PaperMC/paper-server/patches/sources/net/minecraft/server/level/DistanceManager.java.patch

--- a/net/minecraft/server/level/DistanceManager.java
+++ b/net/minecraft/server/level/DistanceManager.java
@@ -107,6 +_,12 @@
         }
 
         if (!this.chunksToUpdateFutures.isEmpty()) {
+            // CraftBukkit start - SPIGOT-7780: Call chunk unload events before updateHighestAllowedStatus
+            for (final ChunkHolder chunkHolder : this.chunksToUpdateFutures) {
+                chunkHolder.callEventIfUnloading(chunkMap);
+            }
+            // CraftBukkit end - SPIGOT-7780: Call chunk unload events before updateHighestAllowedStatus
+
             for (ChunkHolder chunkHolder : this.chunksToUpdateFutures) {
                 chunkHolder.updateHighestAllowedStatus(chunkMap);
             }
@@ -177,16 +_,42 @@
     public <T> void addRegionTicket(TicketType<T> type, ChunkPos pos, int distance, T value) {
         Ticket<T> ticket = new Ticket<>(type, ChunkLevel.byStatus(FullChunkStatus.FULL) - distance, value);
         long packedChunkPos = pos.toLong();
-        this.addTicket(packedChunkPos, ticket);
+        this.addTicket(packedChunkPos, ticket); // Paper - diff on change above
         this.tickingTicketsTracker.addTicket(packedChunkPos, ticket);
     }
 
     public <T> void removeRegionTicket(TicketType<T> type, ChunkPos pos, int distance, T value) {
         Ticket<T> ticket = new Ticket<>(type, ChunkLevel.byStatus(FullChunkStatus.FULL) - distance, value);
         long packedChunkPos = pos.toLong();
+        this.removeTicket(packedChunkPos, ticket); // Paper - diff on change above
+        this.tickingTicketsTracker.removeTicket(packedChunkPos, ticket);
+    }
+
+    // Paper start
+    public boolean addPluginRegionTicket(final ChunkPos pos, final org.bukkit.plugin.Plugin value) {
+        Ticket<org.bukkit.plugin.Plugin> ticket = new Ticket<>(TicketType.PLUGIN_TICKET, ChunkLevel.byStatus(FullChunkStatus.FULL) - 2, value); // Copied from below and keep in-line with force loading, add at level 31
+        final long packedChunkPos = pos.toLong();
+        final Set<Ticket<?>> tickets = this.getTickets(packedChunkPos);
+        if (tickets.contains(ticket)) {
+            return false;
+        }
+        this.addTicket(packedChunkPos, ticket);
+        this.tickingTicketsTracker.addTicket(packedChunkPos, ticket);
+        return true;
+    }
+
+    public boolean removePluginRegionTicket(final ChunkPos pos, final org.bukkit.plugin.Plugin value) {
+        Ticket<org.bukkit.plugin.Plugin> ticket = new Ticket<>(TicketType.PLUGIN_TICKET, ChunkLevel.byStatus(FullChunkStatus.FULL) - 2, value); // Copied from below and keep in-line with force loading, add at level 31
+        final long packedChunkPos = pos.toLong();
+        final Set<Ticket<?>> tickets = this.tickets.get(packedChunkPos); // Don't use getTickets, we don't want to create a new set
+        if (tickets == null || !tickets.contains(ticket)) {
+            return false;
+        }
         this.removeTicket(packedChunkPos, ticket);
         this.tickingTicketsTracker.removeTicket(packedChunkPos, ticket);
+        return true;
     }
+    // Paper end
 
     private SortedArraySet<Ticket<?>> getTickets(long chunkPos) {
         return this.tickets.computeIfAbsent(chunkPos, l -> SortedArraySet.create(4));
@@ -217,8 +_,10 @@
         ChunkPos chunkPos = sectionPos.chunk();
         long packedChunkPos = chunkPos.toLong();
         ObjectSet<ServerPlayer> set = this.playersPerChunk.get(packedChunkPos);
-        set.remove(player);
-        if (set.isEmpty()) {
+        // Paper start - some state corruption happens here, don't crash, clean up gracefully
+        if (set != null) set.remove(player);
+        if (set == null || set.isEmpty()) {
+        // Paper end - some state corruption happens here, don't crash, clean up gracefully
             this.playersPerChunk.remove(packedChunkPos);
             this.naturalSpawnChunkCounter.update(packedChunkPos, Integer.MAX_VALUE, false);
             this.playerTicketManager.update(packedChunkPos, Integer.MAX_VALUE, false);
@@ -299,7 +_,7 @@
     }
 
     public void removeTicketsOnClosing() {
-        ImmutableSet<TicketType<?>> set = ImmutableSet.of(TicketType.UNKNOWN);
+        ImmutableSet<TicketType<?>> set = ImmutableSet.of(TicketType.UNKNOWN, TicketType.POST_TELEPORT, TicketType.FUTURE_AWAIT); // Paper - add additional tickets to preserve
         ObjectIterator<Entry<SortedArraySet<Ticket<?>>>> objectIterator = this.tickets.long2ObjectEntrySet().fastIterator();
 
         while (objectIterator.hasNext()) {
@@ -329,6 +_,26 @@
     public boolean hasTickets() {
         return !this.tickets.isEmpty();
     }
+
+    // CraftBukkit start
+    public <T> void removeAllTicketsFor(TicketType<T> ticketType, int ticketLevel, T ticketIdentifier) {
+        Ticket<T> target = new Ticket<>(ticketType, ticketLevel, ticketIdentifier);
+
+        for (java.util.Iterator<Entry<SortedArraySet<Ticket<?>>>> iterator = this.tickets.long2ObjectEntrySet().fastIterator(); iterator.hasNext();) {
+            Entry<SortedArraySet<Ticket<?>>> entry = iterator.next();
+            SortedArraySet<Ticket<?>> tickets = entry.getValue();
+            if (tickets.remove(target)) {
+                // copied from removeTicket
+                this.ticketTracker.update(entry.getLongKey(), DistanceManager.getTicketLevelAt(tickets), false);
+
+                // can't use entry after it's removed
+                if (tickets.isEmpty()) {
+                    iterator.remove();
+                }
+            }
+        }
+    }
+    // CraftBukkit end
 
     class ChunkTicketTracker extends ChunkTracker {
         private static final int MAX_LEVEL = ChunkLevel.MAX_LEVEL + 1;