Fixes #452

- ChunkSections containing only air are technically null according to NMS Chunks
- Therefore if we're replacing air, we should ignore the result of get.hasSection(layer) by using "full = true" as it returns false if the chunksection is only air
- We also then need to ensure that the masks correctly identify that the block is "air"

worldedit-core/src/main/java/com/boydti/fawe/beta/implementation/queue/ParallelQueueExtent.java

@@ -162,7 +162,8 @@ public class ParallelQueueExtent extends PassthroughExtent implements IQueueWrap
     @Override
     public int replaceBlocks(Region region, Mask mask, Pattern pattern)
         throws MaxChangedBlocksException {
-        return this.changes = apply(region, mask.toFilter(pattern), false).getBlocksApplied();
+        boolean full = mask.replacesAir();
+        return this.changes = apply(region, mask.toFilter(pattern), full).getBlocksApplied();
     }
 
     @Override

worldedit-core/src/main/java/com/sk89q/worldedit/function/mask/BlockMask.java

@@ -189,7 +189,15 @@ public class BlockMask extends ABlockMask {
 
     @Override
     public boolean test(Extent extent, BlockVector3 vector) {
-        return ordinals[vector.getOrdinal(extent)];
+        int test = vector.getOrdinal(extent);
+        return ordinals[test] || replacesAir() && test == 0;
+    }
+
+    @Override
+    public boolean replacesAir() {
+        return ordinals[BlockTypes.AIR.getDefaultState().getOrdinal()]
+            || ordinals[BlockTypes.CAVE_AIR.getDefaultState().getOrdinal()]
+            || ordinals[BlockTypes.VOID_AIR.getDefaultState().getOrdinal()];
     }
 
     @Override

worldedit-core/src/main/java/com/sk89q/worldedit/function/mask/BlockStateMask.java

@@ -26,6 +26,8 @@ import com.sk89q.worldedit.math.BlockVector3;
 import com.sk89q.worldedit.registry.state.Property;
 import com.sk89q.worldedit.world.block.BlockState;
 import com.sk89q.worldedit.world.block.BlockType;
+import com.sk89q.worldedit.world.block.BlockTypes;
+
 import java.util.Map;
 import javax.annotation.Nullable;
 
@@ -65,6 +67,11 @@ public class BlockStateMask extends AbstractExtentMask {
                 .allMatch(entry -> block.getState(entry.getKey()) == entry.getValue());
     }
 
+    @Override
+    public boolean replacesAir() {
+        return test(BlockTypes.AIR.getDefaultState()) || test(BlockTypes.CAVE_AIR.getDefaultState()) || test(BlockTypes.VOID_AIR.getDefaultState());
+    }
+
     @Nullable
     @Override
     public Mask2D toMask2D() {

worldedit-core/src/main/java/com/sk89q/worldedit/function/mask/BlockTypeMask.java

@@ -43,6 +43,7 @@ import org.jetbrains.annotations.NotNull;
 public class BlockTypeMask extends AbstractExtentMask {
 
     private final boolean[] types;
+    private boolean hasAir;
 
     /**
      * Create a new block mask.
@@ -63,7 +64,9 @@ public class BlockTypeMask extends AbstractExtentMask {
     public BlockTypeMask(Extent extent, @NotNull BlockType... block) {
         super(extent);
         this.types = new boolean[BlockTypes.size()];
-        for (BlockType type : block) this.types[type.getInternalId()] = true;
+        for (BlockType type : block) {
+            add(type);
+        }
     }
 
     /**
@@ -76,9 +79,6 @@ public class BlockTypeMask extends AbstractExtentMask {
         for (BlockType type : blocks) {
             add(type);
         }
-        for (BlockType type : blocks) {
-            this.types[type.getInternalId()] = true;
-        }
     }
 
     /**
@@ -88,6 +88,9 @@ public class BlockTypeMask extends AbstractExtentMask {
      */
     public void add(@NotNull BlockType... block) {
         for (BlockType type : block) {
+            if (!hasAir && (type == BlockTypes.AIR || type == BlockTypes.CAVE_AIR || type == BlockTypes.VOID_AIR)) {
+                hasAir = true;
+            }
             this.types[type.getInternalId()] = true;
         }
     }
@@ -110,6 +113,11 @@ public class BlockTypeMask extends AbstractExtentMask {
         return test(vector.getBlock(extent).getBlockType());
     }
 
+    @Override
+    public boolean replacesAir() {
+        return hasAir;
+    }
+
     public boolean test(BlockType block) {
         return types[block.getInternalId()];
     }

worldedit-core/src/main/java/com/sk89q/worldedit/function/mask/Mask.java

@@ -123,4 +123,8 @@ public interface Mask {
             }
         };
     }
+
+    default boolean replacesAir() {
+        return false;
+    }
 }

worldedit-core/src/main/java/com/sk89q/worldedit/function/mask/SingleBlockStateMask.java

@@ -1,13 +1,12 @@
 package com.sk89q.worldedit.function.mask;
 
-import com.boydti.fawe.Fawe;
 import com.sk89q.worldedit.extent.Extent;
 import com.sk89q.worldedit.math.BlockVector3;
 import com.sk89q.worldedit.world.block.BlockState;
-import com.sk89q.worldedit.world.block.BlockStateHolder;
 
 public class SingleBlockStateMask extends ABlockMask {
     private final char ordinal;
+    private final boolean isAir;
 
     public BlockState getBlockState() {
         return BlockState.getFromOrdinal(ordinal);
@@ -15,12 +14,14 @@ public class SingleBlockStateMask extends ABlockMask {
 
     public SingleBlockStateMask(Extent extent, BlockState state) {
         super(extent);
+        isAir = state.isAir();
         this.ordinal = state.getOrdinalChar();
     }
 
     @Override
     public boolean test(Extent extent, BlockVector3 vector) {
-        return ordinal == vector.getOrdinal(extent);
+        int test = vector.getOrdinal(extent);
+        return ordinal == test || isAir && test == 0;
     }
 
     @Override
@@ -33,6 +34,11 @@ public class SingleBlockStateMask extends ABlockMask {
         return new InverseSingleBlockStateMask(getExtent(), BlockState.getFromOrdinal(ordinal));
     }
 
+    @Override
+    public boolean replacesAir() {
+        return isAir;
+    }
+
     @Override
     public Mask tryCombine(Mask mask) {
         if (mask instanceof ABlockMask) {

worldedit-core/src/main/java/com/sk89q/worldedit/function/mask/SingleBlockTypeMask.java

@@ -8,10 +8,12 @@ import com.sk89q.worldedit.world.block.BlockTypesCache;
 
 public class SingleBlockTypeMask extends ABlockMask {
     private final int internalId;
+    private final boolean isAir;
 
     public SingleBlockTypeMask(Extent extent, BlockType type) {
         super(extent);
-        this.internalId = type.getInternalId();
+        isAir = type == BlockTypes.AIR || type == BlockTypes.CAVE_AIR || type == BlockTypes.VOID_AIR;
+            this.internalId = type.getInternalId();
     }
 
     @Override
@@ -27,4 +29,9 @@ public class SingleBlockTypeMask extends ABlockMask {
     public BlockType getBlockType() {
         return BlockTypes.get(internalId);
     }
+
+    @Override
+    public boolean replacesAir() {
+        return isAir;
+    }
 }