Use correct logic to determine "attentions" list

lib/pleroma/web/common_api/utils.ex

@@ -259,4 +259,46 @@ defmodule Pleroma.Web.CommonAPI.Utils do
       }
     end)
   end
+
+  def maybe_notify_to_recipients(
+        recipients,
+        %Activity{data: %{"to" => to, "type" => _type}} = _activity
+      ) do
+    recipients ++ to
+  end
+
+  def maybe_notify_mentioned_recipients(
+        recipients,
+        %Activity{data: %{"to" => _to, "type" => type} = data} = _activity
+      )
+      when type == "Create" do
+    object = Object.normalize(data["object"])
+
+    object_data =
+      cond do
+        !is_nil(object) ->
+          object.data
+
+        is_map(data["object"]) ->
+          data["object"]
+
+        true ->
+          %{}
+      end
+
+    tagged_mentions = maybe_extract_mentions(object_data)
+
+    recipients ++ tagged_mentions
+  end
+
+  def maybe_notify_mentioned_recipients(recipients, _), do: recipients
+
+  def maybe_extract_mentions(%{"tag" => tag}) do
+    tag
+    |> Enum.filter(fn x -> is_map(x) end)
+    |> Enum.filter(fn x -> x["type"] == "Mention" end)
+    |> Enum.map(fn x -> x["href"] end)
+  end
+
+  def maybe_extract_mentions(_), do: []
 end

lib/pleroma/web/twitter_api/representers/activity_representer.ex

@@ -155,10 +155,12 @@ defmodule Pleroma.Web.TwitterAPI.Representers.ActivityRepresenter do
     repeated = opts[:for] && opts[:for].ap_id in (object["announcements"] || [])
     pinned = activity.id in user.info.pinned_activities
 
-    mentions = get_mentioned_users(opts[:mentioned] || [], user)
+    mentions = opts[:mentioned] || []
 
     attentions =
-      activity.recipients
+      []
+      |> Utils.maybe_notify_to_recipients(activity)
+      |> Utils.maybe_notify_mentioned_recipients(activity)
       |> Enum.map(fn ap_id -> Enum.find(mentions, fn user -> ap_id == user.ap_id end) end)
       |> Enum.filter(& &1)
       |> Enum.map(fn user -> UserView.render("show.json", %{user: user, for: opts[:for]}) end)
@@ -224,10 +226,6 @@ defmodule Pleroma.Web.TwitterAPI.Representers.ActivityRepresenter do
     end
   end
 
-  defp get_mentioned_users(mentioned, user) do
-    mentioned ++ [user]
-  end
-
   defp to_boolean(false) do
     false
   end

lib/pleroma/web/twitter_api/views/activity_view.ex

@@ -246,7 +246,9 @@ defmodule Pleroma.Web.TwitterAPI.ActivityView do
     pinned = activity.id in user.info.pinned_activities
 
     attentions =
-      activity.recipients
+      []
+      |> Utils.maybe_notify_to_recipients(activity)
+      |> Utils.maybe_notify_mentioned_recipients(activity)
       |> Enum.map(fn ap_id -> get_user(ap_id, opts) end)
       |> Enum.filter(& &1)
       |> Enum.map(fn user -> UserView.render("show.json", %{user: user, for: opts[:for]}) end)