PaperMC/nms-patches/WorldGenTreeProvider.patch

--- a/net/minecraft/server/WorldGenTreeProvider.java
+++ b/net/minecraft/server/WorldGenTreeProvider.java
@@ -2,6 +2,7 @@
 
 import java.util.Random;
 import javax.annotation.Nullable;
+import org.bukkit.TreeType; // CraftBukkit
 
 public abstract class WorldGenTreeProvider {
 
@@ -16,6 +17,25 @@
         if (worldgentreeabstract == null) {
             return false;
         } else {
+            // CraftBukkit start
+            if (worldgentreeabstract instanceof WorldGenAcaciaTree) {
+                BlockSapling.treeType = TreeType.ACACIA;
+            } else if (worldgentreeabstract instanceof WorldGenBigTree) {
+                BlockSapling.treeType = TreeType.BIG_TREE;
+            } else if (worldgentreeabstract instanceof WorldGenForest) {
+                BlockSapling.treeType = TreeType.BIRCH;
+            } else if (worldgentreeabstract instanceof WorldGenForestTree) {
+                BlockSapling.treeType = TreeType.DARK_OAK;
+            } else if (worldgentreeabstract instanceof WorldGenTaiga1) {
+                BlockSapling.treeType = TreeType.REDWOOD;
+            } else if (worldgentreeabstract instanceof WorldGenTaiga2) {
+                BlockSapling.treeType = TreeType.REDWOOD;
+            } else if (worldgentreeabstract instanceof WorldGenTrees) {
+                BlockSapling.treeType = TreeType.TREE;
+            } else {
+                throw new IllegalArgumentException("Unknown tree generator " + worldgentreeabstract);
+            }
+            // CraftBukkit end
             generatoraccess.setTypeAndData(blockposition, Blocks.AIR.getBlockData(), 4);
             if (worldgentreeabstract.generate(generatoraccess, generatoraccess.getChunkProvider().getChunkGenerator(), random, blockposition, WorldGenFeatureConfiguration.e)) {
                 return true;