PaperMC/nms-patches/EntityMushroomCow.patch

--- a/net/minecraft/server/EntityMushroomCow.java
+++ b/net/minecraft/server/EntityMushroomCow.java
@@ -2,6 +2,12 @@
 
 import javax.annotation.Nullable;
 
+// CraftBukkit start
+import org.bukkit.craftbukkit.event.CraftEventFactory;
+import org.bukkit.event.entity.EntityTransformEvent;
+import org.bukkit.event.player.PlayerShearEntityEvent;
+// CraftBukkit end
+
 public class EntityMushroomCow extends EntityCow {
 
     public EntityMushroomCow(World world) {
@@ -23,6 +29,14 @@
 
             return true;
         } else if (itemstack.getItem() == Items.SHEARS && this.getAge() >= 0) {
+            // CraftBukkit start
+            PlayerShearEntityEvent event = new PlayerShearEntityEvent((org.bukkit.entity.Player) entityhuman.getBukkitEntity(), this.getBukkitEntity());
+            this.world.getServer().getPluginManager().callEvent(event);
+
+            if (event.isCancelled()) {
+                return false;
+            }
+            // CraftBukkit end
             this.world.addParticle(Particles.u, this.locX, this.locY + (double) (this.length / 2.0F), this.locZ, 0.0D, 0.0D, 0.0D);
             if (!this.world.isClientSide) {
                 this.die();
@@ -35,6 +49,11 @@
                     entitycow.setCustomName(this.getCustomName());
                 }
 
+                // CraftBukkit start
+                if (CraftEventFactory.callEntityTransformEvent(this, entitycow, EntityTransformEvent.TransformReason.SHEARED).isCancelled()) {
+                    return false;
+                }
+                // CraftBukkit end
                 this.world.addEntity(entitycow);
 
                 for (int i = 0; i < 5; ++i) {