Fix posts from threads received out-of-order sometimes not being inserted into timelines (#27653)

spec/lib/activitypub/activity/create_spec.rb

@@ -23,6 +23,109 @@ RSpec.describe ActivityPub::Activity::Create do
     stub_request(:get, 'http://example.com/emojib.png').to_return(body: attachment_fixture('emojo.png'), headers: { 'Content-Type' => 'application/octet-stream' })
   end
 
+  describe 'processing posts received out of order' do
+    let(:follower) { Fabricate(:account, username: 'bob') }
+
+    let(:object_json) do
+      {
+        id: [ActivityPub::TagManager.instance.uri_for(sender), 'post1'].join('/'),
+        type: 'Note',
+        to: [
+          'https://www.w3.org/ns/activitystreams#Public',
+          ActivityPub::TagManager.instance.uri_for(follower),
+        ],
+        content: '@bob lorem ipsum',
+        published: 1.hour.ago.utc.iso8601,
+        updated: 1.hour.ago.utc.iso8601,
+        tag: {
+          type: 'Mention',
+          href: ActivityPub::TagManager.instance.uri_for(follower),
+        },
+      }
+    end
+
+    let(:reply_json) do
+      {
+        id: [ActivityPub::TagManager.instance.uri_for(sender), 'reply'].join('/'),
+        type: 'Note',
+        inReplyTo: object_json[:id],
+        to: [
+          'https://www.w3.org/ns/activitystreams#Public',
+          ActivityPub::TagManager.instance.uri_for(follower),
+        ],
+        content: '@bob lorem ipsum',
+        published: Time.now.utc.iso8601,
+        updated: Time.now.utc.iso8601,
+        tag: {
+          type: 'Mention',
+          href: ActivityPub::TagManager.instance.uri_for(follower),
+        },
+      }
+    end
+
+    def activity_for_object(json)
+      {
+        '@context': 'https://www.w3.org/ns/activitystreams',
+        id: [json[:id], 'activity'].join('/'),
+        type: 'Create',
+        actor: ActivityPub::TagManager.instance.uri_for(sender),
+        object: json,
+      }.with_indifferent_access
+    end
+
+    before do
+      follower.follow!(sender)
+    end
+
+    around do |example|
+      Sidekiq::Testing.fake! do
+        example.run
+        Sidekiq::Worker.clear_all
+      end
+    end
+
+    it 'correctly processes posts and inserts them in timelines', :aggregate_failures do
+      # Simulate a temporary failure preventing from fetching the parent post
+      stub_request(:get, object_json[:id]).to_return(status: 500)
+
+      # When receiving the reply…
+      described_class.new(activity_for_object(reply_json), sender, delivery: true).perform
+
+      # NOTE: Refering explicitly to the workers is a bit awkward
+      DistributionWorker.drain
+      FeedInsertWorker.drain
+
+      # …it creates a status with an unknown parent
+      reply = Status.find_by(uri: reply_json[:id])
+      expect(reply.reply?).to be true
+      expect(reply.in_reply_to_id).to be_nil
+
+      # …and creates a notification
+      expect(LocalNotificationWorker.jobs.size).to eq 1
+
+      # …but does not insert it into timelines
+      expect(redis.zscore(FeedManager.instance.key(:home, follower.id), reply.id)).to be_nil
+
+      # When receiving the parent…
+      described_class.new(activity_for_object(object_json), sender, delivery: true).perform
+
+      Sidekiq::Worker.drain_all
+
+      # …it creates a status and insert it into timelines
+      parent = Status.find_by(uri: object_json[:id])
+      expect(parent.reply?).to be false
+      expect(parent.in_reply_to_id).to be_nil
+      expect(reply.reload.in_reply_to_id).to eq parent.id
+
+      # Check that the both statuses have been inserted into the home feed
+      expect(redis.zscore(FeedManager.instance.key(:home, follower.id), parent.id)).to be_within(0.1).of(parent.id.to_f)
+      expect(redis.zscore(FeedManager.instance.key(:home, follower.id), reply.id)).to be_within(0.1).of(reply.id.to_f)
+
+      # Creates two notifications
+      expect(Notification.count).to eq 2
+    end
+  end
+
   describe '#perform' do
     context 'when fetching' do
       subject { described_class.new(json, sender) }