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.

1 files changed, 4 insertions, 4 deletions

diff --git a/railties/lib/rails/generators/rails/app/templates/config/initializers/wrap_parameters.rb.tt b/railties/lib/rails/generators/rails/app/templates/config/initializers/wrap_parameters.rb.tt
index 19cbf0e4f1..280f777cc0 100644
--- a/railties/lib/rails/generators/rails/app/templates/config/initializers/wrap_parameters.rb.tt
+++ b/railties/lib/rails/generators/rails/app/templates/config/initializers/wrap_parameters.rb.tt
@@ -9,8 +9,8 @@ ActiveSupport.on_load(:action_controller) do
 end
 
 <%- unless options.skip_active_record? -%>
-# Disable root element in JSON by default.
-ActiveSupport.on_load(:active_record) do
-  self.include_root_in_json = false
-end
+# To enable root element in JSON for ActiveRecord objects.
+# ActiveSupport.on_load(:active_record) do
+#  self.include_root_in_json = true
+# end
 <%- end -%>