Fix poll expiration notification being re-triggered on implicit updates (#38078)

app/services/activitypub/process_status_update_service.rb

@@ -411,6 +411,11 @@ class ActivityPub::ProcessStatusUpdateService < BaseService
 
     return unless poll.present? && poll.expires_at.present? && poll.votes.exists?
 
+    # If the poll had previously expired, notifications should have already been sent out (or scheduled),
+    # and re-scheduling them would cause duplicate notifications for people who had already dismissed them
+    # (see #37948)
+    return if @previous_expires_at&.past?
+
     PollExpirationNotifyWorker.remove_from_scheduled(poll.id) if @previous_expires_at.present? && @previous_expires_at > poll.expires_at
     PollExpirationNotifyWorker.perform_at(poll.expires_at + 5.minutes, poll.id)
   end

spec/services/activitypub/process_status_update_service_spec.rb

@@ -136,6 +136,48 @@ RSpec.describe ActivityPub::ProcessStatusUpdateService do
       end
     end
 
+    context 'with an implicit update of a poll that has already expired' do
+      let(:account) { Fabricate(:account, domain: 'example.com') }
+      let!(:expiration) { 10.days.ago.utc }
+      let!(:status) do
+        Fabricate(:status,
+                  text: 'Hello world',
+                  account: account,
+                  poll_attributes: {
+                    options: %w(Foo Bar),
+                    account: account,
+                    multiple: false,
+                    hide_totals: false,
+                    expires_at: expiration,
+                  })
+      end
+
+      let(:payload) do
+        {
+          '@context': 'https://www.w3.org/ns/activitystreams',
+          id: 'https://example.com/foo',
+          type: 'Question',
+          content: 'Hello world',
+          endTime: expiration.iso8601,
+          oneOf: [
+            poll_option_json('Foo', 4),
+            poll_option_json('Bar', 3),
+          ],
+        }
+      end
+
+      before do
+        travel_to(expiration - 1.day) do
+          Fabricate(:poll_vote, poll: status.poll)
+        end
+      end
+
+      it 'does not re-trigger notifications' do
+        expect { subject.call(status, json, json) }
+          .to_not enqueue_sidekiq_job(PollExpirationNotifyWorker)
+      end
+    end
+
     context 'when the status changes a poll despite being not explicitly marked as updated' do
       let(:account) { Fabricate(:account, domain: 'example.com') }
       let!(:expiration) { 10.days.from_now.utc }