Return a 422 when trying to reply to a deleted status

changelog.d/reply-to-deleted.change

@@ -0,0 +1 @@
+A 422 error is returned when attempting to reply to a deleted status

lib/pleroma/web/common_api/activity_draft.ex

@@ -129,8 +129,22 @@ defmodule Pleroma.Web.CommonAPI.ActivityDraft do
 
   defp in_reply_to(%{params: %{in_reply_to_status_id: ""}} = draft), do: draft
 
-  defp in_reply_to(%{params: %{in_reply_to_status_id: id}} = draft) when is_binary(id) do
-    %__MODULE__{draft | in_reply_to: Activity.get_by_id(id)}
+  defp in_reply_to(%{params: %{in_reply_to_status_id: :deleted}} = draft) do
+    add_error(draft, dgettext("errors", "Cannot reply to a deleted status"))
+  end
+
+  defp in_reply_to(%{params: %{in_reply_to_status_id: id} = params} = draft) when is_binary(id) do
+    activity = Activity.get_by_id(id)
+
+    params =
+      if is_nil(activity) do
+        # Deleted activities are returned as nil
+        Map.put(params, :in_reply_to_status_id, :deleted)
+      else
+        Map.put(params, :in_reply_to_status_id, activity)
+      end
+
+    in_reply_to(%{draft | params: params})
   end
 
   defp in_reply_to(%{params: %{in_reply_to_status_id: %Activity{} = in_reply_to}} = draft) do

test/pleroma/web/mastodon_api/controllers/status_controller_test.exs

@@ -235,6 +235,16 @@ defmodule Pleroma.Web.MastodonAPI.StatusControllerTest do
       assert Activity.get_in_reply_to_activity(activity).id == replied_to.id
     end
 
+    test "replying to a deleted status", %{user: user, conn: conn} do
+      {:ok, status} = CommonAPI.post(user, %{status: "cofe"})
+      {:ok, _deleted_status} = CommonAPI.delete(status.id, user)
+
+      conn
+      |> put_req_header("content-type", "application/json")
+      |> post("/api/v1/statuses", %{"status" => "xD", "in_reply_to_id" => status.id})
+      |> json_response_and_validate_schema(422)
+    end
+
     test "replying to a direct message with visibility other than direct", %{
       user: user,
       conn: conn