From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
From: Aikar <aikar@aikar.co>
Date: Thu, 23 Apr 2020 01:36:39 -0400
Subject: [PATCH] Don't fire BlockFade on worldgen threads

Caused a deadlock

diff --git a/src/main/java/net/minecraft/world/level/block/BlockFire.java b/src/main/java/net/minecraft/world/level/block/BlockFire.java
index 5ef38414d87fbce453e3ab11579c89a8ff089ae0..e6ea1d29c7f3f4cb6039df0e35c8db94b6f38c3e 100644
--- a/src/main/java/net/minecraft/world/level/block/BlockFire.java
+++ b/src/main/java/net/minecraft/world/level/block/BlockFire.java
@@ -94,6 +94,7 @@ public class BlockFire extends BlockFireAbstract {
     @Override
     public IBlockData updateState(IBlockData iblockdata, EnumDirection enumdirection, IBlockData iblockdata1, GeneratorAccess generatoraccess, BlockPosition blockposition, BlockPosition blockposition1) {
         // CraftBukkit start
+        if (!(generatoraccess instanceof WorldServer)) return this.canPlace(iblockdata, generatoraccess, blockposition) ? (IBlockData) this.a(generatoraccess, blockposition, (Integer) iblockdata.get(BlockFire.AGE)) : Blocks.AIR.getBlockData(); // Paper - don't fire events in world generation
         if (!this.canPlace(iblockdata, generatoraccess, blockposition)) {
             // Suppress during worldgen
             if (!(generatoraccess instanceof World)) {
@@ -109,7 +110,7 @@ public class BlockFire extends BlockFireAbstract {
                 return blockState.getHandle();
             }
         }
-        return this.a(generatoraccess, blockposition, (Integer) iblockdata.get(BlockFire.AGE));
+        return this.a(generatoraccess, blockposition, (Integer) iblockdata.get(BlockFire.AGE)); // Paper - diff on change, see "don't fire events in world generation"
         // CraftBukkit end
     }