AP ingest: fill missing attributedTo from activity

lib/pleroma/object/containment.ex

@@ -15,12 +15,28 @@ defmodule Pleroma.Object.Containment do
     actor
   end
 
+  def get_actor(%{"actor" => nil, "attributedTo" => actor}) when not is_nil(actor) do
+    get_actor(%{"actor" => actor})
+  end
+
+  def get_actor(%{"actor" => nil}), do: nil
+
+  def get_actor(%{"actor" => []}), do: nil
+
   def get_actor(%{"actor" => actor}) when is_list(actor) do
-    if is_binary(Enum.at(actor, 0)) do
-      Enum.at(actor, 0)
-    else
-      Enum.find(actor, fn %{"type" => type} -> type in ["Person", "Service", "Application"] end)
-      |> Map.get("id")
+    case actor do
+      [first | _] when is_binary(first) ->
+        first
+
+      _ ->
+        Enum.find_value(actor, fn
+          %{"type" => type, "id" => id}
+          when type in ["Person", "Service", "Application"] and is_binary(id) ->
+            id
+
+          _ ->
+            nil
+        end)
     end
   end
 
@@ -28,10 +44,6 @@ defmodule Pleroma.Object.Containment do
     id
   end
 
-  def get_actor(%{"actor" => nil, "attributedTo" => actor}) when not is_nil(actor) do
-    get_actor(%{"actor" => actor})
-  end
-
   def get_object(%{"object" => id}) when is_binary(id) do
     id
   end

lib/pleroma/web/activity_pub/object_validator.ex

@@ -118,6 +118,7 @@ defmodule Pleroma.Web.ActivityPub.ObjectValidator do
       when objtype in ~w[Question Answer Audio Video Image Event Article Note Page] do
     with {:ok, object_data} <-
            object
+           |> CommonFixes.maybe_set_attributed_to_from_activity(create_activity)
            |> CommonFixes.maybe_add_language_from_activity(create_activity)
            |> cast_and_apply_and_stringify_with_history(),
          meta = Keyword.put(meta, :object_data, object_data),
@@ -172,6 +173,7 @@ defmodule Pleroma.Web.ActivityPub.ObjectValidator do
          {_, {:ok, object_data, _}} <-
            {:object_validation,
             object
+            |> CommonFixes.maybe_set_attributed_to_from_activity(update_activity)
             |> CommonFixes.maybe_add_language_from_activity(update_activity)
             |> validate(meta)},
          meta = Keyword.put(meta, :object_data, object_data),

lib/pleroma/web/activity_pub/object_validators/common_fixes.ex

@@ -91,6 +91,17 @@ defmodule Pleroma.Web.ActivityPub.ObjectValidators.CommonFixes do
     |> Map.put("attributedTo", actor)
   end
 
+  def maybe_set_attributed_to_from_activity(object, activity) when is_map(object) do
+    if is_nil(object["attributedTo"]) and is_nil(object["actor"]) do
+      case Containment.get_actor(activity) do
+        actor when is_binary(actor) -> Map.put(object, "attributedTo", actor)
+        _ -> object
+      end
+    else
+      object
+    end
+  end
+
   def fix_activity_context(data, %Object{data: %{"context" => object_context}}) do
     data
     |> Map.put("context", object_context)

test/fixtures/fedidev.fun/missing_attributed_to.json

@@ -0,0 +1,25 @@
+{
+  "@context": [
+    "https://www.w3.org/ns/activitystreams"
+  ],
+  "type": "Create",
+  "id": "https://fedidev.fun/activity/missing-attributedto",
+  "actor": "https://fedidev.fun/users/alice",
+  "to": [
+    "https://www.w3.org/ns/activitystreams#Public"
+  ],
+  "cc": [],
+  "published": "2025-11-21T14:42:00Z",
+  "object": {
+    "type": "Note",
+    "id": "https://fedidev.fun/objects/note-missing-attributedto",
+    "attributedTo": null,
+    "to": [
+      "https://www.w3.org/ns/activitystreams#Public"
+    ],
+    "cc": [],
+    "published": "2025-11-21T14:42:00Z",
+    "content": "object without attributedTo"
+  }
+}
+

test/pleroma/web/activity_pub/transmogrifier/fedidev_fun_missing_attributed_to_test.exs

@@ -0,0 +1,49 @@
+# Pleroma: A lightweight social networking server
+# Copyright © 2017-2022 Pleroma Authors <https://pleroma.social/>
+# SPDX-License-Identifier: AGPL-3.0-only
+
+defmodule Pleroma.Web.ActivityPub.Transmogrifier.FedidevFunMissingAttributedToTest do
+  use Oban.Testing, repo: Pleroma.Repo
+  use Pleroma.DataCase
+
+  alias Pleroma.Object
+  alias Pleroma.User
+  alias Pleroma.Web.ActivityPub.Transmogrifier
+
+  import Pleroma.Factory
+
+  setup_all do
+    Tesla.Mock.mock_global(fn env -> apply(HttpRequestMock, :request, [env]) end)
+    :ok
+  end
+
+  defp ensure_remote_actor!(ap_id) when is_binary(ap_id) do
+    case User.get_cached_by_ap_id(ap_id) do
+      %User{} ->
+        :ok
+
+      _ ->
+        insert(:user,
+          local: false,
+          ap_id: ap_id,
+          follower_address: ap_id <> "/followers",
+          following_address: ap_id <> "/following",
+          featured_address: ap_id <> "/collections/featured",
+          inbox: ap_id <> "/inbox"
+        )
+
+        :ok
+    end
+  end
+
+  test "inherits attributedTo from surrounding activity" do
+    data = File.read!("test/fixtures/fedidev.fun/missing_attributed_to.json") |> Jason.decode!()
+    ensure_remote_actor!(data["actor"])
+
+    assert {:ok, activity} = Transmogrifier.handle_incoming(data)
+    object = Object.normalize(activity.data["object"], fetch: false)
+
+    assert object.data["attributedTo"] == data["actor"]
+    assert object.data["actor"] == data["actor"]
+  end
+end