Add support for top level jsonapi member.

CHANGELOG.md

@@ -17,6 +17,7 @@ Features:
 - [#1158](https://github.com/rails-api/active_model_serializers/pull/1158) Add support for wildcards in `include` option (@beauby)
 - [#1127](https://github.com/rails-api/active_model_serializers/pull/1127) Add support for nested
     associations for JSON and Attributes adapters via the `include` option (@NullVoxPopuli, @beauby).
+- [#1050](https://github.com/rails-api/active_model_serializers/pull/1050) Add support for toplevel jsonapi member (@beauby, @bf4)
 
 Fixes:
 

docs/general/configuration_options.md

@@ -9,3 +9,11 @@ The following configuration options can be set on `ActiveModel::Serializer.confi
 ## JSON API
 
 - `jsonapi_resource_type`: Whether the `type` attributes of resources should be singular or plural. Possible values: `:singular, :plural`. Default: `:plural`.
+- `jsonapi_include_toplevel_object`: Whether to include a [top level JSON API member](http://jsonapi.org/format/#document-jsonapi-object)
+   in the response document.
+   Default: `false`.
+- Used when `jsonapi_include_toplevel_object` is `true`:
+  - `jsonapi_version`: The latest version of the spec the API conforms to.
+    Default: `'1.0'`.
+  - `jsonapi_toplevel_meta`: Optional metadata. Not included if empty.
+    Default: `{}`.

lib/active_model/serializer.rb

@@ -1,5 +1,4 @@
 require 'thread_safe'
-require 'active_model/serializer/adapter'
 require 'active_model/serializer/array_serializer'
 require 'active_model/serializer/include_tree'
 require 'active_model/serializer/associations'
@@ -11,6 +10,7 @@ module ActiveModel
   class Serializer
     include Configuration
     include Associations
+    require 'active_model/serializer/adapter'
 
     # Matches
     #  "c:/git/emberjs/ember-crm-backend/app/serializers/lead_serializer.rb:1:in `<top (required)>'"

lib/active_model/serializer/adapter/json_api.rb

@@ -6,6 +6,41 @@ module ActiveModel
         autoload :PaginationLinks
         autoload :FragmentCache
 
+        # TODO: if we like this abstraction and other API objects to it,
+        # then extract to its own file and require it.
+        module ApiObjects
+          module JsonApi
+            ActiveModel::Serializer.config.jsonapi_version = '1.0'
+            ActiveModel::Serializer.config.jsonapi_toplevel_meta = {}
+            # Make JSON API top-level jsonapi member opt-in
+            # ref: http://jsonapi.org/format/#document-top-level
+            ActiveModel::Serializer.config.jsonapi_include_toplevel_object = false
+
+            module_function
+
+            def add!(hash)
+              hash.merge!(object) if include_object?
+            end
+
+            def include_object?
+              ActiveModel::Serializer.config.jsonapi_include_toplevel_object
+            end
+
+            # TODO: see if we can cache this
+            def object
+              object = {
+                jsonapi: {
+                  version: ActiveModel::Serializer.config.jsonapi_version,
+                  meta: ActiveModel::Serializer.config.jsonapi_toplevel_meta
+                }
+              }
+              object[:jsonapi].reject! { |_, v| v.blank? }
+
+              object
+            end
+          end
+        end
+
         def initialize(serializer, options = {})
           super
           @include_tree = IncludeTree.from_include_args(options[:include])
@@ -21,11 +56,16 @@ module ActiveModel
         def serializable_hash(options = nil)
           options ||= {}
 
-          if serializer.respond_to?(:each)
-            serializable_hash_for_collection(options)
-          else
-            serializable_hash_for_single_resource(options)
-          end
+          hash =
+            if serializer.respond_to?(:each)
+              serializable_hash_for_collection(options)
+            else
+              serializable_hash_for_single_resource(options)
+            end
+
+          ApiObjects::JsonApi.add!(hash)
+
+          hash
         end
 
         def fragment_cache(cached_hash, non_cached_hash)

lib/active_model/serializer/configuration.rb

@@ -4,6 +4,8 @@ module ActiveModel
       include ActiveSupport::Configurable
       extend ActiveSupport::Concern
 
+      # Configuration options may also be set in
+      # Serializers and Adapters
       included do |base|
         base.config.array_serializer = ActiveModel::Serializer::ArraySerializer
         base.config.adapter = :attributes

test/adapter/json_api/toplevel_jsonapi_test.rb

@@ -0,0 +1,84 @@
+require 'test_helper'
+
+module ActiveModel
+  class Serializer
+    module Adapter
+      class JsonApi
+        class TopLevelJsonApiTest < Minitest::Test
+          def setup
+            @author = Author.new(id: 1, name: 'Steve K.')
+            @author.bio = nil
+            @author.roles = []
+            @blog = Blog.new(id: 23, name: 'AMS Blog')
+            @post = Post.new(id: 42, title: 'New Post', body: 'Body')
+            @anonymous_post = Post.new(id: 43, title: 'Hello!!', body: 'Hello, world!!')
+            @comment = Comment.new(id: 1, body: 'ZOMG A COMMENT')
+            @post.comments = [@comment]
+            @post.blog = @blog
+            @anonymous_post.comments = []
+            @anonymous_post.blog = nil
+            @comment.post = @post
+            @comment.author = nil
+            @post.author = @author
+            @anonymous_post.author = nil
+            @blog = Blog.new(id: 1, name: 'My Blog!!')
+            @blog.writer = @author
+            @blog.articles = [@post, @anonymous_post]
+            @author.posts = []
+          end
+
+          def test_toplevel_jsonapi_defaults_to_false
+            assert_equal config.fetch(:jsonapi_include_toplevel_object), false
+          end
+
+          def test_disable_toplevel_jsonapi
+            with_config(jsonapi_include_toplevel_object: false) do
+              hash = serialize(@post)
+              assert_nil(hash[:jsonapi])
+            end
+          end
+
+          def test_enable_toplevel_jsonapi
+            with_config(jsonapi_include_toplevel_object: true) do
+              hash = serialize(@post)
+              refute_nil(hash[:jsonapi])
+            end
+          end
+
+          def test_default_toplevel_jsonapi_version
+            with_config(jsonapi_include_toplevel_object: true) do
+              hash = serialize(@post)
+              assert_equal('1.0', hash[:jsonapi][:version])
+            end
+          end
+
+          def test_toplevel_jsonapi_no_meta
+            with_config(jsonapi_include_toplevel_object: true) do
+              hash = serialize(@post)
+              assert_nil(hash[:jsonapi][:meta])
+            end
+          end
+
+          def test_toplevel_jsonapi_meta
+            new_config = {
+              jsonapi_include_toplevel_object: true,
+              jsonapi_toplevel_meta: {
+                'copyright' => 'Copyright 2015 Example Corp.'
+              }
+            }
+            with_config(new_config) do
+              hash = serialize(@post)
+              assert_equal(new_config[:jsonapi_toplevel_meta], hash.fetch(:jsonapi).fetch(:meta))
+            end
+          end
+
+          private
+
+          def serialize(resource, options = {})
+            serializable(resource, { adapter: :json_api }.merge!(options)).serializable_hash
+          end
+        end
+      end
+    end
+  end
+end

test/support/serialization_testing.rb

@@ -1,4 +1,8 @@
 module SerializationTesting
+  def config
+    ActiveModel::Serializer.config
+  end
+
   private
 
   def generate_cached_serializer(obj)
@@ -18,6 +22,18 @@ module SerializationTesting
     ActiveModel::Serializer.config.adapter = old_adapter
   end
   alias_method :with_configured_adapter, :with_adapter
+
+  def with_config(hash)
+    old_config = config.dup
+    ActiveModel::Serializer.config.update(hash)
+    yield
+  ensure
+    ActiveModel::Serializer.config.replace(old_config)
+  end
+
+  def serializable(resource, options = {})
+    ActiveModel::SerializableResource.new(resource, options)
+  end
 end
 
 class Minitest::Test