Paper/nms-patches/PlayerChunk.patch

--- a/net/minecraft/server/PlayerChunk.java
+++ b/net/minecraft/server/PlayerChunk.java
@@ -42,7 +42,7 @@
         this.fullChunkFuture = PlayerChunk.UNLOADED_CHUNK_FUTURE;
         this.tickingFuture = PlayerChunk.UNLOADED_CHUNK_FUTURE;
         this.entityTickingFuture = PlayerChunk.UNLOADED_CHUNK_FUTURE;
-        this.chunkSave = CompletableFuture.completedFuture((Object) null);
+        this.chunkSave = CompletableFuture.completedFuture(null); // CraftBukkit - decompile error
         this.dirtyBlocks = new short[64];
         this.location = chunkcoordintpair;
         this.lightEngine = lightengine;
@@ -54,6 +54,15 @@
         this.a(i);
     }
 
+    // CraftBukkit start
+    public Chunk getFullChunk() {
+        if (!getChunkState(this.oldTicketLevel).isAtLeast(PlayerChunk.State.BORDER)) return null; // note: using oldTicketLevel for isLoaded checks
+        CompletableFuture<Either<IChunkAccess, PlayerChunk.Failure>> statusFuture = this.getStatusFutureUnchecked(ChunkStatus.FULL);
+        Either<IChunkAccess, PlayerChunk.Failure> either = (Either<IChunkAccess, PlayerChunk.Failure>) statusFuture.getNow(null);
+        return either == null ? null : (Chunk) either.left().orElse(null);
+    }
+    // CraftBukkit end
+
     public CompletableFuture<Either<IChunkAccess, PlayerChunk.Failure>> getStatusFutureUnchecked(ChunkStatus chunkstatus) {
         CompletableFuture<Either<IChunkAccess, PlayerChunk.Failure>> completablefuture = (CompletableFuture) this.statusFutures.get(chunkstatus.c());
 
@@ -79,9 +88,9 @@
     @Nullable
     public Chunk getChunk() {
         CompletableFuture<Either<Chunk, PlayerChunk.Failure>> completablefuture = this.a();
-        Either<Chunk, PlayerChunk.Failure> either = (Either) completablefuture.getNow((Object) null);
+        Either<Chunk, PlayerChunk.Failure> either = (Either) completablefuture.getNow(null); // CraftBukkit - decompile error
 
-        return either == null ? null : (Chunk) either.left().orElse((Object) null);
+        return either == null ? null : (Chunk) either.left().orElse(null); // CraftBukkit - decompile error
     }
 
     @Nullable
@@ -210,7 +219,7 @@
         CompletableFuture<Either<IChunkAccess, PlayerChunk.Failure>> completablefuture = (CompletableFuture) this.statusFutures.get(i);
 
         if (completablefuture != null) {
-            Either<IChunkAccess, PlayerChunk.Failure> either = (Either) completablefuture.getNow((Object) null);
+            Either<IChunkAccess, PlayerChunk.Failure> either = (Either) completablefuture.getNow(null); // CraftBukkit - decompile error
 
             if (either == null || either.left().isPresent()) {
                 return completablefuture;
@@ -265,6 +274,30 @@
         boolean flag1 = this.ticketLevel <= PlayerChunkMap.GOLDEN_TICKET;
         PlayerChunk.State playerchunk_state = getChunkState(this.oldTicketLevel);
         PlayerChunk.State playerchunk_state1 = getChunkState(this.ticketLevel);
+        // CraftBukkit start
+        // ChunkUnloadEvent: Called before the chunk is unloaded: isChunkLoaded is still true and chunk can still be modified by plugins.
+        if (playerchunk_state.isAtLeast(PlayerChunk.State.BORDER) && !playerchunk_state1.isAtLeast(PlayerChunk.State.BORDER)) {
+            this.getStatusFutureUnchecked(ChunkStatus.FULL).thenAccept((either) -> {
+                Chunk chunk = (Chunk)either.left().orElse(null);
+                if (chunk != null) {
+                    playerchunkmap.callbackExecutor.execute(() -> {
+                        // Minecraft will apply the chunks tick lists to the world once the chunk got loaded, and then store the tick
+                        // lists again inside the chunk once the chunk becomes inaccessible and set the chunk's needsSaving flag.
+                        // These actions may however happen deferred, so we manually set the needsSaving flag already here.
+                        chunk.setNeedsSaving(true);
+                        chunk.unloadCallback();
+                    });
+                }
+            }).exceptionally((throwable) -> {
+                // ensure exceptions are printed, by default this is not the case
+                MinecraftServer.LOGGER.fatal("Failed to schedule unload callback for chunk " + PlayerChunk.this.location, throwable);
+                return null;
+            });
+
+            // Run callback right away if the future was already done
+            playerchunkmap.callbackExecutor.run();
+        }
+        // CraftBukkit end
         CompletableFuture completablefuture;
 
         if (flag) {
@@ -296,7 +329,7 @@
         if (flag2 && !flag3) {
             completablefuture = this.fullChunkFuture;
             this.fullChunkFuture = PlayerChunk.UNLOADED_CHUNK_FUTURE;
-            this.a(completablefuture.thenApply((either1) -> {
+            this.a(((CompletableFuture<Either<Chunk, PlayerChunk.Failure>>) completablefuture).thenApply((either1) -> { // CraftBukkit - decompile error
                 playerchunkmap.getClass();
                 return either1.ifLeft(playerchunkmap::a);
             }));
@@ -334,6 +367,26 @@
 
         this.v.a(this.location, this::k, this.ticketLevel, this::d);
         this.oldTicketLevel = this.ticketLevel;
+        // CraftBukkit start
+        // ChunkLoadEvent: Called after the chunk is loaded: isChunkLoaded returns true and chunk is ready to be modified by plugins.
+        if (!playerchunk_state.isAtLeast(PlayerChunk.State.BORDER) && playerchunk_state1.isAtLeast(PlayerChunk.State.BORDER)) {
+            this.getStatusFutureUnchecked(ChunkStatus.FULL).thenAccept((either) -> {
+                Chunk chunk = (Chunk)either.left().orElse(null);
+                if (chunk != null) {
+                    playerchunkmap.callbackExecutor.execute(() -> {
+                        chunk.loadCallback();
+                    });
+                }
+            }).exceptionally((throwable) -> {
+                // ensure exceptions are printed, by default this is not the case
+                MinecraftServer.LOGGER.fatal("Failed to schedule load callback for chunk " + PlayerChunk.this.location, throwable);
+                return null;
+            });
+
+            // Run callback right away if the future was already done
+            playerchunkmap.callbackExecutor.run();
+        }
+        // CraftBukkit end
     }
 
     public static ChunkStatus getChunkStatus(int i) {