#673: Fix Craftworld#isChunkLoaded

The flag for getChunkAt(int, int, ChunkStatus, boolean)
is actually a flag for whether to bring the underlying
PlayerChunk up to the required ticket level to load the
chunk. So, if the chunk is already at the required level,
but has not yet loaded, the call will actually either
start the load if it has not already been started and
block until completion.

This behaviour is not suitable for just
checking if the chunk is loaded.

nms-patches/ChunkProviderServer.patch

@@ -1,6 +1,23 @@
 --- a/net/minecraft/server/ChunkProviderServer.java
 +++ b/net/minecraft/server/ChunkProviderServer.java
-@@ -95,7 +95,7 @@
+@@ -51,6 +51,16 @@
+         this.clearCache();
+     }
+ 
++    // CraftBukkit start - properly implement isChunkLoaded
++    public boolean isChunkLoaded(int chunkX, int chunkZ) {
++        PlayerChunk chunk = this.playerChunkMap.getUpdatingChunk(ChunkCoordIntPair.pair(chunkX, chunkZ));
++        if (chunk == null) {
++            return false;
++        }
++        return chunk.getFullChunk() != null;
++    }
++    // CraftBukkit end
++
+     @Override
+     public LightEngineThreaded getLightEngine() {
+         return this.lightEngine;
+@@ -95,7 +105,7 @@
              for (int l = 0; l < 4; ++l) {
                  if (k == this.cachePos[l] && chunkstatus == this.cacheStatus[l]) {
                      ichunkaccess = this.cacheChunk[l];
@@ -9,7 +26,7 @@
                          return ichunkaccess;
                      }
                  }
-@@ -141,12 +141,12 @@
+@@ -141,12 +151,12 @@
              if (playerchunk == null) {
                  return null;
              } else {
@@ -24,7 +41,7 @@
  
                      if (ichunkaccess1 != null) {
                          this.a(k, ichunkaccess1, ChunkStatus.FULL);
-@@ -173,7 +173,15 @@
+@@ -173,7 +183,15 @@
          int l = 33 + ChunkStatus.a(chunkstatus);
          PlayerChunk playerchunk = this.getChunk(k);
  
@@ -41,7 +58,7 @@
              this.chunkMapDistance.a(TicketType.UNKNOWN, chunkcoordintpair, l, chunkcoordintpair);
              if (this.a(playerchunk, l)) {
                  GameProfilerFiller gameprofilerfiller = this.world.getMethodProfiler();
-@@ -192,7 +200,7 @@
+@@ -192,7 +210,7 @@
      }
  
      private boolean a(@Nullable PlayerChunk playerchunk, int i) {
@@ -50,7 +67,7 @@
      }
  
      public boolean isLoaded(int i, int j) {
-@@ -294,11 +302,31 @@
+@@ -294,11 +312,31 @@
  
      @Override
      public void close() throws IOException {
@@ -83,7 +100,7 @@
      public void tick(BooleanSupplier booleansupplier) {
          this.world.getMethodProfiler().enter("purge");
          this.chunkMapDistance.purgeTickets();
-@@ -318,13 +346,19 @@
+@@ -318,13 +356,19 @@
          this.lastTickTime = i;
          WorldData worlddata = this.world.getWorldData();
          boolean flag = worlddata.getType() == WorldType.DEBUG_ALL_BLOCK_STATES;
@@ -105,7 +122,7 @@
  
              this.world.getMethodProfiler().enter("naturalSpawnCount");
              int l = this.chunkMapDistance.b();
-@@ -353,8 +387,35 @@
+@@ -353,8 +397,35 @@
                              for (int j1 = 0; j1 < i1; ++j1) {
                                  EnumCreatureType enumcreaturetype = aenumcreaturetype1[j1];
  
@@ -142,7 +159,7 @@
  
                                      if (object2intmap.getInt(enumcreaturetype) <= k1) {
                                          SpawnerCreature.a(enumcreaturetype, this.world, chunk, blockposition);
-@@ -507,12 +568,18 @@
+@@ -507,12 +578,18 @@
  
          @Override
          protected boolean executeNext() {

src/main/java/org/bukkit/craftbukkit/CraftWorld.java

@@ -340,8 +340,7 @@ public class CraftWorld implements World {
 
     @Override
     public boolean isChunkLoaded(int x, int z) {
-        net.minecraft.server.Chunk chunk = world.getChunkProvider().getChunkAt(x, z, false);
-        return chunk != null;
+        return world.getChunkProvider().isChunkLoaded(x, z);
     }
 
     @Override
@@ -381,19 +380,18 @@ public class CraftWorld implements World {
 
     @Override
     public boolean unloadChunkRequest(int x, int z) {
-        net.minecraft.server.IChunkAccess chunk = world.getChunkProvider().getChunkAt(x, z, ChunkStatus.FULL, false);
-        if (chunk != null) {
-            world.getChunkProvider().removeTicket(TicketType.PLUGIN, chunk.getPos(), 1, Unit.INSTANCE);
+        if (isChunkLoaded(x, z)) {
+            world.getChunkProvider().removeTicket(TicketType.PLUGIN, new ChunkCoordIntPair(x, z), 1, Unit.INSTANCE);
         }
 
         return true;
     }
 
     private boolean unloadChunk0(int x, int z, boolean save) {
-        net.minecraft.server.Chunk chunk = (net.minecraft.server.Chunk) world.getChunkProvider().getChunkAt(x, z, ChunkStatus.FULL, false);
-        if (chunk == null) {
+        if (!isChunkLoaded(x, z)) {
             return true;
         }
+        net.minecraft.server.Chunk chunk = world.getChunkAt(x, z);
 
         chunk.mustNotSave = !save;
         unloadChunkRequest(x, z);