Add supports for :links and :data options to has_many associations for jsonapi adapter

lib/action_controller/serialization.rb

@@ -27,6 +27,7 @@ def get_serializer(resource, options = {})
       end
       ActiveModel::SerializableResource.serialize(resource, options) do |serializable_resource|
         if serializable_resource.serializer?
+          serializable_resource.url_helper = self
           serializable_resource.serialization_scope ||= serialization_scope
           serializable_resource.serialization_scope_name = _serialization_scope
           begin

lib/active_model/serializable_resource.rb

@@ -30,6 +30,10 @@ def serialization_scope=(scope)
       serializer_opts[:scope] = scope
     end
 
+    def url_helper=(url_helper)
+      adapter_opts[:url_helper] = url_helper
+    end
+
     def serialization_scope
       serializer_opts[:scope]
     end

lib/active_model/serializer/adapter/json_api.rb

@@ -8,14 +8,16 @@ class JsonApi < Adapter
         def initialize(serializer, options = {})
           super
           @hash = { data: [] }
-
+          @url_helper = options[:url_helper]
           if fields = options.delete(:fields)
             @fieldset = ActiveModel::Serializer::Fieldset.new(fields, serializer.json_key)
           else
             @fieldset = options[:fieldset]
           end
         end
 
+        attr_reader :url_helper
+
         def serializable_hash(options = nil)
           options ||= {}
           if serializer.respond_to?(:each)
@@ -44,10 +46,17 @@ def fragment_cache(cached_hash, non_cached_hash)
 
         private
 
-        def add_relationships(resource, name, serializers)
+        def add_relationships(resource, name, serializers, opts)
           resource[:relationships] ||= {}
-          resource[:relationships][name] ||= { data: [] }
-          resource[:relationships][name][:data] += serializers.map { |serializer| { type: serializer.json_api_type, id: serializer.id.to_s } }
+
+          if opts.fetch(:data, true)
+            resource[:relationships][name] ||= { data: [] }
+            resource[:relationships][name][:data] += serializers.map { |serializer| { type: serializer.json_api_type, id: serializer.id.to_s } }
+          end
+          if opts.fetch(:links, false)
+            resource[:relationships][name] ||= {}
+            resource[:relationships][name][:links] = { related: url_helper.url_for([serializer.object, name]) }
+          end
         end
 
         def add_relationship(resource, name, serializer, val=nil)
@@ -144,7 +153,7 @@ def add_resource_relationships(attrs, serializer, options = {})
             attrs[:relationships] ||= {}
 
             if serializer.respond_to?(:each)
-              add_relationships(attrs, key, serializer)
+              add_relationships(attrs, key, serializer, opts)
             else
               if opts[:virtual_value]
                 add_relationship(attrs, key, nil, opts[:virtual_value])

test/adapter/json_api/has_many_url_test.rb

@@ -0,0 +1,36 @@
+require 'test_helper'
+
+module ActionController
+  module Serialization
+    class JsonApiHasManyUrlTest < ActionController::TestCase
+      class MyController < ActionController::Base
+
+        def render_resource_with_url_association
+          @tag = Tag.new(id: 1)
+          @tag.posts = []
+          render json: @tag, adapter: :json_api, serializer: LinkTagSerializer
+        end
+      end
+
+      tests MyController
+
+      def test_render_resource_with_url_association
+        get :render_resource_with_url_association
+        expected = {
+          data: {
+            id: "1",
+            type: "tags",
+            relationships: {
+              posts: {
+                links: {
+                  related: "http://test.host/tags/1/posts"
+                }
+              }
+            }
+          }
+        }
+        assert_equal expected.to_json, response.body
+      end
+    end
+  end
+end

test/fixtures/poro.rb

@@ -1,10 +1,15 @@
 class Model
+  extend ActiveModel::Naming
   FILE_DIGEST = Digest::MD5.hexdigest(File.open(__FILE__).read)
 
   def self.model_name
     @_model_name ||= ActiveModel::Name.new(self)
   end
 
+  def to_model
+    self
+  end
+
   def initialize(hash={})
     @attributes = hash
   end
@@ -29,9 +34,14 @@ def id
     @attributes[:id] || @attributes['id'] || object_id
   end
 
+  def to_param
+    id.to_s
+  end
+
   ### Helper methods, not required to be serializable
   #
   # Convenience for adding @attributes readers and writers
+
   def method_missing(meth, *args)
     if meth.to_s =~ /^(.*)=$/
       @attributes[$1.to_sym] = args[0]
@@ -87,6 +97,7 @@ def cache_key
     "#{self.class.name.downcase}/#{self.id}"
   end
 end
+Tag = Class.new(Model)
 
 module Spam; end
 Spam::UnrelatedLink = Class.new(Model)
@@ -243,6 +254,10 @@ def self.root_name
   has_one :blog, key: :site
 end
 
+LinkTagSerializer = Class.new(ActiveModel::Serializer) do
+  has_many :posts, links: true, data: false
+end
+
 VirtualValueSerializer = Class.new(ActiveModel::Serializer) do
   attributes :id
 

test/test_helper.rb

@@ -86,6 +86,7 @@ class Foo < Rails::Application
 module TestHelper
   Routes = ActionDispatch::Routing::RouteSet.new
   Routes.draw do
+    get 'tags/:tag_id/posts', to: 'application#index', as: 'tag_posts'
     get ':controller(/:action(/:id))'
     get ':controller(/:action)'
   end