Send and handle "Delete" activity for deleted users

lib/pleroma/web/activity_pub/transmogrifier.ex

@@ -641,7 +641,7 @@ defmodule Pleroma.Web.ActivityPub.Transmogrifier do
   # an error or a tombstone.  This would allow us to verify that a deletion actually took
   # place.
   def handle_incoming(
-        %{"type" => "Delete", "object" => object_id, "actor" => _actor, "id" => _id} = data,
+        %{"type" => "Delete", "object" => object_id, "actor" => actor, "id" => _id} = data,
         _options
       ) do
     object_id = Utils.get_ap_id(object_id)
@@ -653,7 +653,30 @@ defmodule Pleroma.Web.ActivityPub.Transmogrifier do
          {:ok, activity} <- ActivityPub.delete(object, false) do
       {:ok, activity}
     else
-      _e -> :error
+      nil ->
+        case User.get_cached_by_ap_id(object_id) do
+          %User{ap_id: ^actor} = user ->
+            {:ok, followers} = User.get_followers(user)
+
+            Enum.each(followers, fn follower ->
+              User.unfollow(follower, user)
+            end)
+
+            {:ok, friends} = User.get_friends(user)
+
+            Enum.each(friends, fn followed ->
+              User.unfollow(user, followed)
+            end)
+
+            User.invalidate_cache(user)
+            Repo.delete(user)
+
+          nil ->
+            :error
+        end
+
+      _e ->
+        :error
     end
   end