adds polymorphic option to association definition which includes asso…

CHANGELOG.md

@@ -16,6 +16,7 @@ Features:
 
 Fixes:
 - [#1700](https://github.com/rails-api/active_model_serializers/pull/1700) Support pagination link for Kaminari when no data is returned. (@iamnader)
+- [#1726](https://github.com/rails-api/active_model_serializers/pull/1726) Adds polymorphic option to association definition which includes association type/nesting in serializer (@cgmckeever)
 
 Misc:
 - [#1673](https://github.com/rails-api/active_model_serializers/pull/1673) Adds "How to" guide on using AMS with POROs (@DrSayre)

docs/general/serializers.md

@@ -52,6 +52,7 @@ Where:
   - `if:`
   - `unless:`
   - `virtual_value:`
+  - `polymorphic:` defines if polymorphic relation type should be nested in serialized association.
 - optional: `&block` is a context that returns the association's attributes.
   - prevents `association_name` method from being called.
   - return value of block is used as the association value.

lib/active_model_serializers/adapter/attributes.rb

@@ -45,7 +45,14 @@ def relationship_value_for(association, options)
         return unless association.serializer && association.serializer.object
 
         opts = instance_options.merge(include: @include_tree[association.key])
-        Attributes.new(association.serializer, opts).serializable_hash(options)
+        relationship_value = Attributes.new(association.serializer, opts).serializable_hash(options)
+
+        if association.options[:polymorphic] && relationship_value
+          polymorphic_type = association.serializer.object.class.name.underscore
+          relationship_value = { type: polymorphic_type, polymorphic_type.to_sym => relationship_value }
+        end
+
+        relationship_value
       end
 
       # Set @cached_attributes

test/adapter/polymorphic_test.rb

@@ -8,10 +8,17 @@ class PolymorphicTest < ActiveSupport::TestCase
           @employee = Employee.new(id: 42, name: 'Zoop Zoopler', email: 'zoop@example.com')
           @picture = @employee.pictures.new(id: 1, title: 'headshot-1.jpg')
           @picture.imageable = @employee
+        end
+
+        def serialization(resource, adapter = :attributes)
+          serializable(resource, adapter: adapter, serializer: PolymorphicBelongsToSerializer).as_json
+        end
 
-          @attributes_serialization = serializable(@picture, serializer: PolymorphicBelongsToSerializer) # uses default adapter: attributes
-          @json_serialization = serializable(@picture, adapter: :json, serializer: PolymorphicBelongsToSerializer)
-          @json_api_serialization = serializable(@picture, adapter: :json_api, serializer: PolymorphicBelongsToSerializer)
+        def tag_serialization(adapter = :attributes)
+          tag = PolyTag.new(id: 1, phrase: 'foo')
+          tag.object_tags << ObjectTag.new(id: 1, poly_tag_id: 1, taggable: @employee)
+          tag.object_tags << ObjectTag.new(id: 5, poly_tag_id: 1, taggable: @picture)
+          serializable(tag, adapter: adapter, serializer: PolymorphicTagSerializer, include: '*.*').as_json
         end
 
         def test_attributes_serialization
@@ -20,31 +27,123 @@ def test_attributes_serialization
               id: 1,
               title: 'headshot-1.jpg',
               imageable: {
-                id: 42,
-                name: 'Zoop Zoopler'
+                  type: 'employee',
+                  employee: {
+                    id: 42,
+                    name: 'Zoop Zoopler'
+                  }
               }
             }
 
-          assert_equal(expected, @attributes_serialization.as_json)
+          assert_equal(expected, serialization(@picture))
         end
 
-        def test_json_serializer
+        def test_attributes_serialization_without_polymorphic_association
+          expected =
+            {
+              id: 2,
+              title: 'headshot-2.jpg',
+              imageable: nil
+            }
+
+          simple_picture = Picture.new(id: 2, title: 'headshot-2.jpg')
+          assert_equal(expected, serialization(simple_picture))
+        end
+
+        def test_attributes_serialization_with_polymorphic_has_many
+          expected =
+            {
+              id: 1,
+              phrase: 'foo',
+              object_tags: [
+                {
+                  id: 1,
+                  taggable: {
+                    type: 'employee',
+                    employee: {
+                      id: 42
+                    }
+                  }
+                },
+                {
+                  id: 5,
+                  taggable: {
+                    type: 'picture',
+                    picture: {
+                      id: 1
+                    }
+                  }
+                }
+              ]
+            }
+          assert_equal(expected, tag_serialization)
+        end
+
+        def test_json_serialization
           expected =
             {
               picture: {
                 id: 1,
                 title: 'headshot-1.jpg',
                 imageable: {
-                  id: 42,
-                  name: 'Zoop Zoopler'
+                  type: 'employee',
+                  employee: {
+                    id: 42,
+                    name: 'Zoop Zoopler'
+                  }
                 }
               }
             }
 
-          assert_equal(expected, @json_serialization.as_json)
+          assert_equal(expected, serialization(@picture, :json))
+        end
+
+        def test_json_serialization_without_polymorphic_association
+          expected =
+            {
+              picture: {
+                id: 2,
+                title: 'headshot-2.jpg',
+                imageable: nil
+              }
+            }
+
+          simple_picture = Picture.new(id: 2, title: 'headshot-2.jpg')
+          assert_equal(expected, serialization(simple_picture, :json))
+        end
+
+        def test_json_serialization_with_polymorphic_has_many
+          expected =
+            {
+              poly_tag: {
+                id: 1,
+                phrase: 'foo',
+                object_tags: [
+                  {
+                    id: 1,
+                    taggable: {
+                      type: 'employee',
+                      employee: {
+                        id: 42
+                      }
+                    }
+                  },
+                  {
+                    id: 5,
+                    taggable: {
+                      type: 'picture',
+                      picture: {
+                        id: 1
+                      }
+                    }
+                  }
+                ]
+              }
+            }
+          assert_equal(expected, tag_serialization(:json))
         end
 
-        def test_json_api_serializer
+        def test_json_api_serialization
           expected =
             {
               data: {
@@ -64,7 +163,7 @@ def test_json_api_serializer
               }
             }
 
-          assert_equal(expected, @json_api_serialization.as_json)
+          assert_equal(expected, serialization(@picture, :json_api))
         end
       end
     end

test/fixtures/active_record.rb

@@ -24,6 +24,16 @@
     t.string :email
     t.timestamp null: false
   end
+  create_table :object_tags, force: true do |t|
+    t.string :poly_tag_id
+    t.string :taggable_type
+    t.string :taggable_id
+    t.timestamp null: false
+  end
+  create_table :poly_tags, force: true do |t|
+    t.string :phrase
+    t.timestamp null: false
+  end
   create_table :pictures, force: true do |t|
     t.string :title
     t.string :imageable_type

test/fixtures/poro.rb

@@ -70,10 +70,21 @@ def cache_key
 
 class Employee < ActiveRecord::Base
   has_many :pictures, as: :imageable
+  has_many :object_tags, as: :taggable
+end
+
+class ObjectTag < ActiveRecord::Base
+  belongs_to :poly_tag
+  belongs_to :taggable, polymorphic: true
 end
 
 class Picture < ActiveRecord::Base
   belongs_to :imageable, polymorphic: true
+  has_many :object_tags, as: :taggable
+end
+
+class PolyTag < ActiveRecord::Base
+  has_many :object_tags
 end
 
 module Spam; end
@@ -245,7 +256,23 @@ def maker
 PolymorphicBelongsToSerializer = Class.new(ActiveModel::Serializer) do
   attributes :id, :title
 
-  has_one :imageable, serializer: PolymorphicHasManySerializer
+  has_one :imageable, serializer: PolymorphicHasManySerializer, polymorphic: true
+end
+
+PolymorphicSimpleSerializer = Class.new(ActiveModel::Serializer) do
+  attributes :id
+end
+
+PolymorphicObjectTagSerializer = Class.new(ActiveModel::Serializer) do
+  attributes :id
+
+  has_many :taggable, serializer: PolymorphicSimpleSerializer, polymorphic: true
+end
+
+PolymorphicTagSerializer = Class.new(ActiveModel::Serializer) do
+  attributes :id, :phrase
+
+  has_many :object_tags, serializer: PolymorphicObjectTagSerializer
 end
 
 Spam::UnrelatedLinkSerializer = Class.new(ActiveModel::Serializer) do