WIP: make belongs_to polymorphic use id_method_name

lib/fast_jsonapi/relationship.rb

@@ -68,6 +68,13 @@ def ids_hash_from_record_and_relationship(record, params = {})
 
       return unless associated_object = fetch_associated_object(record, params)
 
+      if relationship_type == :belongs_to
+        return {
+          id: fetch_id(record, params),
+          type: run_key_transform(associated_object.class.name.demodulize.underscore)
+        }
+      end
+
       return associated_object.map do |object|
         id_hash_from_record object, polymorphic
       end if associated_object.respond_to? :map

spec/lib/object_serializer_polymorphic_spec.rb

@@ -1,8 +1,12 @@
 require 'spec_helper'
 
 describe FastJsonapi::ObjectSerializer do
+  class ListOwner
+    attr_accessor :id, :uuid
+  end
+
   class List
-    attr_accessor :id, :name, :items
+    attr_accessor :id, :name, :items, :owner, :owner_id, :owner_type, :owner_uuid
   end
 
   class ChecklistItem
@@ -19,6 +23,13 @@ class ListSerializer
     attributes :name
     set_key_transform :dash
     has_many :items, polymorphic: true
+    belongs_to :owner, polymorphic: true, id_method_name: :owner_uuid
+    belongs_to :owner_block, polymorphic: true, id_method_name: :uuid do
+      owner = ListOwner.new
+      owner.id = 2
+      owner.uuid = 234234234
+      owner
+    end
   end
 
   let(:car) do
@@ -36,6 +47,13 @@ class ListSerializer
     checklist_item
   end
 
+  let(:owner) do
+    owner = ListOwner.new
+    owner.id = 1
+    owner.uuid = 123123123
+    owner
+  end
+
   context 'when serializing id and type of polymorphic relationships' do
     it 'should return correct type when transform_method is specified' do
       list = List.new
@@ -47,5 +65,33 @@ class ListSerializer
       record_type = list_hash[:data][:relationships][:items][:data][1][:type]
       expect(record_type).to eq 'car'.to_sym
     end
+
+    it 'should return correct id for belongs_to when id_method_name is specified' do
+      list = List.new
+      list.id = 1
+      list.owner = owner
+      list.owner_id = owner.id
+      list.owner_type = owner.class.name
+      list.owner_uuid = owner.uuid
+      list_hash = ListSerializer.new(list).to_hash
+      record_uuid = list_hash[:data][:relationships][:owner][:data][:id]
+      expect(record_uuid).to eq list.owner_uuid
+    end
+
+    it 'should return nil for belongs_to when association is nil' do
+      list = List.new
+      list.id = 1
+      list_hash = ListSerializer.new(list).to_hash
+      owner_relationship = list_hash[:data][:relationships][:owner][:data]
+      expect(owner_relationship).to be_nil
+    end
+
+    it 'should return correct data for belongs_to with object_block when id_method_name is specified' do
+      list = List.new
+      list.id = 1
+      list_hash = ListSerializer.new(list).to_hash
+      owner_relationship = list_hash[:data][:relationships][:'owner-block'][:data]
+      expect(owner_relationship).to eq(id: 234234234, type: :'list-owner')
+    end
   end
 end