From e53a9fd15e6749c87193f829f4d33fea1406a21f Mon Sep 17 00:00:00 2001
From: William Pitcock <nenolod@dereferenced.org>
Date: Thu, 7 Mar 2019 12:13:48 +0000
Subject: [PATCH 1/2] MRF: anti followbot: gracefully handle accounts without a
 display name

---
 lib/pleroma/web/activity_pub/mrf/anti_followbot_policy.ex | 12 +++++++++---
 1 file changed, 9 insertions(+), 3 deletions(-)

diff --git a/lib/pleroma/web/activity_pub/mrf/anti_followbot_policy.ex b/lib/pleroma/web/activity_pub/mrf/anti_followbot_policy.ex
index 7c6ad582a..34665a3a6 100644
--- a/lib/pleroma/web/activity_pub/mrf/anti_followbot_policy.ex
+++ b/lib/pleroma/web/activity_pub/mrf/anti_followbot_policy.ex
@@ -23,15 +23,21 @@ defmodule Pleroma.Web.ActivityPub.MRF.AntiFollowbotPolicy do
   defp score_displayname(_), do: 0.0
 
   defp determine_if_followbot(%User{nickname: nickname, name: displayname}) do
+    # nickname will always be a binary string because it's generated by Pleroma.
     nick_score =
       nickname
       |> String.downcase()
       |> score_nickname()
 
+    # displayname will either be a binary string or nil, if a displayname isn't set.
     name_score =
-      displayname
-      |> String.downcase()
-      |> score_displayname()
+      if is_binary(displayname) do
+        displayname
+        |> String.downcase()
+        |> score_displayname()
+      else
+        0.0
+      end
 
     nick_score + name_score
   end

From 3c5926fe913287ee00a0efb93d2a8ecbddfd26c7 Mon Sep 17 00:00:00 2001
From: William Pitcock <nenolod@dereferenced.org>
Date: Thu, 7 Mar 2019 12:20:04 +0000
Subject: [PATCH 2/2] tests: add regression test

---
 test/web/activity_pub/mrf/anti_followbot_policy_test.exs | 15 +++++++++++++++
 1 file changed, 15 insertions(+)

diff --git a/test/web/activity_pub/mrf/anti_followbot_policy_test.exs b/test/web/activity_pub/mrf/anti_followbot_policy_test.exs
index 2ea4f9d3f..37a7bfcf7 100644
--- a/test/web/activity_pub/mrf/anti_followbot_policy_test.exs
+++ b/test/web/activity_pub/mrf/anti_followbot_policy_test.exs
@@ -54,4 +54,19 @@ defmodule Pleroma.Web.ActivityPub.MRF.AntiFollowbotPolicyTest do
 
     {:ok, _} = AntiFollowbotPolicy.filter(message)
   end
+
+  test "it gracefully handles nil display names" do
+    actor = insert(:user, %{name: nil})
+    target = insert(:user)
+
+    message = %{
+      "@context" => "https://www.w3.org/ns/activitystreams",
+      "type" => "Follow",
+      "actor" => actor.ap_id,
+      "object" => target.ap_id,
+      "id" => "https://example.com/activities/1234"
+    }
+
+    {:ok, _} = AntiFollowbotPolicy.filter(message)
+  end
 end