Support creating/updating polymorphic has-many relationships

Author: saravanak

lib/jsonapi/request_parser.rb

@@ -521,19 +521,15 @@ def parse_to_many_relationship(link_value, relationship, &add_result)
 
       links_object = parse_to_many_links_object(linkage)
 
-      # Since we do not yet support polymorphic to_many relationships we will raise an error if the type does not match the
-      # relationship's type.
-      # ToDo: Support Polymorphic relationships
-
       if links_object.length == 0
         add_result.call([])
       else
-        if links_object.length > 1 || !links_object.has_key?(unformat_key(relationship.type).to_s)
-          fail JSONAPI::Exceptions::TypeMismatch.new(links_object[:type])
-        end
-
+        defined_relationship_resource = Resource.resource_for(@resource_klass.module_path + unformat_key(relationship.type).to_s)
         links_object.each_pair do |type, keys|
           relationship_resource = Resource.resource_for(@resource_klass.module_path + unformat_key(type).to_s)
+          if !relationship_resource.ancestors.include?(defined_relationship_resource)
+            fail JSONAPI::Exceptions::TypeMismatch.new(links_object[:type])
+          end
           add_result.call relationship_resource.verify_keys(keys, @context)
         end
       end

test/integration/requests/request_test.rb

@@ -211,6 +211,52 @@ def test_post_single
     assert_jsonapi_response 201
   end
 
+  def test_post_polymorphic
+    post '/people', params:
+      {
+        'data' => {
+          'type' => 'people',
+          'attributes' => {
+            'name' => 'Reo',
+            'email' => 'reo@xyz.fake',
+            'date_joined' => 'Thu, 01 Jan 2019 00:00:00 UTC +00:00',
+          },
+          'relationships' => {
+            'vehicles' => {'data' => [{'type' => 'car', 'id' => '1'}]},
+          }
+        }
+      }.to_json,
+      headers: {
+        'CONTENT_TYPE' => JSONAPI::MEDIA_TYPE,
+        'Accept' => JSONAPI::MEDIA_TYPE
+      }
+
+    assert_jsonapi_response 201
+  end
+
+  def test_post_polymorphic_invalid
+    post '/people', params:
+      {
+        'data' => {
+          'type' => 'people',
+          'attributes' => {
+            'name' => 'Reo',
+            'email' => 'reo@xyz.fake',
+            'date_joined' => 'Thu, 01 Jan 2019 00:00:00 UTC +00:00',
+          },
+          'relationships' => {
+            'vehicles' => {'data' => [{'type' => 'author', 'id' => '1'}]},
+          }
+        }
+      }.to_json,
+      headers: {
+        'CONTENT_TYPE' => JSONAPI::MEDIA_TYPE,
+        'Accept' => JSONAPI::MEDIA_TYPE
+      }
+
+    assert_jsonapi_response 400, msg: "Submitting a thing as a vehicle should raise a type mismatch error"
+  end
+
   def test_post_single_missing_data_contents
     post '/posts', params:
          {