Federate deletion of collection item (#37837)

app/controllers/api/v1_alpha/collection_items_controller.rb

@@ -27,7 +27,7 @@ class Api::V1Alpha::CollectionItemsController < Api::BaseController
   def destroy
     authorize @collection, :update?
 
-    @collection_item.destroy
+    DeleteCollectionItemService.new.call(@collection_item)
 
     head 200
   end

app/serializers/activitypub/remove_featured_item_serializer.rb

@@ -0,0 +1,26 @@
+# frozen_string_literal: true
+
+class ActivityPub::RemoveFeaturedItemSerializer < ActivityPub::Serializer
+  include RoutingHelper
+
+  attributes :type, :actor, :target
+  has_one :object, serializer: ActivityPub::FeaturedItemSerializer
+
+  def type
+    'Remove'
+  end
+
+  def actor
+    ActivityPub::TagManager.instance.uri_for(collection.account)
+  end
+
+  def target
+    ActivityPub::TagManager.instance.uri_for(collection)
+  end
+
+  private
+
+  def collection
+    @collection ||= object.collection
+  end
+end

app/services/delete_collection_item_service.rb

@@ -0,0 +1,21 @@
+# frozen_string_literal: true
+
+class DeleteCollectionItemService
+  def call(collection_item)
+    @collection_item = collection_item
+    @collection = collection_item.collection
+    @collection_item.destroy!
+
+    distribute_remove_activity if Mastodon::Feature.collections_federation_enabled?
+  end
+
+  private
+
+  def distribute_remove_activity
+    ActivityPub::AccountRawDistributionWorker.perform_async(activity_json, @collection.account.id)
+  end
+
+  def activity_json
+    ActiveModelSerializers::SerializableResource.new(@collection_item, serializer: ActivityPub::RemoveFeaturedItemSerializer, adapter: ActivityPub::Adapter).to_json
+  end
+end

spec/serializers/activitypub/remove_featured_item_serializer_spec.rb

@@ -0,0 +1,27 @@
+# frozen_string_literal: true
+
+require 'rails_helper'
+
+RSpec.describe ActivityPub::RemoveFeaturedItemSerializer do
+  subject { serialized_record_json(object, described_class, adapter: ActivityPub::Adapter) }
+
+  let(:tag_manager) { ActivityPub::TagManager.instance }
+  let(:collection) { Fabricate(:collection) }
+  let(:object) { Fabricate(:collection_item, collection:) }
+
+  it 'serializes to the expected json' do
+    expect(subject).to include({
+      'type' => 'Remove',
+      'actor' => tag_manager.uri_for(collection.account),
+      'target' => tag_manager.uri_for(collection),
+      'object' => a_hash_including({
+        'type' => 'FeaturedItem',
+      }),
+    })
+
+    expect(subject).to_not have_key('id')
+    expect(subject).to_not have_key('published')
+    expect(subject).to_not have_key('to')
+    expect(subject).to_not have_key('cc')
+  end
+end

spec/services/delete_collection_item_service_spec.rb

@@ -0,0 +1,22 @@
+# frozen_string_literal: true
+
+require 'rails_helper'
+
+RSpec.describe DeleteCollectionItemService do
+  subject { described_class.new }
+
+  let(:collection_item) { Fabricate(:collection_item) }
+  let(:collection) { collection_item.collection }
+
+  describe '#call' do
+    it 'destroys the collection' do
+      expect { subject.call(collection_item) }.to change(collection.collection_items, :count).by(-1)
+    end
+
+    it 'federates a `Remove` activity', feature: :collections_federation do
+      subject.call(collection_item)
+
+      expect(ActivityPub::AccountRawDistributionWorker).to have_enqueued_sidekiq_job
+    end
+  end
+end