Transmogrifier: filtering weirdness in address fields

lib/pleroma/web/activity_pub/transmogrifier.ex

@@ -62,15 +62,17 @@ def fix_summary(%{"summary" => _} = object) do
   def fix_summary(object), do: Map.put(object, "summary", "")
 
   def fix_addressing_list(map, field) do
-    cond do
-      is_binary(map[field]) ->
-        Map.put(map, field, [map[field]])
+    addrs = map[field]
 
-      is_nil(map[field]) ->
-        Map.put(map, field, [])
+    cond do
+      is_list(addrs) ->
+        Map.put(map, field, Enum.filter(addrs, &is_binary/1))
+
+      is_binary(addrs) ->
+        Map.put(map, field, [addrs])
 
       true ->
-        map
+        Map.put(map, field, [])
     end
   end
 

test/web/activity_pub/transmogrifier_test.exs

@@ -774,6 +774,29 @@ test "it correctly processes messages with non-array cc field" do
       assert [user.follower_address] == activity.data["to"]
     end
 
+    test "it correctly processes messages with weirdness in address fields" do
+      user = insert(:user)
+
+      message = %{
+        "@context" => "https://www.w3.org/ns/activitystreams",
+        "to" => [nil, user.follower_address],
+        "cc" => ["https://www.w3.org/ns/activitystreams#Public", ["¿"]],
+        "type" => "Create",
+        "object" => %{
+          "content" => "…",
+          "type" => "Note",
+          "attributedTo" => user.ap_id,
+          "inReplyTo" => nil
+        },
+        "actor" => user.ap_id
+      }
+
+      assert {:ok, activity} = Transmogrifier.handle_incoming(message)
+
+      assert ["https://www.w3.org/ns/activitystreams#Public"] == activity.data["cc"]
+      assert [user.follower_address] == activity.data["to"]
+    end
+
     test "it accepts Move activities" do
       old_user = insert(:user)
       new_user = insert(:user)