Added a ##tag parser Pattern. gives a random combination using the blocks from the tag with an equal distribution.

worldedit-core/src/main/java/com/sk89q/worldedit/command/PatternCommands.java

@@ -268,7 +268,7 @@ public class PatternCommands extends MethodCommands {
             min = 1,
             max = 1
     )
-    public Pattern data(Actor actor, LocalSession session, Extent extent, BaseBiome biome) {
+    public Pattern biome(Actor actor, LocalSession session, Extent extent, BaseBiome biome) {
         return new BiomePattern(extent, biome);
     }
 

worldedit-core/src/main/java/com/sk89q/worldedit/extension/factory/PatternFactory.java

@@ -20,6 +20,7 @@
 package com.sk89q.worldedit.extension.factory;
 
 import com.sk89q.worldedit.WorldEdit;
+import com.sk89q.worldedit.extension.factory.parser.pattern.BlockCategoryPatternParser;
 import com.sk89q.worldedit.extension.factory.parser.pattern.ClipboardPatternParser;
 import com.sk89q.worldedit.extension.factory.parser.pattern.DefaultPatternParser;
 import com.sk89q.worldedit.extension.factory.parser.pattern.RandomPatternParser;
@@ -47,6 +48,7 @@ public final class PatternFactory extends AbstractFactory<Pattern> {
 //        register(new ClipboardPatternParser(worldEdit));
 //        register(new SingleBlockPatternParser(worldEdit));
 //        register(new RandomPatternParser(worldEdit));
+        register(new BlockCategoryPatternParser(worldEdit));
         register(new DefaultPatternParser(worldEdit));
     }
 

worldedit-core/src/main/java/com/sk89q/worldedit/extension/factory/parser/pattern/BlockCategoryPatternParser.java

@@ -0,0 +1,63 @@
+/*
+ * WorldEdit, a Minecraft world manipulation toolkit
+ * Copyright (C) sk89q <http://www.sk89q.com>
+ * Copyright (C) WorldEdit team and contributors
+ *
+ * This program is free software: you can redistribute it and/or modify it
+ * under the terms of the GNU Lesser General Public License as published by the
+ * Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public License
+ * for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public License
+ * along with this program. If not, see <http://www.gnu.org/licenses/>.
+ */
+
+package com.sk89q.worldedit.extension.factory.parser.pattern;
+
+import com.sk89q.worldedit.WorldEdit;
+import com.sk89q.worldedit.extension.input.InputParseException;
+import com.sk89q.worldedit.extension.input.ParserContext;
+import com.sk89q.worldedit.function.pattern.BlockPattern;
+import com.sk89q.worldedit.function.pattern.Pattern;
+import com.sk89q.worldedit.function.pattern.RandomPattern;
+import com.sk89q.worldedit.internal.registry.InputParser;
+import com.sk89q.worldedit.world.block.BlockCategory;
+import com.sk89q.worldedit.world.block.BlockType;
+
+import java.util.List;
+import java.util.stream.Collectors;
+
+public class BlockCategoryPatternParser extends InputParser<Pattern> {
+
+    public BlockCategoryPatternParser(WorldEdit worldEdit) {
+        super(worldEdit);
+    }
+
+    @Override
+    public List<String> getSuggestions() {
+        return BlockCategory.REGISTRY.keySet().stream().map(str -> "##" + str).collect(Collectors.toList());
+    }
+
+    @Override
+    public Pattern parseFromInput(String input, ParserContext context) throws InputParseException {
+        if(!input.startsWith("##")) {
+            return null;
+        }
+        BlockCategory category = BlockCategory.REGISTRY.get(input.substring(2).toLowerCase());
+        if (category == null) {
+            throw new InputParseException("Unknown block tag: " + input.substring(2));
+        }
+        RandomPattern randomPattern = new RandomPattern();
+
+        for (BlockType blockType : category.getAll()) {
+            randomPattern.add(new BlockPattern(blockType.getDefaultState()), 1.0 / category.getAll().size());
+        }
+
+        return randomPattern;
+    }
+}

worldedit-core/src/main/java/com/sk89q/worldedit/extent/world/ChunkLoadingExtent.java

@@ -63,6 +63,9 @@ public class ChunkLoadingExtent extends AbstractDelegateExtent {
     @Override
     public <B extends BlockStateHolder<B>> boolean setBlock(BlockVector3 location, B block) throws WorldEditException {
         world.checkLoadedChunk(location);
+        if (enabled) {
+            world.checkLoadedChunk(location);
+        }
         return super.setBlock(location, block);
     }
 }