From cb12585098e0cc1e2e85d253812e1898e8034b7f Mon Sep 17 00:00:00 2001
From: lain <lain@soykaf.club>
Date: Fri, 24 Apr 2020 14:37:53 +0200
Subject: [PATCH] Announcements: Prevent race condition.

---
 lib/pleroma/web/activity_pub/activity_pub.ex |  1 +
 test/web/common_api/common_api_test.exs      | 27 ++++++++++++++++++++
 2 files changed, 28 insertions(+)

diff --git a/lib/pleroma/web/activity_pub/activity_pub.ex b/lib/pleroma/web/activity_pub/activity_pub.ex
index c67b3335d..4cce4f13c 100644
--- a/lib/pleroma/web/activity_pub/activity_pub.ex
+++ b/lib/pleroma/web/activity_pub/activity_pub.ex
@@ -438,6 +438,7 @@ def announce(
 
   defp do_announce(user, object, activity_id, local, public) do
     with true <- is_announceable?(object, user, public),
+         object <- Object.get_by_id(object.id),
          announce_data <- make_announce_data(user, object, activity_id, public),
          {:ok, activity} <- insert(announce_data, local),
          {:ok, object} <- add_announce_to_object(activity, object),
diff --git a/test/web/common_api/common_api_test.exs b/test/web/common_api/common_api_test.exs
index e87193c83..1758662b0 100644
--- a/test/web/common_api/common_api_test.exs
+++ b/test/web/common_api/common_api_test.exs
@@ -48,6 +48,33 @@ test "favoriting race condition" do
     assert object.data["like_count"] == 20
   end
 
+  test "repeating race condition" do
+    user = insert(:user)
+    users_serial = insert_list(10, :user)
+    users = insert_list(10, :user)
+
+    {:ok, activity} = CommonAPI.post(user, %{"status" => "."})
+
+    users_serial
+    |> Enum.map(fn user ->
+      CommonAPI.repeat(activity.id, user)
+    end)
+
+    object = Object.get_by_ap_id(activity.data["object"])
+    assert object.data["announcement_count"] == 10
+
+    users
+    |> Enum.map(fn user ->
+      Task.async(fn ->
+        CommonAPI.repeat(activity.id, user)
+      end)
+    end)
+    |> Enum.map(&Task.await/1)
+
+    object = Object.get_by_ap_id(activity.data["object"])
+    assert object.data["announcement_count"] == 20
+  end
+
   test "when replying to a conversation / participation, it will set the correct context id even if no explicit reply_to is given" do
     user = insert(:user)
     {:ok, activity} = CommonAPI.post(user, %{"status" => ".", "visibility" => "direct"})