transmogrifier: use User.delete() instead of handrolled user deletion code for remote users

Closes #1104

CHANGELOG.md

@@ -12,6 +12,7 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/).
 - Migrations: fix a sporadic migration failure
 - Metadata rendering errors resulting in the entire page being inaccessible
 - Federation/MediaProxy not working with instances that have wrong certificate order
+- ActivityPub S2S: remote user deletions now work the same as local user deletions.
 
 ### Changed
 - Configuration: OpenGraph and TwitterCard providers enabled by default

lib/pleroma/web/activity_pub/transmogrifier.ex

@@ -614,7 +614,7 @@ def handle_incoming(
   # 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
       ) do
     object_id = Utils.get_ap_id(object_id)
 
@@ -625,7 +625,17 @@ def handle_incoming(
          {: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 ->
+            User.delete(user)
+
+          nil ->
+            :error
+        end
+
+      _e ->
+        :error
     end
   end
 

test/notification_test.exs

@@ -531,5 +531,63 @@ test "replying to a deleted post without tagging does not generate a notificatio
 
       assert Enum.empty?(Notification.for_user(user))
     end
+
+    test "notifications are deleted if a local user is deleted" do
+      user = insert(:user)
+      other_user = insert(:user)
+
+      {:ok, _activity} =
+        CommonAPI.post(user, %{"status" => "hi @#{other_user.nickname}", "visibility" => "direct"})
+
+      refute Enum.empty?(Notification.for_user(other_user))
+
+      User.delete(user)
+
+      assert Enum.empty?(Notification.for_user(other_user))
+    end
+
+    test "notifications are deleted if a remote user is deleted" do
+      remote_user = insert(:user)
+      local_user = insert(:user)
+
+      dm_message = %{
+        "@context" => "https://www.w3.org/ns/activitystreams",
+        "type" => "Create",
+        "actor" => remote_user.ap_id,
+        "id" => remote_user.ap_id <> "/activities/test",
+        "to" => [local_user.ap_id],
+        "cc" => [],
+        "object" => %{
+          "type" => "Note",
+          "content" => "Hello!",
+          "tag" => [
+            %{
+              "type" => "Mention",
+              "href" => local_user.ap_id,
+              "name" => "@#{local_user.nickname}"
+            }
+          ],
+          "to" => [local_user.ap_id],
+          "cc" => [],
+          "attributedTo" => remote_user.ap_id
+        }
+      }
+
+      {:ok, _dm_activity} = Transmogrifier.handle_incoming(dm_message)
+
+      refute Enum.empty?(Notification.for_user(local_user))
+
+      delete_user_message = %{
+        "@context" => "https://www.w3.org/ns/activitystreams",
+        "id" => remote_user.ap_id <> "/activities/delete",
+        "actor" => remote_user.ap_id,
+        "type" => "Delete",
+        "object" => remote_user.ap_id
+      }
+
+      {:ok, _delete_activity} = Transmogrifier.handle_incoming(delete_user_message)
+
+      assert Enum.empty?(Notification.for_user(local_user))
+    end
   end
 end