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

--- a/net/minecraft/world/level/block/BlockLever.java
+++ b/net/minecraft/world/level/block/BlockLever.java
@@ -25,6 +25,8 @@
 import net.minecraft.world.phys.shapes.VoxelShape;
 import net.minecraft.world.phys.shapes.VoxelShapeCollision;
 
+import org.bukkit.event.block.BlockRedstoneEvent; // CraftBukkit
+
 public class BlockLever extends BlockAttachable {
 
     public static final BlockStateBoolean POWERED = BlockProperties.POWERED;
@@ -92,6 +94,20 @@
 
             return EnumInteractionResult.SUCCESS;
         } else {
+            // CraftBukkit start - Interact Lever
+            boolean powered = iblockdata.get(BlockLever.POWERED); // Old powered state
+            org.bukkit.block.Block block = world.getWorld().getBlockAt(blockposition.getX(), blockposition.getY(), blockposition.getZ());
+            int old = (powered) ? 15 : 0;
+            int current = (!powered) ? 15 : 0;
+
+            BlockRedstoneEvent eventRedstone = new BlockRedstoneEvent(block, old, current);
+            world.getCraftServer().getPluginManager().callEvent(eventRedstone);
+
+            if ((eventRedstone.getNewCurrent() > 0) != (!powered)) {
+                return EnumInteractionResult.SUCCESS;
+            }
+            // CraftBukkit end
+
             iblockdata1 = this.d(iblockdata, world, blockposition);
             float f = (Boolean) iblockdata1.get(BlockLever.POWERED) ? 0.6F : 0.5F;