PaperMC/nms-patches/BlockTrapdoor.patch

--- a/net/minecraft/server/BlockTrapdoor.java
+++ b/net/minecraft/server/BlockTrapdoor.java
@@ -1,6 +1,7 @@
 package net.minecraft.server;
 
 import javax.annotation.Nullable;
+import org.bukkit.event.block.BlockRedstoneEvent; // CraftBukkit
 
 public class BlockTrapdoor extends BlockFacingHorizontal implements IFluidSource, IFluidContainer {
 
@@ -88,6 +89,19 @@
             boolean flag = world.isBlockIndirectlyPowered(blockposition);
 
             if (flag != (Boolean) iblockdata.get(BlockTrapdoor.c)) {
+                // CraftBukkit start
+                org.bukkit.World bworld = world.getWorld();
+                org.bukkit.block.Block bblock = bworld.getBlockAt(blockposition.getX(), blockposition.getY(), blockposition.getZ());
+
+                int power = bblock.getBlockPower();
+                int oldPower = (Boolean) iblockdata.get(OPEN) ? 15 : 0;
+
+                if (oldPower == 0 ^ power == 0 || block.getBlockData().isPowerSource()) {
+                    BlockRedstoneEvent eventRedstone = new BlockRedstoneEvent(bblock, oldPower, power);
+                    world.getServer().getPluginManager().callEvent(eventRedstone);
+                    flag = eventRedstone.getNewCurrent() > 0;
+                }
+                // CraftBukkit end
                 if ((Boolean) iblockdata.get(BlockTrapdoor.OPEN) != flag) {
                     iblockdata = (IBlockData) iblockdata.set(BlockTrapdoor.OPEN, flag);
                     this.a((EntityHuman) null, world, blockposition, flag);