Paper/Spigot-Server-Patches/0452-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.

diff --git a/src/main/java/net/minecraft/server/level/EntityPlayer.java b/src/main/java/net/minecraft/server/level/EntityPlayer.java
index 5b9778c0a7a52ddb05ca7a6864e3b8852cec03e4..eaeac60b2d54d8e7d298ea412d888471a7ea9e79 100644
--- a/src/main/java/net/minecraft/server/level/EntityPlayer.java
+++ b/src/main/java/net/minecraft/server/level/EntityPlayer.java
@@ -239,6 +239,7 @@ public class EntityPlayer extends EntityHuman implements ICrafting {
     public double maxHealthCache;
     public boolean joining = true;
     public boolean sentListPacket = false;
+    public boolean supressTrackerForLogin = false; // Paper
     public Integer clientViewDistance;
     // CraftBukkit end
     public PlayerNaturallySpawnCreaturesEvent playerNaturallySpawnedEvent; // Paper
diff --git a/src/main/java/net/minecraft/server/level/PlayerChunkMap.java b/src/main/java/net/minecraft/server/level/PlayerChunkMap.java
index 80c7ff059b78f55ec9c390bd728186a94074e603..94860c06717e8dcf969277562e88687e9a99aaa4 100644
--- a/src/main/java/net/minecraft/server/level/PlayerChunkMap.java
+++ b/src/main/java/net/minecraft/server/level/PlayerChunkMap.java
@@ -1578,7 +1578,7 @@ public class PlayerChunkMap extends IChunkLoader implements PlayerChunk.d {
         });
     }
 
-    protected void addEntity(Entity entity) {
+    public void addEntity(Entity entity) { // Paper - protected -> public
         org.spigotmc.AsyncCatcher.catchOp("entity track"); // Spigot
         // Paper start - ignore and warn about illegal addEntity calls instead of crashing server
         if (!entity.valid || entity.world != this.world || this.trackedEntities.containsKey(entity.getId())) {
@@ -1587,6 +1587,7 @@ public class PlayerChunkMap extends IChunkLoader implements PlayerChunk.d {
                 .printStackTrace();
             return;
         }
+        if (entity instanceof EntityPlayer && ((EntityPlayer) entity).supressTrackerForLogin) return; // Delay adding to tracker until after list packets
         // Paper end
         if (!(entity instanceof EntityComplexPart)) {
             EntityTypes<?> entitytypes = entity.getEntityType();
diff --git a/src/main/java/net/minecraft/server/players/PlayerList.java b/src/main/java/net/minecraft/server/players/PlayerList.java
index b5600711c29b00f2d7863c0493a21f5080127e9c..c9a8e5c04a10c28ce79368a783dfe3c8e3709583 100644
--- a/src/main/java/net/minecraft/server/players/PlayerList.java
+++ b/src/main/java/net/minecraft/server/players/PlayerList.java
@@ -276,6 +276,12 @@ public abstract class PlayerList {
         this.j.put(entityplayer.getUniqueID(), entityplayer);
         // this.sendAll(new PacketPlayOutPlayerInfo(PacketPlayOutPlayerInfo.EnumPlayerInfoAction.ADD_PLAYER, new EntityPlayer[]{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
+        entityplayer.supressTrackerForLogin = true;
+        worldserver1.addPlayerJoin(entityplayer);
+        this.server.getBossBattleCustomData().a(entityplayer); // see commented out section below worldserver.addPlayerJoin(entityplayer);
+        mountSavedVehicle(entityplayer, worldserver1, nbttagcompound);
+        // Paper end
         // CraftBukkit start
         PlayerJoinEvent playerJoinEvent = new org.bukkit.event.player.PlayerJoinEvent(cserver.getPlayer(entityplayer), PaperAdventure.asAdventure(chatmessage)); // Paper - Adventure
         cserver.getPluginManager().callEvent(playerJoinEvent);
@@ -311,6 +317,8 @@ public abstract class PlayerList {
             entityplayer.playerConnection.sendPacket(new PacketPlayOutPlayerInfo(PacketPlayOutPlayerInfo.EnumPlayerInfoAction.ADD_PLAYER, new EntityPlayer[] { entityplayer1}));
         }
         entityplayer.sentListPacket = true;
+        entityplayer.supressTrackerForLogin = false; // Paper
+        ((WorldServer)entityplayer.world).getChunkProvider().playerChunkMap.addEntity(entityplayer); // Paper - track entity now
         // CraftBukkit end
 
         entityplayer.playerConnection.sendPacket(new PacketPlayOutEntityMetadata(entityplayer.getId(), entityplayer.getDataWatcher(), true)); // CraftBukkit - BungeeCord#2321, send complete data to self on spawn
@@ -336,6 +344,11 @@ public abstract class PlayerList {
             playerconnection.sendPacket(new PacketPlayOutEntityEffect(entityplayer.getId(), mobeffect));
         }
 
+        // Paper start - move vehicle into method so it can be called above - short circuit around that code
+        onPlayerJoinFinish(entityplayer, worldserver1, s1);
+    }
+    private void mountSavedVehicle(EntityPlayer entityplayer, WorldServer worldserver1, NBTTagCompound nbttagcompound) {
+        // Paper end
         if (nbttagcompound != null && nbttagcompound.hasKeyOfType("RootVehicle", 10)) {
             NBTTagCompound nbttagcompound1 = nbttagcompound.getCompound("RootVehicle");
             // CraftBukkit start
@@ -384,6 +397,10 @@ public abstract class PlayerList {
             }
         }
 
+        // Paper start
+    }
+    public void onPlayerJoinFinish(EntityPlayer entityplayer, WorldServer worldserver1, String s1) {
+        // Paper end
         entityplayer.syncInventory();
         // Paper start - Add to collideRule team if needed
         final Scoreboard scoreboard = this.getServer().getWorldServer(World.OVERWORLD).getScoreboard();