Create RelatedEntity.fetch method

lib/diaspora_federation/entities/related_entity.rb

@@ -24,6 +24,18 @@ module DiasporaFederation
       #   @return [RelatedEntity] parent entity
       entity :parent, Entities::RelatedEntity, default: nil
 
+      # Get related entity from the backend or fetch it from remote if not available locally
+      # @return [RelatedEntity] fetched related entity
+      def self.fetch(author, type, guid)
+        # Try to fetch locally
+        entity = DiasporaFederation.callbacks.trigger(:fetch_related_entity, type, guid)
+        return entity if entity
+
+        # Fetch and receive entity from remote if not available locally
+        Federation::Fetcher.fetch_public(author, type, guid)
+        DiasporaFederation.callbacks.trigger(:fetch_related_entity, type, guid)
+      end
+
       # never add {RelatedEntity} to xml
       def to_xml
         nil

lib/diaspora_federation/entities/relayable.rb

@@ -193,13 +193,7 @@ module DiasporaFederation
             raise DiasporaFederation::Entity::ValidationError, "invalid #{self}! missing 'parent_guid'."
           }
 
-          data[:parent] = DiasporaFederation.callbacks.trigger(:fetch_related_entity, type, guid)
-
-          return if data[:parent]
-
-          # Fetch and receive parent from remote, if not available locally
-          Federation::Fetcher.fetch_public(data[:author], type, guid)
-          data[:parent] = DiasporaFederation.callbacks.trigger(:fetch_related_entity, type, guid)
+          data[:parent] = RelatedEntity.fetch(data[:author], type, guid)
         end
 
         def xml_parser_class

spec/lib/diaspora_federation/entities/related_entity_spec.rb

@@ -5,6 +5,26 @@ module DiasporaFederation
 
     it_behaves_like "an Entity subclass"
 
+    describe ".fetch" do
+      let(:guid) { Fabricate.sequence(:guid) }
+      let(:entity) { Fabricate(:related_entity) }
+
+      it "fetches the entity from the backend" do
+        expect_callback(:fetch_related_entity, "Entity", guid).and_return(entity)
+        expect(Federation::Fetcher).not_to receive(:fetch_public)
+
+        expect(described_class.fetch(entity.author, "Entity", guid)).to eq(entity)
+      end
+
+      it "fetches the entity from remote if not found on backend" do
+        expect_callback(:fetch_related_entity, "Entity", guid).ordered.and_return(nil)
+        expect(Federation::Fetcher).to receive(:fetch_public).ordered.with(entity.author, "Entity", guid)
+        expect_callback(:fetch_related_entity, "Entity", guid).ordered.and_return(entity)
+
+        expect(described_class.fetch(entity.author, "Entity", guid)).to eq(entity)
+      end
+    end
+
     describe "#to_xml" do
       it "returns nil" do
         expect(described_class.new(data).to_xml).to be_nil