fix: we should just always clone the region in ApplyTask (#3249)

- fixes #3231

Author: dordsor21

worldedit-core/src/main/java/com/fastasyncworldedit/core/queue/implementation/ApplyTask.java

@@ -23,6 +23,7 @@ class ApplyTask<F extends Filter> extends RecursiveAction implements Runnable {
     private static final int SHIFT_REDUCTION = 1;
 
     private final CommonState<F> commonState;
+    private final Region region;
     private final ApplyTask<F> before;
     private final int minChunkX;
     private final int minChunkZ;
@@ -39,7 +40,6 @@ public void run() {
 
     private record CommonState<F extends Filter>(
             F originalFilter,
-            Region region,
             ParallelQueueExtent parallelQueueExtent,
             ConcurrentMap<Thread, ThreadState<F>> stateCache,
             boolean full,
@@ -69,12 +69,12 @@ private ThreadState(SingleThreadQueueExtent queue, F filter) {
     ) {
         this.commonState = new CommonState<>(
                 filter,
-                region.clone(), // clone only once, assuming the filter doesn't modify that clone
                 parallelQueueExtent,
                 new ConcurrentHashMap<>(),
                 full,
                 faweExceptionReasonsUsed
         );
+        this.region = region.clone();
         this.before = null;
         final BlockVector3 minimumPoint = region.getMinimumPoint();
         this.minChunkX = minimumPoint.x() >> 4;
@@ -88,6 +88,7 @@ private ThreadState(SingleThreadQueueExtent queue, F filter) {
 
     private ApplyTask(
             final CommonState<F> commonState,
+            final Region region,
             final ApplyTask<F> before,
             final int minChunkX,
             final int maxChunkX,
@@ -96,6 +97,7 @@ private ApplyTask(
             final int higherShift
     ) {
         this.commonState = commonState;
+        this.region = region.clone();
         this.minChunkX = minChunkX;
         this.maxChunkX = maxChunkX;
         this.minChunkZ = minChunkZ;
@@ -120,14 +122,15 @@ protected void compute() {
                         processRegion(regionX, regionZ, this.shift);
                         continue;
                     }
-                    if (this.shift == 0 && !this.commonState.region.containsChunk(regionX, regionZ)) {
+                    if (this.shift == 0 && !this.region.containsChunk(regionX, regionZ)) {
                         // if shift == 0, region coords are chunk coords
                         continue; // chunks not intersecting with the region don't need a task
                     }
 
                     // creating more tasks will likely help parallelism as other threads aren't *that* busy
                     subtask = new ApplyTask<>(
                             this.commonState,
+                            this.region,
                             subtask,
                             regionX << this.shift,
                             ((regionX + 1) << this.shift) - 1,
@@ -166,7 +169,7 @@ private void processRegion(int regionX, int regionZ, int shift) {
         try {
             for (int chunkX = regionX << shift; chunkX <= ((regionX  + 1) << shift) - 1; chunkX++) {
                 for (int chunkZ = regionZ << shift; chunkZ <= ((regionZ  + 1) << shift) - 1; chunkZ++) {
-                    if (!this.commonState.region.containsChunk(chunkX, chunkZ)) {
+                    if (!this.region.containsChunk(chunkX, chunkZ)) {
                         continue; // chunks not intersecting with the region must not be processed
                     }
                     applyChunk(chunkX, chunkZ, state);
@@ -204,7 +207,7 @@ private void applyChunk(int chunkX, int chunkZ, ThreadState<F> state) {
             state.block = state.queue.apply(
                     state.block,
                     state.filter,
-                    this.commonState.region,
+                    this.region,
                     chunkX,
                     chunkZ,
                     this.commonState.full

worldedit-core/src/main/java/com/sk89q/worldedit/regions/ConvexPolyhedralRegion.java

@@ -89,13 +89,13 @@ public ConvexPolyhedralRegion(@Nullable World world) {
     public ConvexPolyhedralRegion(ConvexPolyhedralRegion region) {
         this(region.world);
         vertices.addAll(region.vertices);
-        triangles.addAll(region.triangles);
+        region.triangles.forEach(triangle -> triangles.add(triangle.clone()));
         vertexBacklog.addAll(region.vertexBacklog);
 
         minimumPoint = region.minimumPoint;
         maximumPoint = region.maximumPoint;
         centerAccum = region.centerAccum;
-        lastTriangle = region.lastTriangle;
+        lastTriangle = lastTriangle == null ? null : region.lastTriangle.clone();
     }
 
     /**

worldedit-core/src/main/java/com/sk89q/worldedit/regions/polyhedron/Triangle.java

@@ -105,6 +105,11 @@ public Triangle tag(String tag) {
         return this;
     }
 
+    @Override
+    public Triangle clone() {
+        return new Triangle(vertices[0], vertices[1], vertices[2]);
+    }
+
     @Override
     public String toString() {
         return tag + "(" + this.vertices[0] + "," + this.vertices[1] + "," + this.vertices[2] + ")";