Implement World#regenerateChunk (#7425)

Co-authored-by: Jason Penilla <11360596+jpenilla@users.noreply.github.com>

patches/api/Implement-regenerateChunk.patch

@@ -0,0 +1,21 @@
+From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
+From: Nassim Jahnke <nassim@njahnke.dev>
+Date: Sat, 5 Feb 2022 20:25:28 +0100
+Subject: [PATCH] Implement regenerateChunk
+
+
+diff --git a/src/main/java/org/bukkit/World.java b/src/main/java/org/bukkit/World.java
+index 0000000000000000000000000000000000000000..0000000000000000000000000000000000000000 100644
+--- a/src/main/java/org/bukkit/World.java
++++ b/src/main/java/org/bukkit/World.java
+@@ -0,0 +0,0 @@ public interface World extends RegionAccessor, WorldInfo, PluginMessageRecipient
+      * @return Whether the chunk was actually regenerated
+      *
+      * @deprecated regenerating a single chunk is not likely to produce the same
+-     * chunk as before as terrain decoration may be spread across chunks. Use of
+-     * this method should be avoided as it is known to produce buggy results.
++     * chunk as before as terrain decoration may be spread across chunks. It may
++     * or may not change blocks in the adjacent chunks as well.
+      */
+     @Deprecated
+     public boolean regenerateChunk(int x, int z);

patches/server/Implement-regenerateChunk.patch

@@ -0,0 +1,97 @@
+From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
+From: Nassim Jahnke <nassim@njahnke.dev>
+Date: Mon, 31 Jan 2022 11:21:50 +0100
+Subject: [PATCH] Implement regenerateChunk
+
+Co-authored-by: Jason Penilla <11360596+jpenilla@users.noreply.github.com>
+
+diff --git a/src/main/java/org/bukkit/craftbukkit/CraftWorld.java b/src/main/java/org/bukkit/craftbukkit/CraftWorld.java
+index 0000000000000000000000000000000000000000..0000000000000000000000000000000000000000 100644
+--- a/src/main/java/org/bukkit/craftbukkit/CraftWorld.java
++++ b/src/main/java/org/bukkit/craftbukkit/CraftWorld.java
+@@ -0,0 +0,0 @@ import org.bukkit.util.Vector;
+ 
+ public class CraftWorld extends CraftRegionAccessor implements World {
+     public static final int CUSTOM_DIMENSION_OFFSET = 10;
++    private static final ChunkStatus[] REGEN_CHUNK_STATUSES = {ChunkStatus.BIOMES, ChunkStatus.NOISE, ChunkStatus.SURFACE, ChunkStatus.CARVERS, ChunkStatus.LIQUID_CARVERS, ChunkStatus.FEATURES}; // Paper - implement regenerate chunk method
+ 
+     private final ServerLevel world;
+     private WorldBorder worldBorder;
+@@ -0,0 +0,0 @@ public class CraftWorld extends CraftRegionAccessor implements World {
+     @Override
+     public boolean regenerateChunk(int x, int z) {
+         org.spigotmc.AsyncCatcher.catchOp("chunk regenerate"); // Spigot
+-        throw new UnsupportedOperationException("Not supported in this Minecraft version! Unless you can fix it, this is not a bug :)");
+-        /*
+-        if (!unloadChunk0(x, z, false)) {
+-            return false;
+-        }
+-
+-        final long chunkKey = ChunkCoordIntPair.pair(x, z);
+-        world.getChunkProvider().unloadQueue.remove(chunkKey);
++        // Paper start - implement regenerateChunk method
++        final ServerLevel serverLevel = this.world;
++        final net.minecraft.server.level.ServerChunkCache serverChunkCache = serverLevel.getChunkSource();
++        final ChunkPos chunkPos = new ChunkPos(x, z);
++        final net.minecraft.world.level.chunk.LevelChunk levelChunk = serverChunkCache.getChunk(chunkPos.x, chunkPos.z, true);
++        for (final BlockPos blockPos : BlockPos.betweenClosed(chunkPos.getMinBlockX(), serverLevel.getMinBuildHeight(), chunkPos.getMinBlockZ(), chunkPos.getMaxBlockX(), serverLevel.getMaxBuildHeight() - 1, chunkPos.getMaxBlockZ())) {
++            levelChunk.removeBlockEntity(blockPos);
++            serverLevel.setBlock(blockPos, Blocks.AIR.defaultBlockState(), 16);
++        }
++
++        for (final ChunkStatus chunkStatus : REGEN_CHUNK_STATUSES) {
++            final List<ChunkAccess> list = new ArrayList<>();
++            final int range = Math.max(1, chunkStatus.getRange());
++            for (int chunkX = chunkPos.z - range; chunkX <= chunkPos.z + range; chunkX++) {
++                for (int chunkZ = chunkPos.x - range; chunkZ <= chunkPos.x + range; chunkZ++) {
++                    ChunkAccess chunkAccess = serverChunkCache.getChunk(chunkZ, chunkX, chunkStatus.getParent(), true);
++                    if (chunkAccess instanceof ImposterProtoChunk accessProtoChunk) {
++                        chunkAccess = new ImposterProtoChunk(accessProtoChunk.getWrapped(), true);
++                    } else if (chunkAccess instanceof net.minecraft.world.level.chunk.LevelChunk accessLevelChunk) {
++                        chunkAccess = new ImposterProtoChunk(accessLevelChunk, true);
++                    }
++                    list.add(chunkAccess);
++                }
++            }
+ 
+-        net.minecraft.server.Chunk chunk = world.getChunkProvider().generateChunk(x, z);
+-        PlayerChunk playerChunk = world.getPlayerChunkMap().getChunk(x, z);
+-        if (playerChunk != null) {
+-            playerChunk.chunk = chunk;
++            final com.mojang.datafixers.util.Either<ChunkAccess, ChunkHolder.ChunkLoadingFailure> either = chunkStatus.generate(
++                Runnable::run,
++                serverLevel,
++                serverChunkCache.getGenerator(),
++                serverLevel.getStructureManager(),
++                serverChunkCache.getLightEngine(),
++                chunk -> {
++                    throw new UnsupportedOperationException("Not creating full chunks here");
++                },
++                list,
++                true
++            ).join();
++            if (chunkStatus == ChunkStatus.NOISE) {
++                either.left().ifPresent(chunk -> net.minecraft.world.level.levelgen.Heightmap.primeHeightmaps(chunk, ChunkStatus.POST_FEATURES));
++            }
+         }
+ 
+-        if (chunk != null) {
+-            refreshChunk(x, z);
++        for (final BlockPos blockPos : BlockPos.betweenClosed(chunkPos.getMinBlockX(), serverLevel.getMinBuildHeight(), chunkPos.getMinBlockZ(), chunkPos.getMaxBlockX(), serverLevel.getMaxBuildHeight() - 1, chunkPos.getMaxBlockZ())) {
++            serverChunkCache.blockChanged(blockPos);
+         }
+ 
+-        return chunk != null;
+-        */
++        final Set<ChunkPos> chunksToRelight = new HashSet<>(9);
++        for (int chunkX = chunkPos.x - 1; chunkX <= chunkPos.x + 1 ; chunkX++) {
++            for (int chunkZ = chunkPos.z - 1; chunkZ <= chunkPos.z + 1 ; chunkZ++) {
++                chunksToRelight.add(new ChunkPos(chunkX, chunkZ));
++            }
++        }
++        serverChunkCache.getLightEngine().relight(chunksToRelight, pos -> {}, relit -> {});
++        return true;
++        // Paper end
+     }
+ 
+     @Override

patches/server/Only-write-chunk-data-to-disk-if-it-serializes-witho.patch

@@ -7,6 +7,35 @@ Subject: [PATCH] Only write chunk data to disk if it serializes without
 This ensures at least a valid version of the chunk exists
 on disk, even if outdated
 
+diff --git a/src/main/java/net/minecraft/world/level/chunk/storage/RegionFile.java b/src/main/java/net/minecraft/world/level/chunk/storage/RegionFile.java
+index 0000000000000000000000000000000000000000..0000000000000000000000000000000000000000 100644
+--- a/src/main/java/net/minecraft/world/level/chunk/storage/RegionFile.java
++++ b/src/main/java/net/minecraft/world/level/chunk/storage/RegionFile.java
+@@ -0,0 +0,0 @@ public class RegionFile implements AutoCloseable {
+             this.pos = chunkcoordintpair;
+         }
+ 
++        // Paper start - don't write garbage data to disk if writing serialization fails
++        @Override
++        public void write(final int b) {
++            if (this.count > 500_000_000) {
++                throw new RegionFileStorage.RegionFileSizeException("Region file too large: " + this.count);
++            }
++            super.write(b);
++        }
++
++        @Override
++        public void write(final byte[] b, final int off, final int len) {
++            if (this.count + len > 500_000_000) {
++                throw new RegionFileStorage.RegionFileSizeException("Region file too large: " + (this.count + len));
++            }
++            super.write(b, off, len);
++        }
++        // Paper end
++
+         public void close() throws IOException {
+             ByteBuffer bytebuffer = ByteBuffer.wrap(this.buf, 0, this.count);
+ 
 diff --git a/src/main/java/net/minecraft/world/level/chunk/storage/RegionFileStorage.java b/src/main/java/net/minecraft/world/level/chunk/storage/RegionFileStorage.java
 index 0000000000000000000000000000000000000000..0000000000000000000000000000000000000000 100644
 --- a/src/main/java/net/minecraft/world/level/chunk/storage/RegionFileStorage.java
@@ -16,6 +45,12 @@ index 0000000000000000000000000000000000000000..00000000000000000000000000000000
                  regionfile.setStatus(pos.x, pos.z, ChunkSerializer.getStatus(nbt)); // Paper - cache status on disk
                  regionfile.setOversized(pos.x, pos.z, false); // Paper - We don't do this anymore, mojang stores differently, but clear old meta flag if it exists to get rid of our own meta file once last oversized is gone
 +                dataoutputstream.close(); // Paper - only write if successful
++            // Paper start - don't write garbage data to disk if writing serialization fails
++            } catch (RegionFileSizeException e) {
++                attempts = 5; // Don't retry
++                regionfile.clear(pos);
++                throw e;
++                // Paper end - don't write garbage data to disk if writing serialization fails
              } catch (Throwable throwable) {
                  if (dataoutputstream != null) {
                      try {
@@ -36,3 +71,17 @@ index 0000000000000000000000000000000000000000..00000000000000000000000000000000
          }
  
              // Paper start
+@@ -0,0 +0,0 @@ public class RegionFileStorage implements AutoCloseable {
+         }
+ 
+     }
++
++    // Paper start
++    public static final class RegionFileSizeException extends RuntimeException {
++
++        public RegionFileSizeException(String message) {
++            super(message);
++        }
++    }
++    // Paper end
+ }