From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
From: Jason Penilla <11360596+jpenilla@users.noreply.github.com>
Date: Sat, 31 Oct 2020 11:49:01 -0700
Subject: [PATCH] Fix client lag on advancement loading

When new advancements are added via the UnsafeValues#loadAdvancement
API, it triggers a full datapack reload when this is not necessary. The
advancement is already loaded directly into the advancement registry,
and the point of saving the advancement to the Bukkit datapack seems to
be for persistence. By removing the call to reload datapacks when an
advancement is loaded, the client no longer completely freezes up when
adding a new advancement.
To ensure the client still receives the updated advancement data, we
manually reload the advancement data for all players, which
normally takes place as a part of the datapack reloading.

diff --git a/src/main/java/org/bukkit/craftbukkit/util/CraftMagicNumbers.java b/src/main/java/org/bukkit/craftbukkit/util/CraftMagicNumbers.java
index 93505eba28d9fb20ce25866e932fc1cdcb006db8..af8fde74b3162d2de740ecae1122b4f2115baeb6 100644
--- a/src/main/java/org/bukkit/craftbukkit/util/CraftMagicNumbers.java
+++ b/src/main/java/org/bukkit/craftbukkit/util/CraftMagicNumbers.java
@@ -317,7 +317,13 @@ public final class CraftMagicNumbers implements UnsafeValues {
                     Bukkit.getLogger().log(Level.SEVERE, "Error saving advancement " + key, ex);
                 }
 
-                MinecraftServer.getServer().getPlayerList().reloadResources();
+                // Paper start - Fix client lag on advancement loading
+                //MinecraftServer.getServer().getPlayerList().reload();
+                MinecraftServer.getServer().getPlayerList().getPlayers().forEach(player -> {
+                    player.getAdvancements().reload(MinecraftServer.getServer().getAdvancements());
+                    player.getAdvancements().flushDirty(player);
+                });
+                // Paper end - Fix client lag on advancement loading
 
                 return bukkit;
             }