Notifications: Simplify recipient calculation for some Activities.

Fixes the 'getting notfications for other people's posts' bug.

lib/pleroma/notification.ex

@@ -339,13 +339,7 @@ def get_notified_from_activity(activity, local_only \\ true)
 
   def get_notified_from_activity(%Activity{data: %{"type" => type}} = activity, local_only)
       when type in ["Create", "Like", "Announce", "Follow", "Move", "EmojiReact"] do
-    potential_receiver_ap_ids =
-      []
-      |> Utils.maybe_notify_to_recipients(activity)
-      |> Utils.maybe_notify_mentioned_recipients(activity)
-      |> Utils.maybe_notify_subscribers(activity)
-      |> Utils.maybe_notify_followers(activity)
-      |> Enum.uniq()
+    potential_receiver_ap_ids = get_potential_receiver_ap_ids(activity)
 
     potential_receivers = User.get_users_from_set(potential_receiver_ap_ids, local_only)
 
@@ -363,6 +357,27 @@ def get_notified_from_activity(%Activity{data: %{"type" => type}} = activity, lo
 
   def get_notified_from_activity(_, _local_only), do: {[], []}
 
+  # For some actitivies, only notifity the author of the object
+  def get_potential_receiver_ap_ids(%{data: %{"type" => type, "object" => object_id}})
+      when type in ~w{Like Announce EmojiReact} do
+    case Object.get_cached_by_ap_id(object_id) do
+      %Object{data: %{"actor" => actor}} ->
+        [actor]
+
+      _ ->
+        []
+    end
+  end
+
+  def get_potential_receiver_ap_ids(activity) do
+    []
+    |> Utils.maybe_notify_to_recipients(activity)
+    |> Utils.maybe_notify_mentioned_recipients(activity)
+    |> Utils.maybe_notify_subscribers(activity)
+    |> Utils.maybe_notify_followers(activity)
+    |> Enum.uniq()
+  end
+
   @doc "Filters out AP IDs domain-blocking and not following the activity's actor"
   def exclude_domain_blocker_ap_ids(ap_ids, activity, preloaded_users \\ [])
 

test/notification_test.exs

@@ -12,6 +12,8 @@ defmodule Pleroma.NotificationTest do
   alias Pleroma.Notification
   alias Pleroma.Tests.ObanHelpers
   alias Pleroma.User
+  alias Pleroma.Web.ActivityPub.ActivityPub
+  alias Pleroma.Web.ActivityPub.Builder
   alias Pleroma.Web.ActivityPub.Transmogrifier
   alias Pleroma.Web.CommonAPI
   alias Pleroma.Web.MastodonAPI.NotificationView
@@ -601,6 +603,28 @@ test "it does not send notification to mentioned users in likes" do
       assert other_user not in enabled_receivers
     end
 
+    test "it only notifies the post's author in likes" do
+      user = insert(:user)
+      other_user = insert(:user)
+      third_user = insert(:user)
+
+      {:ok, activity_one} =
+        CommonAPI.post(user, %{
+          "status" => "hey @#{other_user.nickname}!"
+        })
+
+      {:ok, like_data, _} = Builder.like(third_user, activity_one.object)
+
+      {:ok, like, _} =
+        like_data
+        |> Map.put("to", [other_user.ap_id | like_data["to"]])
+        |> ActivityPub.persist(local: true)
+
+      {enabled_receivers, _disabled_receivers} = Notification.get_notified_from_activity(like)
+
+      assert other_user not in enabled_receivers
+    end
+
     test "it does not send notification to mentioned users in announces" do
       user = insert(:user)
       other_user = insert(:user)