Handle MRF rejections of incoming AP activities

lib/pleroma/web/activity_pub/activity_pub.ex

@@ -274,6 +274,9 @@ def create(%{to: to, actor: actor, context: context, object: object} = params, f
     else
       {:fake, true, activity} ->
         {:ok, activity}
+
+      {:error, message} ->
+        {:error, message}
     end
   end
 

test/web/federator_test.exs

@@ -213,5 +213,21 @@ test "rejects incoming AP docs with incorrect origin" do
 
       :error = Federator.incoming_ap_doc(params)
     end
+
+    test "it does not crash if MRF rejects the post" do
+      policies = Pleroma.Config.get([:instance, :rewrite_policy])
+      mrf_keyword_policy = Pleroma.Config.get(:mrf_keyword)
+      Pleroma.Config.put([:mrf_keyword, :reject], ["lain"])
+      Pleroma.Config.put([:instance, :rewrite_policy], Pleroma.Web.ActivityPub.MRF.KeywordPolicy)
+
+      params =
+        File.read!("test/fixtures/mastodon-post-activity.json")
+        |> Poison.decode!()
+
+      assert Federator.incoming_ap_doc(params) == :error
+
+      Pleroma.Config.put([:instance, :rewrite_policy], policies)
+      Pleroma.Config.put(:mrf_keyword, mrf_keyword_policy)
+    end
   end
 end