PaperMC/paper-server/nms-patches/net/minecraft/world/level/block/BlockRedstoneWire.patch

--- a/net/minecraft/world/level/block/BlockRedstoneWire.java
+++ b/net/minecraft/world/level/block/BlockRedstoneWire.java
@@ -37,6 +37,8 @@
 import net.minecraft.world.phys.shapes.VoxelShapeCollision;
 import net.minecraft.world.phys.shapes.VoxelShapes;
 
+import org.bukkit.event.block.BlockRedstoneEvent; // CraftBukkit
+
 public class BlockRedstoneWire extends Block {
 
     public static final BlockStateEnum<BlockPropertyRedstoneSide> NORTH = BlockProperties.NORTH_REDSTONE;
@@ -257,7 +259,16 @@
     private void updatePowerStrength(World world, BlockPosition blockposition, IBlockData iblockdata) {
         int i = this.calculateTargetStrength(world, blockposition);
 
-        if ((Integer) iblockdata.getValue(BlockRedstoneWire.POWER) != i) {
+        // CraftBukkit start
+        int oldPower = (Integer) iblockdata.getValue(BlockRedstoneWire.POWER);
+        if (oldPower != i) {
+            BlockRedstoneEvent event = new BlockRedstoneEvent(world.getWorld().getBlockAt(blockposition.getX(), blockposition.getY(), blockposition.getZ()), 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);
             }