From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
From: Owen1212055 <23108066+Owen1212055@users.noreply.github.com>
Date: Fri, 29 Jul 2022 12:35:19 -0400
Subject: [PATCH] Warn on plugins accessing faraway chunks


diff --git a/src/main/java/net/minecraft/world/level/Level.java b/src/main/java/net/minecraft/world/level/Level.java
index 38bcf9f410e8a9d47c7d486c28dbc16a6225b650..210c3b6167dac93e550fe849e34b5aa404ab6dce 100644
--- a/src/main/java/net/minecraft/world/level/Level.java
+++ b/src/main/java/net/minecraft/world/level/Level.java
@@ -339,7 +339,7 @@ public abstract class Level implements LevelAccessor, AutoCloseable {
     }
 
     private static boolean isInWorldBoundsHorizontal(BlockPos pos) {
-        return pos.getX() >= -30000000 && pos.getZ() >= -30000000 && pos.getX() < 30000000 && pos.getZ() < 30000000;
+        return pos.getX() >= -30000000 && pos.getZ() >= -30000000 && pos.getX() < 30000000 && pos.getZ() < 30000000; // Diff on change warnUnsafeChunk()
     }
 
     private static boolean isOutsideSpawnableHeight(int y) {
diff --git a/src/main/java/org/bukkit/craftbukkit/CraftWorld.java b/src/main/java/org/bukkit/craftbukkit/CraftWorld.java
index fd732a22916cba613d168bc03a2ef06dd63960a9..1ef380cbd77132b743520f952afa8321042bec6d 100644
--- a/src/main/java/org/bukkit/craftbukkit/CraftWorld.java
+++ b/src/main/java/org/bukkit/craftbukkit/CraftWorld.java
@@ -295,9 +295,24 @@ public class CraftWorld extends CraftRegionAccessor implements World {
     public boolean setSpawnLocation(int x, int y, int z) {
         return this.setSpawnLocation(x, y, z, 0.0F);
     }
+    // Paper start
+    private static void warnUnsafeChunk(String reason, int x, int z) {
+        // if any chunk coord is outside of 30 million blocks
+        if (x > 1875000 || z > 1875000 || x < -1875000 || z < -1875000) {
+            Plugin plugin = io.papermc.paper.util.StackWalkerUtil.getFirstPluginCaller();
+            if (plugin != null) {
+                plugin.getLogger().warning("Plugin is %s at (%s, %s), this might cause issues.".formatted(reason, x, z));
+            }
+            if (net.minecraft.server.MinecraftServer.getServer().isDebugging()) {
+                io.papermc.paper.util.TraceUtil.dumpTraceForThread("Dangerous chunk retrieval");
+            }
+        }
+    }
+    // Paper end
 
     @Override
     public Chunk getChunkAt(int x, int z) {
+        warnUnsafeChunk("getting a faraway chunk", x, z); // Paper
         // Paper start - add ticket to hold chunk for a little while longer if plugin accesses it
         net.minecraft.world.level.chunk.LevelChunk chunk = this.world.getChunkSource().getChunkAtIfLoadedImmediately(x, z);
         if (chunk == null) {
@@ -403,6 +418,7 @@ public class CraftWorld extends CraftRegionAccessor implements World {
         if (!unloadChunk0(x, z, false)) {
             return false;
         }
+        warnUnsafeChunk("regenerating a faraway chunk", x, z); // Paper
 
         final long chunkKey = ChunkCoordIntPair.pair(x, z);
         world.getChunkProvider().unloadQueue.remove(chunkKey);
@@ -476,6 +492,7 @@ public class CraftWorld extends CraftRegionAccessor implements World {
     @Override
     public boolean loadChunk(int x, int z, boolean generate) {
         org.spigotmc.AsyncCatcher.catchOp("chunk load"); // Spigot
+        warnUnsafeChunk("loading a faraway chunk", x, z); // Paper
         ChunkAccess chunk = this.world.getChunkSource().getChunk(x, z, generate || isChunkGenerated(x, z) ? ChunkStatus.FULL : ChunkStatus.EMPTY, true); // Paper
 
         // If generate = false, but the chunk already exists, we will get this back.
@@ -508,6 +525,7 @@ public class CraftWorld extends CraftRegionAccessor implements World {
 
     @Override
     public boolean addPluginChunkTicket(int x, int z, Plugin plugin) {
+        warnUnsafeChunk("adding a faraway chunk ticket", x, z); // Paper
         Preconditions.checkArgument(plugin != null, "null plugin");
         Preconditions.checkArgument(plugin.isEnabled(), "plugin is not enabled");
 
@@ -608,6 +626,7 @@ public class CraftWorld extends CraftRegionAccessor implements World {
 
     @Override
     public void setChunkForceLoaded(int x, int z, boolean forced) {
+        warnUnsafeChunk("forceloading a faraway chunk", x, z); // Paper
         this.getHandle().setChunkForced(x, z, forced);
     }
 
@@ -936,6 +955,7 @@ public class CraftWorld extends CraftRegionAccessor implements World {
 
     @Override
     public int getHighestBlockYAt(int x, int z, org.bukkit.HeightMap heightMap) {
+        warnUnsafeChunk("getting a faraway chunk", x >> 4, z >> 4); // Paper
         // Transient load for this tick
         return this.world.getChunk(x >> 4, z >> 4).getHeight(CraftHeightMap.toNMS(heightMap), x, z);
     }
@@ -2333,6 +2353,7 @@ public class CraftWorld extends CraftRegionAccessor implements World {
     // Spigot end
     // Paper start
     public java.util.concurrent.CompletableFuture<Chunk> getChunkAtAsync(int x, int z, boolean gen, boolean urgent) {
+        warnUnsafeChunk("getting a faraway chunk async", x, z); // Paper
         if (Bukkit.isPrimaryThread()) {
             net.minecraft.world.level.chunk.LevelChunk immediate = this.world.getChunkSource().getChunkAtIfLoadedImmediately(x, z);
             if (immediate != null) {
