Invalidate reviews counter cache when MR gets closed/merged/reopened

Since the "Review requests for you" counter is cached and will
only invalidate after 20 minutes, we need to invalidate the
cache when MR gets closed/merged/reopened. Doing that, we will
be able to show accurate count on the dropdown when it happens.

app/services/merge_requests/close_service.rb

@@ -17,7 +17,7 @@ module MergeRequests
         notification_service.async.close_mr(merge_request, current_user)
         todo_service.close_merge_request(merge_request, current_user)
         execute_hooks(merge_request, 'close')
-        invalidate_cache_counts(merge_request, users: merge_request.assignees)
+        invalidate_cache_counts(merge_request, users: merge_request.assignees | merge_request.reviewers)
         merge_request.update_project_counter_caches
         cleanup_environments(merge_request)
         abort_auto_merge(merge_request, 'merge request was closed')

app/services/merge_requests/post_merge_service.rb

@@ -17,7 +17,7 @@ module MergeRequests
       create_note(merge_request)
       notification_service.merge_mr(merge_request, current_user)
       execute_hooks(merge_request, 'merge')
-      invalidate_cache_counts(merge_request, users: merge_request.assignees)
+      invalidate_cache_counts(merge_request, users: merge_request.assignees | merge_request.reviewers)
       merge_request.update_project_counter_caches
       delete_non_latest_diffs(merge_request)
       cancel_review_app_jobs!(merge_request)

app/services/merge_requests/reopen_service.rb

@@ -12,7 +12,7 @@ module MergeRequests
         execute_hooks(merge_request, 'reopen')
         merge_request.reload_diff(current_user)
         merge_request.mark_as_unchecked
-        invalidate_cache_counts(merge_request, users: merge_request.assignees)
+        invalidate_cache_counts(merge_request, users: merge_request.assignees | merge_request.reviewers)
         merge_request.update_project_counter_caches
         merge_request.cache_merge_request_closes_issues!(current_user)
         merge_request.cleanup_schedule&.destroy

changelogs/unreleased/296842-review-requests-counter-cache-invalidation.yml

+---
+title: Invalidate reviews counter cache when MR gets closed/merged/reopened
+merge_request: 51055
+author:
+type: fixed

spec/services/merge_requests/close_service_spec.rb

@@ -18,6 +18,7 @@ RSpec.describe MergeRequests::CloseService do
 
   describe '#execute' do
     it_behaves_like 'cache counters invalidator'
+    it_behaves_like 'merge request reviewers cache counters invalidator'
 
     context 'valid params' do
       let(:service) { described_class.new(project, user, {}) }

spec/services/merge_requests/post_merge_service_spec.rb

@@ -15,6 +15,7 @@ RSpec.describe MergeRequests::PostMergeService do
 
   describe '#execute' do
     it_behaves_like 'cache counters invalidator'
+    it_behaves_like 'merge request reviewers cache counters invalidator'
 
     it 'refreshes the number of open merge requests for a valid MR', :use_clean_rails_memory_store_caching do
       # Cache the counter before the MR changed state.

spec/services/merge_requests/reopen_service_spec.rb

@@ -17,6 +17,7 @@ RSpec.describe MergeRequests::ReopenService do
 
   describe '#execute' do
     it_behaves_like 'cache counters invalidator'
+    it_behaves_like 'merge request reviewers cache counters invalidator'
 
     context 'valid params' do
       let(:service) { described_class.new(project, user, {}) }

spec/support/shared_examples/services/merge_request_shared_examples.rb

@@ -58,3 +58,18 @@ RSpec.shared_examples 'reviewer_ids filter' do
     end
   end
 end
+
+RSpec.shared_examples 'merge request reviewers cache counters invalidator' do
+  let(:reviewer_1) { create(:user) }
+  let(:reviewer_2) { create(:user) }
+
+  before do
+    merge_request.update!(reviewers: [reviewer_1, reviewer_2])
+  end
+
+  it 'invalidates counter cache for reviewers' do
+    expect(merge_request.reviewers).to all(receive(:invalidate_merge_request_cache_counts))
+
+    described_class.new(project, user, {}).execute(merge_request)
+  end
+end