Reset todo counters when the target is deleted

When the target is deleted, todos are destroyed, but we did not reset the todo
cache for users with todos on the deleted target. This would only update after
the next time the todo cache was updated for that user.

app/controllers/concerns/issuable_actions.rb

@@ -55,7 +55,6 @@ module IssuableActions
   def destroy
     Issuable::DestroyService.new(issuable.project, current_user).execute(issuable)
-    TodoService.new.destroy_issuable(issuable, current_user)
     name = issuable.human_class_name
     flash[:notice] = "The #{name} was successfully deleted."

app/services/issuable/destroy_service.rb

 module Issuable
   class DestroyService < IssuableBaseService
     def execute(issuable)
-      if issuable.destroy
-        issuable.update_project_counter_caches
+      TodoService.new.destroy_target(issuable) do |issuable|
+        if issuable.destroy
+          issuable.update_project_counter_caches
+        end
       end
     end
   end

app/services/notes/destroy_service.rb

 module Notes
   class DestroyService < BaseService
     def execute(note)
-      note.destroy
+      TodoService.new.destroy_target(note) do |note|
+        note.destroy
+      end
     end
   end
 end

app/services/todo_service.rb

@@ -31,12 +31,20 @@ class TodoService
     mark_pending_todos_as_done(issue, current_user)
   end
-  # When we destroy an issuable we should:
+  # When we destroy a todo target we should:
   #
-  #  * refresh the todos count cache for the current user
+  #  * refresh the todos count cache for all users with todos on the target
   #
-  def destroy_issuable(issuable, user)
-    user.update_todos_count_cache
+  # This needs to yield back to the caller to destroy the target, because it
+  # collects the todo users before the todos themselves are deleted, then
+  # updates the todo counts for those users.
+  #
+  def destroy_target(target)
+    todo_users = User.where(id: target.todos.pending.select(:user_id)).to_a
+
+    yield target
+
+    todo_users.each(&:update_todos_count_cache)
   end
   # When we reassign an issue we should:

changelogs/unreleased/40871-todo-notification-count-shows-notification-without-having-a-todo.yml

+---
+title: Reset todo counters when the target is deleted
+merge_request: 15807
+author:
+type: fixed

spec/controllers/projects/issues_controller_spec.rb

@@ -861,7 +861,7 @@ describe Projects::IssuesController do
       end
       it 'delegates the update of the todos count cache to TodoService' do
-        expect_any_instance_of(TodoService).to receive(:destroy_issuable).with(issue, owner).once
+        expect_any_instance_of(TodoService).to receive(:destroy_target).with(issue).once
         delete :destroy, namespace_id: project.namespace, project_id: project, id: issue.iid
       end

spec/controllers/projects/merge_requests_controller_spec.rb

@@ -468,7 +468,7 @@ describe Projects::MergeRequestsController do
       end
       it 'delegates the update of the todos count cache to TodoService' do
-        expect_any_instance_of(TodoService).to receive(:destroy_issuable).with(merge_request, owner).once
+        expect_any_instance_of(TodoService).to receive(:destroy_target).with(merge_request).once
         delete :destroy, namespace_id: project.namespace, project_id: project, id: merge_request.iid
       end

spec/services/issuable/destroy_service_spec.rb

@@ -2,7 +2,7 @@ require 'spec_helper'
 describe Issuable::DestroyService do
   let(:user) { create(:user) }
-  let(:project) { create(:project) }
+  let(:project) { create(:project, :public) }
   subject(:service) { described_class.new(project, user) }
@@ -19,6 +19,13 @@ describe Issuable::DestroyService do
         service.execute(issue)
       end
+
+      it 'updates the todo caches for users with todos on the issue' do
+        create(:todo, target: issue, user: user, author: user, project: project)
+
+        expect { service.execute(issue) }
+          .to change { user.todos_pending_count }.from(1).to(0)
+      end
     end
     context 'when issuable is a merge request' do
@@ -33,6 +40,13 @@ describe Issuable::DestroyService do
         service.execute(merge_request)
       end
+
+      it 'updates the todo caches for users with todos on the merge request' do
+        create(:todo, target: merge_request, user: user, author: user, project: project)
+
+        expect { service.execute(merge_request) }
+          .to change { user.todos_pending_count }.from(1).to(0)
+      end
     end
   end
 end

spec/services/notes/destroy_service_spec.rb

 require 'spec_helper'
 describe Notes::DestroyService do
+  set(:project) { create(:project, :public) }
+  set(:issue) { create(:issue, project: project) }
+  let(:user) { issue.author }
+
   describe '#execute' do
     it 'deletes a note' do
-      project = create(:project)
-      issue = create(:issue, project: project)
       note = create(:note, project: project, noteable: issue)
-      described_class.new(project, note.author).execute(note)
+      described_class.new(project, user).execute(note)
       expect(project.issues.find(issue.id).notes).not_to include(note)
     end
+
+    it 'updates the todo counts for users with todos for the note' do
+      note = create(:note, project: project, noteable: issue)
+      create(:todo, note: note, target: issue, user: user, author: user, project: project)
+
+      expect { described_class.new(project, user).execute(note) }
+        .to change { user.todos_pending_count }.from(1).to(0)
+    end
   end
 end

spec/services/todo_service_spec.rb

@@ -248,11 +248,26 @@ describe TodoService do
       end
     end
-    describe '#destroy_issuable' do
-      it 'refresh the todos count cache for the user' do
-        expect(john_doe).to receive(:update_todos_count_cache).and_call_original
-        service.destroy_issuable(issue, john_doe)
+    describe '#destroy_target' do
+      it 'refreshes the todos count cache for users with todos on the target' do
+        create(:todo, target: issue, user: john_doe, author: john_doe, project: issue.project)
+        expect_any_instance_of(User).to receive(:update_todos_count_cache).and_call_original
+
+        service.destroy_target(issue) { }
+      end
+
+      it 'does not refresh the todos count cache for users with only done todos on the target' do
+        create(:todo, :done, target: issue, user: john_doe, author: john_doe, project: issue.project)
+
+        expect_any_instance_of(User).not_to receive(:update_todos_count_cache)
+
+        service.destroy_target(issue) { }
+      end
+
+      it 'yields the target to the caller' do
+        expect { |b| service.destroy_target(issue, &b) }
+          .to yield_with_args(issue)
       end
     end