SideEffects: On deletion, reduce the reply count cache

lib/pleroma/web/activity_pub/side_effects.ex

@@ -35,6 +35,7 @@ def handle(%{data: %{"type" => "Like"}} = object, meta) do
   # - Replace object with Tombstone
   # - Set up notification
   # - Reduce the user note count
+  # - TODO: Reduce the reply count
   def handle(%{data: %{"type" => "Delete", "object" => deleted_object}} = object, meta) do
     deleted_object =
       Object.normalize(deleted_object, false) || User.get_cached_by_ap_id(deleted_object)
@@ -47,6 +48,11 @@ def handle(%{data: %{"type" => "Delete", "object" => deleted_object}} = object,
             User.remove_pinnned_activity(user, activity)
 
             {:ok, user} = ActivityPub.decrease_note_count_if_public(user, deleted_object)
+
+            if in_reply_to = deleted_object.data["inReplyTo"] do
+              Object.decrease_replies_count(in_reply_to)
+            end
+
             ActivityPub.stream_out(object)
             ActivityPub.stream_out_participations(deleted_object, user)
             :ok

test/web/activity_pub/side_effects_test.exs

@@ -23,19 +23,25 @@ defmodule Pleroma.Web.ActivityPub.SideEffectsTest do
   describe "delete objects" do
     setup do
       user = insert(:user)
-      {:ok, post} = CommonAPI.post(user, %{"status" => "hey"})
+      other_user = insert(:user)
+
+      {:ok, op} = CommonAPI.post(other_user, %{"status" => "big oof"})
+      {:ok, post} = CommonAPI.post(user, %{"status" => "hey", "in_reply_to_id" => op})
       object = Object.normalize(post)
       {:ok, delete_data, _meta} = Builder.delete(user, object.data["id"])
       {:ok, delete_user_data, _meta} = Builder.delete(user, user.ap_id)
       {:ok, delete, _meta} = ActivityPub.persist(delete_data, local: true)
       {:ok, delete_user, _meta} = ActivityPub.persist(delete_user_data, local: true)
-      %{user: user, delete: delete, post: post, object: object, delete_user: delete_user}
+      %{user: user, delete: delete, post: post, object: object, delete_user: delete_user, op: op}
     end
 
-    test "it handles object deletions", %{delete: delete, post: post, object: object, user: user} do
+    test "it handles object deletions", %{
-      # In object deletions, the object is replaced by a tombstone and the
+      delete: delete,
-      # create activity is deleted.
+      post: post,
-
+      object: object,
+      user: user,
+      op: op
+    } do
       with_mock Pleroma.Web.ActivityPub.ActivityPub, [:passthrough],
         stream_out: fn _ -> nil end,
         stream_out_participations: fn _, _ -> nil end do
@@ -52,6 +58,10 @@ test "it handles object deletions", %{delete: delete, post: post, object: object
 
       user = User.get_by_id(user.id)
       assert user.note_count == 0
+
+      object = Object.normalize(op.data["object"], false)
+
+      assert object.data["repliesCount"] == 0
     end
 
     test "it handles user deletions", %{delete_user: delete, user: user} do