Paper/patches/server/0375-Fix-Longstanding-Broken-behavior-of-PlayerJoinEvent.patch

From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
From: Aikar <aikar@aikar.co>
Date: Sun, 19 Apr 2020 00:05:46 -0400
Subject: [PATCH] Fix Longstanding Broken behavior of PlayerJoinEvent

For years, plugin developers have had to delay many things they do
inside of the PlayerJoinEvent by 1 tick to make it actually work.

This all boiled down to 1 reason why: The event fired before the
player was fully ready and joined to the world!

Additionally, if that player logged out on a vehicle, the event
fired before the vehicle was even loaded, so that plugins had no
access to the vehicle during this event either.

This change finally fixes this issue, fully preparing the player
into the world as a fully ready entity, vehicle included.

There should be no plugins that break because of this change, but might
improve consistency with other plugins instead.

For example, if 2 plugins listens to this event, and the first one
teleported the player in the event, then the 2nd plugin actually
would be getting a valid player!

This was very non deterministic. This change will ensure every plugin
receives a deterministic result, and should no longer require 1 tick
delays anymore.

== AT ==
public net.minecraft.server.level.ChunkMap addEntity(Lnet/minecraft/world/entity/Entity;)V

diff --git a/src/main/java/net/minecraft/server/level/ChunkMap.java b/src/main/java/net/minecraft/server/level/ChunkMap.java
index fdf4da153f57dea2e83ced0c4b56fdb8bd10aa74..4fa2076efd11a628e17d8124f3d89342a3299375 100644
--- a/src/main/java/net/minecraft/server/level/ChunkMap.java
+++ b/src/main/java/net/minecraft/server/level/ChunkMap.java
@@ -1556,6 +1556,7 @@ public class ChunkMap extends ChunkStorage implements ChunkHolder.PlayerProvider
                 + ": " + entity  + (this.entityMap.containsKey(entity.getId()) ? " ALREADY CONTAINED (This would have crashed your server)" : ""), new Throwable());
             return;
         }
+        if (entity instanceof ServerPlayer && ((ServerPlayer) entity).supressTrackerForLogin) return; // Delay adding to tracker until after list packets
         // Paper end
         if (!(entity instanceof EnderDragonPart)) {
             EntityType<?> entitytypes = entity.getType();
diff --git a/src/main/java/net/minecraft/server/level/ServerPlayer.java b/src/main/java/net/minecraft/server/level/ServerPlayer.java
index 77859358366eb51282bedf61c8b0094302548e2a..fcf875c6145c2428cab7a801442f34adc098b3ce 100644
--- a/src/main/java/net/minecraft/server/level/ServerPlayer.java
+++ b/src/main/java/net/minecraft/server/level/ServerPlayer.java
@@ -265,6 +265,7 @@ public class ServerPlayer extends Player {
     public double maxHealthCache;
     public boolean joining = true;
     public boolean sentListPacket = false;
+    public boolean supressTrackerForLogin = false; // Paper
     public String kickLeaveMessage = null; // SPIGOT-3034: Forward leave message to PlayerQuitEvent
     // CraftBukkit end
     public boolean isRealPlayer; // Paper
diff --git a/src/main/java/net/minecraft/server/players/PlayerList.java b/src/main/java/net/minecraft/server/players/PlayerList.java
index d1e5db7b0b260002198b1262f914d3c5a30cd2d9..fdd518b5ea21ae617069fd03429712de4b44841b 100644
--- a/src/main/java/net/minecraft/server/players/PlayerList.java
+++ b/src/main/java/net/minecraft/server/players/PlayerList.java
@@ -297,6 +297,12 @@ public abstract class PlayerList {
         this.playersByUUID.put(player.getUUID(), player);
         // this.broadcastAll(ClientboundPlayerInfoUpdatePacket.createPlayerInitializing(List.of(entityplayer))); // CraftBukkit - replaced with loop below
 
+        // Paper start - correctly register player BEFORE PlayerJoinEvent, so the entity is valid and doesn't require tick delay hacks
+        player.supressTrackerForLogin = true;
+        worldserver1.addNewPlayer(player);
+        this.server.getCustomBossEvents().onPlayerConnect(player); // see commented out section below worldserver.addPlayerJoin(entityplayer);
+        mountSavedVehicle(player, worldserver1, nbttagcompound);
+        // Paper end
         // CraftBukkit start
         CraftPlayer bukkitPlayer = player.getBukkitEntity();
 
@@ -335,6 +341,8 @@ public abstract class PlayerList {
             player.connection.send(ClientboundPlayerInfoUpdatePacket.createPlayerInitializing(List.of(entityplayer1)));
         }
         player.sentListPacket = true;
+        player.supressTrackerForLogin = false; // Paper
+        ((ServerLevel)player.level()).getChunkSource().chunkMap.addEntity(player); // Paper - track entity now
         // CraftBukkit end
 
         player.getEntityData().refresh(player); // CraftBukkit - BungeeCord#2321, send complete data to self on spawn
@@ -357,6 +365,11 @@ public abstract class PlayerList {
             playerconnection.send(new ClientboundUpdateMobEffectPacket(player.getId(), mobeffect));
         }
 
+        // Paper start - move vehicle into method so it can be called above - short circuit around that code
+        onPlayerJoinFinish(player, worldserver1, s1);
+    }
+    private void mountSavedVehicle(ServerPlayer player, ServerLevel worldserver1, CompoundTag nbttagcompound) {
+        // Paper end
         if (nbttagcompound != null && nbttagcompound.contains("RootVehicle", 10)) {
             CompoundTag nbttagcompound1 = nbttagcompound.getCompound("RootVehicle");
             // CraftBukkit start
@@ -405,6 +418,10 @@ public abstract class PlayerList {
             }
         }
 
+        // Paper start
+    }
+    public void onPlayerJoinFinish(ServerPlayer player, ServerLevel worldserver1, String s1) {
+        // Paper end
         player.initInventoryMenu();
         // CraftBukkit - Moved from above, added world
         // Paper start - Add to collideRule team if needed
@@ -414,6 +431,7 @@ public abstract class PlayerList {
             scoreboard.addPlayerToTeam(player.getScoreboardName(), collideRuleTeam);
         }
         // Paper end
+        // CraftBukkit - Moved from above, added world
         PlayerList.LOGGER.info("{}[{}] logged in with entity id {} at ([{}]{}, {}, {})", player.getName().getString(), s1, player.getId(), worldserver1.serverLevelData.getLevelName(), player.getX(), player.getY(), player.getZ());
     }