fix some more edge cases

lib/gitlab/import_export/relation_factory.rb

@@ -80,8 +80,7 @@ module Gitlab
         case @relation_name
         when :merge_request_diff_files       then setup_diff
         when :notes                          then setup_note
-        when :milestone, :milestones,
-          :project_label, :project_labels then setup_project_group
+        when *(EXISTING_OBJECT_CHECK - [:project_feature])  then setup_project_group
         when 'Ci::Pipeline'                  then setup_pipeline
         else
           @relation_hash['project_id'] = @project.id
@@ -275,7 +274,11 @@ module Gitlab
       end
 
       def find_or_create_object!
-        finder_hash = parsed_relation_hash.slice('title', 'project_id', 'group_id')
+        # Can't use IDs as validation exists calilng `.group` or `.project`
+        finder_hash = { project: @project }.tap do |hash|
+          hash[:group] = @project.group if relation_class.attribute_method?('group_id')
+          hash[:title] = parsed_relation_hash['title'] if parsed_relation_hash['title']
+        end
 
         if label?
           label = GroupProjectFinder.find_or_new(Label, finder_hash)
@@ -288,8 +291,10 @@ module Gitlab
           object = GroupProjectFinder.find_or_create(relation_class, finder_hash)
 
           if milestone?
-            parsed_relation_hash.delete('group_id') if object.project_id
-            parsed_relation_hash.delete('project_id') if object.group_id
+            parsed_relation_hash.delete('group_id') if object.project
+            parsed_relation_hash.delete('project_id') if object.group
+            parsed_relation_hash.delete('iid')
+            parsed_relation_hash.delete('id')
           end
 
           object

spec/lib/gitlab/import_export/project_tree_restorer_spec.rb

@@ -246,13 +246,6 @@ describe Gitlab::ImportExport::ProjectTreeRestorer do
       expect(project.issues.size).to eq(results.fetch(:issues, 0))
     end
 
-    it 'has issue with group label and project label' do
-      labels = project.issues.first.labels
-
-      expect(labels.where(type: "ProjectLabel").count).to eq(results.fetch(:first_issue_labels, 0))
-      expect(labels.where(type: "ProjectLabel").where.not(group_id: nil).count).to eq(0)
-    end
-
     it 'does not set params that are excluded from import_export settings' do
       expect(project.import_type).to be_nil
       expect(project.creator_id).not_to eq 123
@@ -268,12 +261,6 @@ describe Gitlab::ImportExport::ProjectTreeRestorer do
     it 'has group milestone' do
       expect(project.group.milestones.size).to eq(results.fetch(:milestones, 0))
     end
-
-    it 'has issue with group label' do
-      labels = project.issues.first.labels
-
-      expect(labels.where(type: "GroupLabel").count).to eq(results.fetch(:first_issue_labels, 0))
-    end
   end
 
   context 'Light JSON' do
@@ -360,12 +347,12 @@ describe Gitlab::ImportExport::ProjectTreeRestorer do
       it_behaves_like 'restores project correctly',
                       issues: 2,
                       labels: 1,
-                      milestones: 1,
+                      milestones: 2,
                       first_issue_labels: 1
 
       it_behaves_like 'restores group correctly',
-                      labels: 1,
-                      milestones: 1,
+                      labels: 0,
+                      milestones: 0,
                       first_issue_labels: 1
     end