From 0604b0dd091682727d26567e6166fb89db842a9c Mon Sep 17 00:00:00 2001
From: Alex Gleason <alex@alexgleason.me>
Date: Tue, 25 Jan 2022 12:33:26 -0600
Subject: ForceMentionsInContent: don't mention self

---
 .../activity_pub/mrf/force_mentions_in_content.ex  | 14 +++++++++++++
 .../mrf/force_mentions_in_content_test.exs         | 24 ++++++++++++++++++++++
 2 files changed, 38 insertions(+)

diff --git a/lib/pleroma/web/activity_pub/mrf/force_mentions_in_content.ex b/lib/pleroma/web/activity_pub/mrf/force_mentions_in_content.ex
index c9b022cf8..71c240727 100644
--- a/lib/pleroma/web/activity_pub/mrf/force_mentions_in_content.ex
+++ b/lib/pleroma/web/activity_pub/mrf/force_mentions_in_content.ex
@@ -3,6 +3,8 @@
 # SPDX-License-Identifier: AGPL-3.0-only
 
 defmodule Pleroma.Web.ActivityPub.MRF.ForceMentionsInContent do
+  require Pleroma.Constants
+
   alias Pleroma.Formatter
   alias Pleroma.Object
   alias Pleroma.User
@@ -58,6 +60,17 @@ defp sort_replied_user(users, %User{id: user_id} = user) do
 
   defp sort_replied_user(users, _), do: users
 
+  # Drop constants and the actor's own AP ID
+  defp clean_recipients(recipients, object) do
+    Enum.reject(recipients, fn ap_id ->
+      ap_id in [
+        object["object"]["actor"],
+        Pleroma.Constants.as_public(),
+        Pleroma.Web.ActivityPub.Utils.as_local_public()
+      ]
+    end)
+  end
+
   @impl true
   def filter(%{"type" => "Create", "object" => %{"type" => "Note", "to" => to}} = object)
       when is_list(to) do
@@ -69,6 +82,7 @@ def filter(%{"type" => "Create", "object" => %{"type" => "Note", "to" => to}} =
 
     mention_users =
       to
+      |> clean_recipients(object)
       |> Enum.map(&User.get_cached_by_ap_id/1)
       |> Enum.reject(&is_nil/1)
       |> sort_replied_user(replied_to_user)
diff --git a/test/pleroma/web/activity_pub/mrf/force_mentions_in_content_test.exs b/test/pleroma/web/activity_pub/mrf/force_mentions_in_content_test.exs
index 3bc07be94..589e8fdfb 100644
--- a/test/pleroma/web/activity_pub/mrf/force_mentions_in_content_test.exs
+++ b/test/pleroma/web/activity_pub/mrf/force_mentions_in_content_test.exs
@@ -85,4 +85,28 @@ test "the replied-to user is sorted to the left" do
     assert filtered ==
              "<span class=\"recipients-inline\"><span class=\"h-card\"><a class=\"u-url mention\" data-user=\"#{luigi.id}\" href=\"#{luigi.ap_id}\" rel=\"ugc\">@<span>luigi</span></a></span> <span class=\"h-card\"><a class=\"u-url mention\" data-user=\"#{mario.id}\" href=\"#{mario.ap_id}\" rel=\"ugc\">@<span>mario</span></a></span> </span>WHA-HA!"
   end
+
+  test "don't mention self" do
+    mario = insert(:user, nickname: "mario")
+
+    {:ok, post} = CommonAPI.post(mario, %{status: "Mama mia"})
+
+    activity = %{
+      "type" => "Create",
+      "actor" => mario.ap_id,
+      "object" => %{
+        "type" => "Note",
+        "actor" => mario.ap_id,
+        "content" => "I'ma tired...",
+        "to" => [
+          mario.ap_id,
+          Constants.as_public()
+        ],
+        "inReplyTo" => Object.normalize(post).data["id"]
+      }
+    }
+
+    {:ok, %{"object" => %{"content" => filtered}}} = ForceMentionsInContent.filter(activity)
+    assert filtered == "I'ma tired..."
+  end
 end
-- 
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