods/serialization.rb:24:in `unserialize'
  from gems/activerecord-3.2.3/lib/active_record/attribute_methods/serialization.rb:15:in `unserialized_value'
  from gems/activerecord-3.2.3/lib/active_record/attribute_methods/read.rb:82:in `__temp__'
  from gems/activerecord-3.2.3/lib/active_record/attribute_methods/read.rb:46:in `type_cast_attribute'
  from gems/activerecord-3.2.3/lib/active_record/attribute_methods/read.rb:126:in `read_attribute'
  from gems/activerecord-3.2.3/lib/active_record/attribute_methods.rb:200:in `attribute_for_inspect'
  from gems/activerecord-3.2.3/lib/active_record/base.rb:643:in `block in inspect'
  from gems/activerecord-3.2.3/lib/active_record/base.rb:641:in `collect'
  from gems/activerecord-3.2.3/lib/active_record/base.rb:641:in `inspect'
  from gems/railties-3.2.3/lib/rails/commands/console.rb:47:in `start'
  from gems/railties-3.2.3/lib/rails/commands/console.rb:8:in `start'
  from gems/railties-3.2.3/lib/rails/commands.rb:41:in `<top (required)>'
  from script/rails:6:in `require'
  from script/rails:6:in `<main>'1.9.3-p0 :002

The above code works on Rails 3.2.1. It appears to be related to this commit for issue #4837.

The problem appears to be that after duping, the code tries to unserialize an already-unserialized value. The JSON parser chokes when it receives a Hash instead of a string.

[kennyj]

@gmcnaughton
I can reproduce this issue, and I fix it by the above commit (plan 1).

I guess we have new problem when merging my fix. Because I changed initialized_attributes method's signiture.

If we don't change it, I think the following code also fix it (plan 2).
What do you think ?

$ vim core.rb

def initialize_dup(other)
  cloned_attributes = other.clone_attributes(:read_attribute_before_type_cast)
  serialized_attributes.each { |key, coder| cloned_attributes[key] = coder.dump(cloned_attributes[key]) } # ★added
  self.class.initialize_attributes(cloned_attributes)
  ...

cc/ @jonleighton

[gmcnaughton]

Thanks for the test case and the patch! Either solution sounds good to me, but I'll defer since I don't know the code :)

[kennyj]

Thanks for your confirmation !
Anyway, I sent PR :-)

[jrreed]

+1

[jtokash]

+1

[gmcnaughton]

Thanks guys!