Mark nested resources as persisted when loaded from a response.

[dylanahsmith]

See the included regression test which shows the correct behaviour, and fails without the included fix.

Without this fix, saving nested resources results in a create rather than an update.

[travisbot]

This pull request fails (merged cb60edc into da3236c).

[dylanahsmith]

This pull request fails (merged cb60edc into da3236c).

Wasn't experiencing this failure until I removed my Gemfile.lock, updated to the latest rails/master, rebuild and reinstalled activesupport and activemodel, bundle installed, then re-ran the tests. However, the latest activeresource/master has the same test failures now.

Edit: Ran a regression test repeating the above steps in a script.

ab11a2780fe8e059ffc8824df18037773a4f5200 is the first bad commit
commit ab11a2780fe8e059ffc8824df18037773a4f5200
Author: Francesco Rodriguez lrodriguezsanc@gmail.com
Date: Wed Jun 6 01:11:39 2012 -0500

change AMS::JSON.include_root_in_json default value to false

Changes:

* Update `include_root_in_json` default value to false for default value
  to false for `ActiveModel::Serializers::JSON`.
* Remove unnecessary change to include_root_in_json option in
  wrap_parameters template.
* Update `as_json` documentation.
* Fix JSONSerialization tests.

Problem:

It's confusing that AM serializers behave differently from AR,
even when AR objects include AM serializers module.

    class User < ActiveRecord::Base; end

    class Person
      include ActiveModel::Model
      include ActiveModel::AttributeMethods
      include ActiveModel::Serializers::JSON

      attr_accessor :name, :age

      def attributes
        instance_values
      end
    end

    user.as_json
    => {"id"=>1, "name"=>"Konata Izumi", "age"=>16, "awesome"=>true}
    # root is not included

    person.as_json
    => {"person"=>{"name"=>"Francesco", "age"=>22}}
    # root is included

    ActiveRecord::Base.include_root_in_json
    => false

    Person.include_root_in_json
    => true

    # different default values for include_root_in_json

Proposal:

Change the default value of AM serializers to false, update
the misleading documentation and remove unnecessary change
to false of include_root_in_json option with AR objects.

    class User < ActiveRecord::Base; end

    class Person
      include ActiveModel::Model
      include ActiveModel::AttributeMethods
      include ActiveModel::Serializers::JSON

      attr_accessor :name, :age

      def attributes
        instance_values
      end
    end

    user.as_json
    => {"id"=>1, "name"=>"Konata Izumi", "age"=>16, "awesome"=>true}
    # root is not included

    person.as_json
    => {"name"=>"Francesco", "age"=>22}
    # root is not included

    ActiveRecord::Base.include_root_in_json
    => false

    Person.include_root_in_json
    => false

    # same behaviour, more consistent

Fixes #6578.

[mejibyte]

+1.