Deletion: Handle the case of pruned objects.

lib/pleroma/user.ex

@@ -1554,10 +1554,23 @@ defmodule Pleroma.User do
     |> Stream.run()
   end
 
-  defp delete_activity(%{data: %{"type" => "Create", "object" => object}}, user) do
-    {:ok, delete_data, _} = Builder.delete(user, object)
+  defp delete_activity(%{data: %{"type" => "Create", "object" => object}} = activity, user) do
+    with {_, %Object{}} <- {:find_object, Object.get_by_ap_id(object)},
+         {:ok, delete_data, _} <- Builder.delete(user, object) do
+      Pipeline.common_pipeline(delete_data, local: user.local)
+    else
+      {:find_object, nil} ->
+        # We have the create activity, but not the object, it was probably pruned.
+        # Insert a tombstone and try again
+        with {:ok, tombstone_data, _} <- Builder.tombstone(user.ap_id, object),
+             {:ok, _tombstone} <- Object.create(tombstone_data) do
+          delete_activity(activity, user)
+        end
 
-    Pipeline.common_pipeline(delete_data, local: user.local)
+      e ->
+        Logger.error("Could not delete #{object} created by #{activity.data["ap_id"]}")
+        Logger.error("Error: #{inspect(e)}")
+    end
   end
 
   defp delete_activity(%{data: %{"type" => type}} = activity, user)

lib/pleroma/web/activity_pub/builder.ex

@@ -62,6 +62,16 @@ defmodule Pleroma.Web.ActivityPub.Builder do
      }, []}
   end
 
+  @spec tombstone(String.t(), String.t()) :: {:ok, map(), keyword()}
+  def tombstone(actor, id) do
+    {:ok,
+     %{
+       "id" => id,
+       "actor" => actor,
+       "type" => "Tombstone"
+     }, []}
+  end
+
   @spec like(User.t(), Object.t()) :: {:ok, map(), keyword()}
   def like(actor, object) do
     with {:ok, data, meta} <- object_action(actor, object) do

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

@@ -51,6 +51,7 @@ defmodule Pleroma.Web.ActivityPub.ObjectValidators.DeleteValidator do
     Page
     Question
     Video
+    Tombstone
   }
   def validate_data(cng) do
     cng

lib/pleroma/web/activity_pub/transmogrifier.ex

@@ -14,7 +14,9 @@ defmodule Pleroma.Web.ActivityPub.Transmogrifier do
   alias Pleroma.Repo
   alias Pleroma.User
   alias Pleroma.Web.ActivityPub.ActivityPub
+  alias Pleroma.Web.ActivityPub.Builder
   alias Pleroma.Web.ActivityPub.ObjectValidator
+  alias Pleroma.Web.ActivityPub.ObjectValidators.Types
   alias Pleroma.Web.ActivityPub.Pipeline
   alias Pleroma.Web.ActivityPub.Utils
   alias Pleroma.Web.ActivityPub.Visibility
@@ -720,6 +722,19 @@ defmodule Pleroma.Web.ActivityPub.Transmogrifier do
       ) do
     with {:ok, activity, _} <- Pipeline.common_pipeline(data, local: false) do
       {:ok, activity}
+    else
+      {:error, {:validate_object, _}} = e ->
+        # Check if we have a create activity for this
+        with {:ok, object_id} <- Types.ObjectID.cast(data["object"]),
+             %Activity{data: %{"actor" => actor}} <-
+               Activity.create_by_object_ap_id(object_id) |> Repo.one(),
+             # We have one, insert a tombstone and retry
+             {:ok, tombstone_data, _} <- Builder.tombstone(actor, object_id),
+             {:ok, _tombstone} <- Object.create(tombstone_data) do
+          handle_incoming(data)
+        else
+          _ -> e
+        end
     end
   end
 

lib/pleroma/web/common_api/common_api.ex

@@ -83,16 +83,35 @@ defmodule Pleroma.Web.CommonAPI do
   end
 
   def delete(activity_id, user) do
-    with {_, %Activity{data: %{"object" => _}} = activity} <-
-           {:find_activity, Activity.get_by_id_with_object(activity_id)},
-         %Object{} = object <- Object.normalize(activity),
+    with {_, %Activity{data: %{"object" => _, "type" => "Create"}} = activity} <-
+           {:find_activity, Activity.get_by_id(activity_id)},
+         {_, %Object{} = object, _} <-
+           {:find_object, Object.normalize(activity, false), activity},
          true <- User.superuser?(user) || user.ap_id == object.data["actor"],
          {:ok, delete_data, _} <- Builder.delete(user, object.data["id"]),
          {:ok, delete, _} <- Pipeline.common_pipeline(delete_data, local: true) do
       {:ok, delete}
     else
-      {:find_activity, _} -> {:error, :not_found}
-      _ -> {:error, dgettext("errors", "Could not delete")}
+      {:find_activity, _} ->
+        {:error, :not_found}
+
+      {:find_object, nil, %Activity{data: %{"actor" => actor, "object" => object}}} ->
+        # We have the create activity, but not the object, it was probably pruned.
+        # Insert a tombstone and try again
+        with {:ok, tombstone_data, _} <- Builder.tombstone(actor, object),
+             {:ok, _tombstone} <- Object.create(tombstone_data) do
+          delete(activity_id, user)
+        else
+          _ ->
+            Logger.error(
+              "Could not insert tombstone for missing object on deletion. Object is #{object}."
+            )
+
+            {:error, dgettext("errors", "Could not delete")}
+        end
+
+      _ ->
+        {:error, dgettext("errors", "Could not delete")}
     end
   end