Fix issues with chunk saving. Fixes BUKKIT-2158, BUKKIT-2018 and BUKKIT-2229

src/main/java/net/minecraft/server/Chunk.java

@@ -70,6 +70,7 @@ public class Chunk {
     }
 
     public org.bukkit.Chunk bukkitChunk;
+    public boolean mustSave;
     // CraftBukkit end
 
     public Chunk(World world, byte[] abyte, int i, int j) {

src/main/java/net/minecraft/server/ChunkProviderServer.java

@@ -37,7 +37,7 @@ public class ChunkProviderServer implements IChunkProvider {
     }
 
     public boolean isChunkLoaded(int i, int j) {
-        return !this.unloadQueue.containsKey(i, j) && this.chunks.containsKey(i, j); // CraftBukkit
+        return this.chunks.containsKey(i, j); // CraftBukkit
     }
 
     public void queueUnload(int i, int j) {
@@ -47,11 +47,25 @@ public class ChunkProviderServer implements IChunkProvider {
             int l = j * 16 + 8 - chunkcoordinates.z;
             short short1 = 128;
 
-            if (k < -short1 || k > short1 || l < -short1 || l > short1 || !(this.world.keepSpawnInMemory)) { // CraftBukkit - added 'this.world.keepSpawnInMemory'
+            // CraftBukkit start
-                this.unloadQueue.add(i, j); // CraftBukkit
+            if (k < -short1 || k > short1 || l < -short1 || l > short1 || !(this.world.keepSpawnInMemory)) { // Added 'this.world.keepSpawnInMemory'
+                this.unloadQueue.add(i, j);
+
+                Chunk c = this.chunks.get(i, j);
+                if (c != null) {
+                    c.mustSave = true;
                 }
+            }
+            // CraftBukkit end
         } else {
-            this.unloadQueue.add(i, j); // CraftBukkit
+            // CraftBukkit start
+            this.unloadQueue.add(i, j);
+
+            Chunk c = this.chunks.get(i, j);
+            if (c != null) {
+                c.mustSave = true;
+            }
+            // CraftBukkit end
         }
     }
 

src/main/java/net/minecraft/server/PlayerManager.java

@@ -69,6 +69,15 @@ public class PlayerManager {
 
         return playerinstance;
     }
+    // CraftBukkit start
+    public final boolean isChunkInUse(int x, int z) {
+        PlayerInstance pi = a(x, z, false);
+        if (pi != null) {
+            return (PlayerInstance.b(pi).size() > 0);
+        }
+        return false;
+    }
+    // CraftBukkit end
 
     public void flagDirty(int i, int j, int k) {
         int l = i >> 4;

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

@@ -161,9 +161,11 @@ public class CraftWorld implements World {
         }
 
         net.minecraft.server.Chunk chunk = world.chunkProviderServer.getOrCreateChunk(x, z);
-
+        if (chunk.mustSave) {   // If chunk had previously been queued to save, must do save to avoid loss of that data
+            save = true;
+        }
+        chunk.removeEntities(); // Always remove entities - even if discarding, need to get them out of world table
         if (save && !(chunk instanceof EmptyChunk)) {
-            chunk.removeEntities();
             world.chunkProviderServer.saveChunk(chunk);
             world.chunkProviderServer.saveChunkNOP(chunk);
         }
@@ -216,22 +218,7 @@ public class CraftWorld implements World {
     }
 
     public boolean isChunkInUse(int x, int z) {
-        Player[] players = server.getOnlinePlayers();
+        return world.getPlayerManager().isChunkInUse(x, z);
-
-        for (Player player : players) {
-            Location loc = player.getLocation();
-            if (loc.getWorld() != world.chunkProviderServer.world.getWorld()) {
-                continue;
-            }
-
-            // If the chunk is within 256 blocks of a player, refuse to accept the unload request
-            // This is larger than the distance of loaded chunks that actually surround a player
-            // The player is the center of a 21x21 chunk grid, so the edge is 10 chunks (160 blocks) away from the player
-            if (Math.abs(loc.getBlockX() - (x << 4)) <= 256 && Math.abs(loc.getBlockZ() - (z << 4)) <= 256) {
-                return true;
-            }
-        }
-        return false;
     }
 
     public boolean loadChunk(int x, int z, boolean generate) {