Fix relayable import when parent is not fetchable

lib/archive_importer/entity_importer.rb

@@ -16,6 +16,7 @@ class ArchiveImporter
            DiasporaFederation::Discovery::InvalidDocument,
            DiasporaFederation::Discovery::DiscoveryError,
            DiasporaFederation::Federation::Fetcher::NotFetchable,
+           OwnRelayableImporter::NoParentError,
            ActiveRecord::RecordInvalid => e
       logger.warn "#{self}: #{e}"
       self.persisted_object = nil

lib/archive_importer/own_relayable_importer.rb

@@ -2,6 +2,8 @@
 
 class ArchiveImporter
   class OwnRelayableImporter < OwnEntityImporter
+    class NoParentError < RuntimeError; end
+
     def entity
       fetch_parent(symbolized_entity_data)
       entity_class.new(symbolized_entity_data)
@@ -19,6 +21,8 @@ class ArchiveImporter
         break entity_class::PARENT_TYPE if entity_class.const_defined?(:PARENT_TYPE)
       }
       entity = Diaspora::Federation::Mappings.model_class_for(type).find_by(guid: data.fetch(:parent_guid))
+      raise NoParentError if entity.nil?
+
       data[:parent] = Diaspora::Federation::Entities.related_entity(entity)
     end
   end

spec/lib/archive_importer/own_relayable_importer_spec.rb

@@ -28,4 +28,27 @@ describe ArchiveImporter::OwnRelayableImporter do
       ).to_json
     }
   end
+
+  context "with comment with unknown parent" do
+    let(:new_user) { FactoryBot.create(:user) }
+    let(:instance) { described_class.new(entity_json, new_user) }
+    let(:entity_json) { JSON.parse(<<~JSON) }
+      {
+        "entity_data" : {
+           "created_at" : "2015-10-19T13:58:16Z",
+           "guid" : "#{UUID.generate(:compact)}",
+           "text" : "test post",
+           "author" : "author@example.com",
+           "parent_guid": "#{UUID.generate(:compact)}"
+        },
+        "entity_type": "comment"
+      }
+    JSON
+
+    it "doesn't raise error" do
+      expect {
+        instance.import
+      }.not_to raise_error
+    end
+  end
 end