Remove todos for users from removed linked group

When a ProjectGroupLink is being removed from a private project,
we should be checking if there are any todos for users from linked group
and cleanup those.

Public projects visibility change or features(issues, merge requests)
permission changes are already being handled in Projects::UpdateService

app/services/projects/group_links/destroy_service.rb

@@ -6,6 +6,12 @@ module Projects
       def execute(group_link)
         return false unless group_link
 
+        if group_link.project.private?
+          TodosDestroyer::ProjectPrivateWorker.perform_in(Todo::WAIT_FOR_DELETE, project.id)
+        else
+          TodosDestroyer::ConfidentialIssueWorker.perform_in(Todo::WAIT_FOR_DELETE, nil, project.id)
+        end
+
         group_link.destroy
       end
     end

changelogs/unreleased/security-35235-todos-cleanup.yml

+---
+title: Cleanup todos for users from a removed linked group
+merge_request:
+author:
+type: security

spec/services/projects/group_links/destroy_service_spec.rb

@@ -3,8 +3,8 @@
 require 'spec_helper'
 
 describe Projects::GroupLinks::DestroyService, '#execute' do
-  let(:group_link) { create :project_group_link }
-  let(:project) { group_link.project }
+  let(:project) { create(:project, :private) }
+  let!(:group_link) { create(:project_group_link, project: project) }
   let(:user) { create :user }
   let(:subject) { described_class.new(project, user) }
 
@@ -15,4 +15,39 @@ describe Projects::GroupLinks::DestroyService, '#execute' do
   it 'returns false if group_link is blank' do
     expect { subject.execute(nil) }.not_to change { project.project_group_links.count }
   end
+
+  describe 'todos cleanup' do
+    context 'when project is private' do
+      it 'triggers todos cleanup' do
+        expect(TodosDestroyer::ProjectPrivateWorker).to receive(:perform_in).with(Todo::WAIT_FOR_DELETE, project.id)
+        expect(project.private?).to be true
+
+        subject.execute(group_link)
+      end
+    end
+
+    context 'when project is public or internal' do
+      shared_examples_for 'removes confidential todos' do
+        it 'does not trigger todos cleanup' do
+          expect(TodosDestroyer::ProjectPrivateWorker).not_to receive(:perform_in).with(Todo::WAIT_FOR_DELETE, project.id)
+          expect(TodosDestroyer::ConfidentialIssueWorker).to receive(:perform_in).with(Todo::WAIT_FOR_DELETE, nil, project.id)
+          expect(project.private?).to be false
+
+          subject.execute(group_link)
+        end
+      end
+
+      context 'when project is public' do
+        let(:project) { create(:project, :public) }
+
+        it_behaves_like 'removes confidential todos'
+      end
+
+      context 'when project is internal' do
+        let(:project) { create(:project, :public) }
+
+        it_behaves_like 'removes confidential todos'
+      end
+    end
+  end
 end