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 e8a52daa2ff7782fa39862e97580234058b8766e..6b01d5b5535887eef0ac7b8a5e0a669a2700e83f 100644
--- a/src/main/java/net/minecraft/server/level/ChunkMap.java
+++ b/src/main/java/net/minecraft/server/level/ChunkMap.java
@@ -1036,6 +1036,7 @@ 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 9ec157712b9c891067507f9a308428cee2895fed..ecaf03a72caac6e7866094bae7256f5447a962e4 100644
--- a/src/main/java/net/minecraft/server/level/ServerPlayer.java
+++ b/src/main/java/net/minecraft/server/level/ServerPlayer.java
@@ -259,6 +259,7 @@ public class ServerPlayer extends Player {
     public double maxHealthCache;
     public boolean joining = true;
     public boolean sentListPacket = false;
+    public boolean supressTrackerForLogin = false; // Paper
     public Integer clientViewDistance;
     public String kickLeaveMessage = null; // SPIGOT-3034: Forward leave message to PlayerQuitEvent
     // CraftBukkit end
diff --git a/src/main/java/net/minecraft/server/players/PlayerList.java b/src/main/java/net/minecraft/server/players/PlayerList.java
index 6c5c00e2fb29b5bdd73540badd159778eb1c1ff6..cfc497822e4e1dfc21807ec93bcfabb215cdbb95 100644
--- a/src/main/java/net/minecraft/server/players/PlayerList.java
+++ b/src/main/java/net/minecraft/server/players/PlayerList.java
@@ -291,6 +291,12 @@ 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();
 
@@ -329,6 +335,8 @@ 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
@@ -353,6 +361,11 @@ 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
@@ -401,6 +414,10 @@ 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
@@ -410,6 +427,7 @@ 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());
     }
 
