Merge 3e4c82f2066bb789b0399de878872ee39f63c9ed into 7db80f673d037ed841bef8e8a93dcda21380e135

lib/fast_jsonapi/serialization_core.rb

@@ -53,9 +53,10 @@ module FastJsonapi
 
       def relationships_hash(record, relationships = nil, fieldset = nil, includes_list = nil, params = {})
         relationships = relationships_to_serialize if relationships.nil?
-        relationships = relationships.slice(*fieldset) if fieldset.present?
+        relationship_fieldset = fieldset.present? ? fieldset & relationships.keys : []
-        relationships = {} if fieldset == []
+        return nil if fieldset.present? && relationship_fieldset.empty?
 
+        relationships = relationships.slice(*relationship_fieldset) if fieldset.present?
         relationships.each_with_object({}) do |(key, relationship), hash|
           included = includes_list.present? && includes_list.include?(key)
           relationship.serialize(record, included, params, hash)
@@ -72,15 +73,15 @@ module FastJsonapi
           record_hash = cache_store_instance.fetch(record, **cache_opts) do
             temp_hash = id_hash(id_from_record(record, params), record_type, true)
             temp_hash[:attributes] = attributes_hash(record, fieldset, params) if attributes_to_serialize.present?
-            temp_hash[:relationships] = relationships_hash(record, cachable_relationships_to_serialize, fieldset, includes_list, params) if cachable_relationships_to_serialize.present?
+            temp_hash[:relationships] = relationships_hash(record, cachable_relationships_to_serialize, fieldset, includes_list, params) if cachable_relationships_to_serialize.present? && relationships_hash(record, cachable_relationships_to_serialize, fieldset, includes_list, params).present?
             temp_hash[:links] = links_hash(record, params) if data_links.present?
             temp_hash
           end
-          record_hash[:relationships] = (record_hash[:relationships] || {}).merge(relationships_hash(record, uncachable_relationships_to_serialize, fieldset, includes_list, params)) if uncachable_relationships_to_serialize.present?
+          record_hash[:relationships] = (record_hash[:relationships] || {}).merge(relationships_hash(record, uncachable_relationships_to_serialize, fieldset, includes_list, params)) if uncachable_relationships_to_serialize.present? && relationships_hash(record, nil, fieldset, includes_list, params).present?
         else
           record_hash = id_hash(id_from_record(record, params), record_type, true)
           record_hash[:attributes] = attributes_hash(record, fieldset, params) if attributes_to_serialize.present?
-          record_hash[:relationships] = relationships_hash(record, nil, fieldset, includes_list, params) if relationships_to_serialize.present?
+          record_hash[:relationships] = relationships_hash(record, nil, fieldset, includes_list, params) if relationships_to_serialize.present? && relationships_hash(record, nil, fieldset, includes_list, params).present?
           record_hash[:links] = links_hash(record, params) if data_links.present?
         end
 

spec/integration/attributes_fields_spec.rb

@@ -57,6 +57,29 @@ RSpec.describe JSONAPI::Serializer do
           .and(have_id(actor.movies[0].id))
           .and(have_jsonapi_attributes('release_year').exactly)
         )
+        expect(serialized['data'])
+        .to_not have_relationship('played_movies')
+      end
+    end
+
+    context 'with fields for the relationship' do
+      let(:params) do
+        {
+          fields: { actor: [:first_name, :played_movies] }
+        }
+      end
+
+      it do
+        expect(serialized['data'])
+          .to have_jsonapi_attributes(:first_name).exactly
+
+        expect(serialized['data'])
+        .to have_relationship('played_movies')
+        .with_data(
+          [
+            { 'id' => actor.movies[0].id, 'type' => 'movie' },
+          ]
+        )
       end
     end
   end