Merge pull request 'Federation: refetch a stale Move target once' (#8051) from lambadalambda/pleroma:fix/move-refetch-target into develop

Reviewed-on: https://git.pleroma.social/pleroma/pleroma/pulls/8051

changelog.d/move-refetch-target.fix

@@ -0,0 +1 @@
+Accept a Move when the cached remote target does not list the alias yet, by refetching the target once

lib/pleroma/web/activity_pub/transmogrifier.ex

@@ -799,7 +799,7 @@ defmodule Pleroma.Web.ActivityPub.Transmogrifier do
        ) do
     with %User{} = origin_user <- User.get_cached_by_ap_id(origin_actor),
          {:ok, %User{} = target_user} <- User.get_or_fetch_by_ap_id(target_actor),
-         true <- origin_actor in target_user.also_known_as do
+         {:ok, %User{} = target_user} <- refetch_unless_aliased(target_user, origin_actor) do
       ActivityPub.move(origin_user, target_user, false)
     else
       _e -> :error
@@ -1204,4 +1204,20 @@ defmodule Pleroma.Web.ActivityPub.Transmogrifier do
   def maybe_fix_user_url(data), do: data
 
   def maybe_fix_user_object(data), do: maybe_fix_user_url(data)
+
+  # A Move usually follows right after the alias was added, which the cached
+  # remote target may not have yet.
+  defp refetch_unless_aliased(%User{} = target, origin_ap_id, refetch? \\ true) do
+    cond do
+      origin_ap_id in target.also_known_as ->
+        {:ok, target}
+
+      refetch? and not target.local ->
+        with {:ok, %User{} = target} <- User.fetch_by_ap_id(target.ap_id),
+             do: refetch_unless_aliased(target, origin_ap_id, false)
+
+      true ->
+        :error
+    end
+  end
 end

test/pleroma/web/activity_pub/transmogrifier_test.exs

@@ -147,6 +147,53 @@ defmodule Pleroma.Web.ActivityPub.TransmogrifierTest do
       assert activity.data["type"] == "Move"
     end
 
+    test "it refetches a cached remote Move target that lacks the alias" do
+      old_user = insert(:user, local: false, ap_id: "https://old.example/users/old")
+
+      new_user =
+        insert(:user,
+          local: false,
+          ap_id: "https://new.example/users/new",
+          nickname: "new@new.example",
+          last_refreshed_at: NaiveDateTime.utc_now()
+        )
+
+      actor = %{
+        "@context" => "https://www.w3.org/ns/activitystreams",
+        "id" => new_user.ap_id,
+        "type" => "Person",
+        "preferredUsername" => "new",
+        "inbox" => new_user.ap_id <> "/inbox",
+        "outbox" => new_user.ap_id <> "/outbox",
+        "followers" => new_user.ap_id <> "/followers",
+        "following" => new_user.ap_id <> "/following",
+        "alsoKnownAs" => [old_user.ap_id]
+      }
+
+      Tesla.Mock.mock(fn
+        %{method: :get, url: "https://new.example/users/new"} ->
+          %Tesla.Env{
+            status: 200,
+            headers: [{"content-type", "application/activity+json"}],
+            body: Jason.encode!(actor)
+          }
+
+        _ ->
+          %Tesla.Env{status: 404}
+      end)
+
+      message = %{
+        "@context" => "https://www.w3.org/ns/activitystreams",
+        "type" => "Move",
+        "actor" => old_user.ap_id,
+        "object" => old_user.ap_id,
+        "target" => new_user.ap_id
+      }
+
+      assert {:ok, %Activity{data: %{"type" => "Move"}}} = Transmogrifier.handle_incoming(message)
+      assert old_user.ap_id in User.get_cached_by_ap_id(new_user.ap_id).also_known_as
+    end
+
     test "it fixes both the Create and object contexts in a reply" do
       insert(:user, ap_id: "https://mk.absturztau.be/users/8ozbzjs3o8")
       insert(:user, ap_id: "https://p.helene.moe/users/helene")