ActivityPub: Fetch missing activities on reply.

lib/pleroma/web/activity_pub/activity_pub.ex

@@ -3,6 +3,7 @@ defmodule Pleroma.Web.ActivityPub.ActivityPub do
   alias Pleroma.Web.ActivityPub.Transmogrifier
   alias Pleroma.Web.WebFinger
   alias Pleroma.Web.Federator
+  alias Pleroma.Web.OStatus
   import Ecto.Query
   import Pleroma.Web.ActivityPub.Utils
   require Logger
@@ -325,14 +326,18 @@ def fetch_object_from_id(id) do
     else
       with {:ok, %{body: body, status_code: code}} when code in 200..299 <- @httpoison.get(id, [Accept: "application/activity+json"], follow_redirect: true, timeout: 10000, recv_timeout: 20000),
            {:ok, data} <- Poison.decode(body),
-           data <- Transmogrifier.fix_object(data),
            nil <- Object.get_by_ap_id(data["id"]),
-           %User{} = user <- User.get_or_fetch_by_ap_id(data["attributedTo"]),
-           {:ok, activity} = create(%{to: data["to"], actor: user, context: data["context"], object: data, local: false, additional: %{"cc" => data["cc"]}}) do
+           params <- %{"type" => "Create", "to" => data["to"], "cc" => data["cc"], "actor" => data["attributedTo"], "object" => data},
+           {:ok, activity} <- Transmogrifier.handle_incoming(params) do
         {:ok, Object.get_by_ap_id(activity.data["object"]["id"])}
       else
         object = %Object{} -> {:ok, object}
-        e -> e
+      e ->
+        Logger.info("Couldn't get object via AP, trying out OStatus fetching...")
+        case OStatus.fetch_activity_from_url(id) do
+          {:ok, [activity | _]} -> {:ok, Object.get_by_ap_id(activity.data["object"]["id"])}
+          _ -> e
+        end
       end
     end
   end

lib/pleroma/web/activity_pub/transmogrifier.ex

@@ -53,6 +53,10 @@ def handle_incoming(%{"type" => "Create", "object" => %{"type" => "Note"} = obje
             ])
       }
 
+      if object["inReplyTo"] do
+        {:ok, object} = ActivityPub.fetch_object_from_id(object["inReplyTo"])
+      end
+
       ActivityPub.create(params)
     else
       %Activity{} = activity -> {:ok, activity}

test/web/activity_pub/activity_pub_test.exs

@@ -268,7 +268,9 @@ test "fetches the latest Follow activity" do
   describe "fetching an object" do
     test "it fetches an object" do
       {:ok, object} = ActivityPub.fetch_object_from_id("http://mastodon.example.org/@admin/99541947525187367")
-      assert Activity.get_create_activity_by_object_ap_id(object.data["id"])
+      assert activity = Activity.get_create_activity_by_object_ap_id(object.data["id"])
+      assert activity.data["id"]
+
       {:ok, object_again} = ActivityPub.fetch_object_from_id("http://mastodon.example.org/@admin/99541947525187367")
 
       assert [attachment] = object.data["attachment"]
@@ -276,6 +278,16 @@ test "it fetches an object" do
 
       assert object == object_again
     end
+
+    test "it works with objects only available via Ostatus" do
+      {:ok, object} = ActivityPub.fetch_object_from_id("https://shitposter.club/notice/2827873")
+      assert activity = Activity.get_create_activity_by_object_ap_id(object.data["id"])
+      assert activity.data["id"]
+
+      {:ok, object_again} = ActivityPub.fetch_object_from_id("https://shitposter.club/notice/2827873")
+
+      assert object == object_again
+    end
   end
 
   describe "following / unfollowing" do

test/web/activity_pub/transmogrifier_test.exs

@@ -22,6 +22,21 @@ test "it ignores an incoming notice if we already have it" do
       assert activity == returned_activity
     end
 
+    test "it fetches replied-to activities if we don't have them" do
+      data = File.read!("test/fixtures/mastodon-post-activity.json")
+      |> Poison.decode!
+
+      object = data["object"]
+      |> Map.put("inReplyTo", "https://shitposter.club/notice/2827873")
+
+      data = data
+      |> Map.put("object", object)
+
+      {:ok, returned_activity} = Transmogrifier.handle_incoming(data)
+
+      assert Activity.get_create_activity_by_object_ap_id("tag:shitposter.club,2017-05-05:noticeId=2827873:objectType=comment")
+    end
+
     test "it works for incoming notices" do
       data = File.read!("test/fixtures/mastodon-post-activity.json") |> Poison.decode!