Some fixes to AP fetching.

lib/pleroma/web/activity_pub/transmogrifier.ex

@@ -20,8 +20,24 @@ def fix_object(object) do
     |> Map.put("actor", object["attributedTo"])
     |> fix_attachments
     |> fix_context
+    |> fix_in_reply_to
   end
 
+  def fix_in_reply_to(%{"inReplyTo" => in_reply_to_id} = object) when not is_nil(in_reply_to_id) do
+    case ActivityPub.fetch_object_from_id(object["inReplyToAtomUri"] || in_reply_to_id) do
+      {:ok, replied_object} ->
+        activity = Activity.get_create_activity_by_object_ap_id(replied_object.data["id"])
+        object
+        |> Map.put("inReplyTo", replied_object.data["id"])
+        |> Map.put("inReplyToAtomUri", object["inReplyToAtomUri"] || in_reply_to_id)
+        |> Map.put("inReplyToStatusId", activity.id)
+      e ->
+        Logger.error("Couldn't fetch #{object["inReplyTo"]} #{inspect(e)}")
+        object
+    end
+  end
+  def fix_in_reply_to(object), do: object
+
   def fix_context(object) do
     object
     |> Map.put("context", object["conversation"])
@@ -46,19 +62,6 @@ def handle_incoming(%{"type" => "Create", "object" => %{"type" => "Note"} = obje
          %User{} = user <- User.get_or_fetch_by_ap_id(data["actor"]) do
       object = fix_object(data["object"])
 
-      replied_to_id = if object["inReplyTo"] do
-        case ActivityPub.fetch_object_from_id(object["inReplyTo"]) do
-          {:ok, object} -> object.data["id"]
-          e ->
-            Logger.error("Couldn't fetch #{object["inReplyTo"]} #{inspect(e)}")
-            nil
-        end
-      else
-        nil
-      end
-
-      object = Map.put(object, "inReplyTo", replied_to_id || object["inReplyTo"])
-
       params = %{
         to: data["to"],
         object: object,
@@ -139,7 +142,6 @@ def prepare_object(object) do
   def prepare_outgoing(%{"type" => "Create", "object" => %{"type" => "Note"} = object} = data) do
     object = object
     |> prepare_object
-
     data = data
     |> Map.put("object", object)
     |> Map.put("@context", "https://www.w3.org/ns/activitystreams")

test/web/activity_pub/transmogrifier_test.exs

@@ -36,7 +36,27 @@ test "it fetches replied-to activities if we don't have them" do
 
       {: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")
+      assert activity = Activity.get_create_activity_by_object_ap_id("tag:shitposter.club,2017-05-05:noticeId=2827873:objectType=comment")
+      assert returned_activity.data["object"]["inReplyToAtomUri"] == "https://shitposter.club/notice/2827873"
+      assert returned_activity.data["object"]["inReplyToStatusId"] == activity.id
+    end
+
+    test "it works if the activity id isn't an url but an atom-uri is given" do
+      data = File.read!("test/fixtures/mastodon-post-activity.json")
+      |> Poison.decode!
+
+      object = data["object"]
+      |> Map.put("inReplyToAtomUri", "https://shitposter.club/notice/2827873")
+      |> Map.put("inReplyTo", "tag:shitposter.club,2017-05-05:noticeId=2827873:objectType=comment")
+
+      data = data
+      |> Map.put("object", object)
+
+      {:ok, returned_activity} = Transmogrifier.handle_incoming(data)
+
+      assert activity = Activity.get_create_activity_by_object_ap_id("tag:shitposter.club,2017-05-05:noticeId=2827873:objectType=comment")
+      assert returned_activity.data["object"]["inReplyToAtomUri"] == "https://shitposter.club/notice/2827873"
+      assert returned_activity.data["object"]["inReplyToStatusId"] == activity.id
     end
 
     test "it works for incoming notices" do