Fix #1759, Grape integration, adds serialization_context (#4)

* Fix #1759, Grape integration, adds serialization_context

- `serialization_context` is added in grape formatter so grape continues to render models without an explicit call to the `render` helper method
- Made it straightforward for subclasses to add other serializer options (such as `serialization_scope`).

* Updated Grape tests to include:
- paginated collections
- implicit Grape serializer (i.e. without explicit invocation of `render` helper method)

* Update Changelog with fixes.

test/grape_test.rb

@@ -1,6 +1,9 @@
 require 'test_helper'
 require 'grape'
 require 'grape/active_model_serializers'
+require 'kaminari'
+require 'kaminari/hooks'
+::Kaminari::Hooks.init
 
 class ActiveModelSerializers::GrapeTest < ActiveSupport::TestCase
   include Rack::Test::Methods
@@ -21,6 +24,30 @@ class ActiveModelSerializers::GrapeTest < ActiveSupport::TestCase
           ARModels::Post.all
         end
     end
+
+    def self.reset_all
+      ARModels::Post.delete_all
+      @all = nil
+    end
+
+    def self.collection_per
+      2
+    end
+
+    def self.collection
+      @collection ||=
+        begin
+          Kaminari.paginate_array(
+            [
+                  Profile.new(id: 1, name: 'Name 1', description: 'Description 1', comments: 'Comments 1'),
+                  Profile.new(id: 2, name: 'Name 2', description: 'Description 2', comments: 'Comments 2'),
+                  Profile.new(id: 3, name: 'Name 3', description: 'Description 3', comments: 'Comments 3'),
+                  Profile.new(id: 4, name: 'Name 4', description: 'Description 4', comments: 'Comments 4'),
+                  Profile.new(id: 5, name: 'Name 5', description: 'Description 5', comments: 'Comments 5')
+              ]
+          ).page(1).per(collection_per)
+        end
+    end
   end
 
   class GrapeTest < Grape::API
@@ -41,11 +68,28 @@ class ActiveModelSerializers::GrapeTest < ActiveSupport::TestCase
         posts = Models.all
         render posts, adapter: :json_api
       end
+
+      get '/render_collection_with_json_api' do
+        posts = Models.collection
+        render posts, adapter: :json_api
+      end
+
+      get '/render_with_implicit_formatter' do
+        Models.model1
+      end
+
+      get '/render_array_with_implicit_formatter' do
+        Models.all
+      end
+
+      get '/render_collection_with_implicit_formatter' do
+        Models.collection
+      end
     end
   end
 
   def app
-    GrapeTest.new
+    Grape::Middleware::Globals.new(GrapeTest.new)
   end
 
   def test_formatter_returns_json
@@ -77,6 +121,53 @@ class ActiveModelSerializers::GrapeTest < ActiveSupport::TestCase
     assert last_response.ok?
     assert_equal serializable_resource.to_json, last_response.body
   ensure
-    ARModels::Post.delete_all
+    Models.reset_all
+  end
+
+  def test_formatter_handles_collections
+    get '/grape/render_collection_with_json_api'
+    assert last_response.ok?
+
+    representation = JSON.parse(last_response.body)
+    assert representation.include?('data')
+    assert representation['data'].count == Models.collection_per
+    assert representation.include?('links')
+    assert representation['links'].count > 0
+  end
+
+  def test_implicit_formatter
+    ActiveModel::Serializer.config.adapter = :json_api
+    get '/grape/render_with_implicit_formatter'
+
+    post = Models.model1
+    serializable_resource = serializable(post, adapter: :json_api)
+
+    assert last_response.ok?
+    assert_equal serializable_resource.to_json, last_response.body
+  end
+
+  def test_implicit_formatter_handles_arrays
+    ActiveModel::Serializer.config.adapter = :json_api
+    get '/grape/render_array_with_implicit_formatter'
+
+    posts = Models.all
+    serializable_resource = serializable(posts, adapter: :json_api)
+
+    assert last_response.ok?
+    assert_equal serializable_resource.to_json, last_response.body
+  ensure
+    Models.reset_all
+  end
+
+  def test_implicit_formatter_handles_collections
+    ActiveModel::Serializer.config.adapter = :json_api
+    get '/grape/render_collection_with_implicit_formatter'
+    assert last_response.ok?
+
+    representation = JSON.parse(last_response.body)
+    assert representation.include?('data')
+    assert representation['data'].count == Models.collection_per
+    assert representation.include?('links')
+    assert representation['links'].count > 0
   end
 end