craftbukkit/nms-patches/net/minecraft/world/level/redstone/DefaultRedstoneWireEvaluator.patch

--- a/net/minecraft/world/level/redstone/DefaultRedstoneWireEvaluator.java
+++ b/net/minecraft/world/level/redstone/DefaultRedstoneWireEvaluator.java
@@ -10,6 +10,11 @@
 import net.minecraft.world.level.block.BlockRedstoneWire;
 import net.minecraft.world.level.block.state.IBlockData;
 
+// CraftBukkit start
+import org.bukkit.craftbukkit.block.CraftBlock;
+import org.bukkit.event.block.BlockRedstoneEvent;
+// CraftBukkit end
+
 public class DefaultRedstoneWireEvaluator extends RedstoneWireEvaluator {
 
     public DefaultRedstoneWireEvaluator(BlockRedstoneWire blockredstonewire) {
@@ -20,7 +25,16 @@
     public void updatePowerStrength(World world, BlockPosition blockposition, IBlockData iblockdata, @Nullable Orientation orientation, boolean flag) {
         int i = this.calculateTargetStrength(world, blockposition);
 
-        if ((Integer) iblockdata.getValue(BlockRedstoneWire.POWER) != i) {
+        // CraftBukkit start
+        int oldPower = iblockdata.getValue(BlockRedstoneWire.POWER);
+        if (oldPower != i) {
+            BlockRedstoneEvent event = new BlockRedstoneEvent(CraftBlock.at(world, blockposition), oldPower, i);
+            world.getCraftServer().getPluginManager().callEvent(event);
+
+            i = event.getNewCurrent();
+        }
+        if (oldPower != i) {
+            // CraftBukkit end
             if (world.getBlockState(blockposition) == iblockdata) {
                 world.setBlock(blockposition, (IBlockData) iblockdata.setValue(BlockRedstoneWire.POWER, i), 2);
             }