Reject existing Follow in addition to sending a Block (#9811)

Mastodon expects remote servers to remove follow relationships upon receiving
a Block. However, the spec only evokes Block activities in a C2S context, never
in a S2S context.

This PR, in addition to federating the Block, explicitly sends a Reject for any
affected follow relationship, which makes a bit more sense with regards to the
spec.

1 files changed, 15 insertions, 0 deletions

diff --git a/app/services/unfollow_service.rb b/app/services/unfollow_service.rb
index 03e45912d..95da2a667 100644
--- a/app/services/unfollow_service.rb
+++ b/app/services/unfollow_service.rb
@@ -20,6 +20,7 @@ class UnfollowService < BaseService
 
     follow.destroy!
     create_notification(follow) unless @target_account.local?
+    create_reject_notification(follow) if @target_account.local? && !@source_account.local?
     UnmergeWorker.perform_async(@target_account.id, @source_account.id)
     follow
   end
@@ -42,6 +43,12 @@ class UnfollowService < BaseService
     end
   end
 
+  def create_reject_notification(follow)
+    # Rejecting an already-existing follow request
+    return unless follow.account.activitypub?
+    ActivityPub::DeliveryWorker.perform_async(build_reject_json(follow), follow.target_account_id, follow.account.inbox_url)
+  end
+
   def build_json(follow)
     ActiveModelSerializers::SerializableResource.new(
       follow,
@@ -50,6 +57,14 @@ class UnfollowService < BaseService
     ).to_json
   end
 
+  def build_reject_json(follow)
+    ActiveModelSerializers::SerializableResource.new(
+      follow,
+      serializer: ActivityPub::RejectFollowSerializer,
+      adapter: ActivityPub::Adapter
+    ).to_json
+  end
+
   def build_xml(follow)
     OStatus::AtomSerializer.render(OStatus::AtomSerializer.new.unfollow_salmon(follow))
   end