PaperMC/paper-server/nms-patches/net/minecraft/world/entity/animal/EntityMushroomCow.patch

--- a/net/minecraft/world/entity/animal/EntityMushroomCow.java
+++ b/net/minecraft/world/entity/animal/EntityMushroomCow.java
@@ -42,6 +42,13 @@
 import net.minecraft.world.level.gameevent.GameEvent;
 import org.apache.commons.lang3.tuple.Pair;
 
+// CraftBukkit start
+import org.bukkit.Bukkit;
+import org.bukkit.craftbukkit.event.CraftEventFactory;
+import org.bukkit.event.entity.EntityDropItemEvent;
+import org.bukkit.event.entity.EntityTransformEvent;
+// CraftBukkit end
+
 public class EntityMushroomCow extends EntityCow implements IShearable {
 
     private static final DataWatcherObject<String> DATA_TYPE = DataWatcher.a(EntityMushroomCow.class, DataWatcherRegistry.STRING);
@@ -113,6 +120,11 @@
             this.playSound(soundeffect, 1.0F, 1.0F);
             return EnumInteractionResult.a(this.level.isClientSide);
         } else if (itemstack.a(Items.SHEARS) && this.canShear()) {
+            // CraftBukkit start
+            if (!CraftEventFactory.handlePlayerShearEntityEvent(entityhuman, this, itemstack, enumhand)) {
+                return EnumInteractionResult.PASS;
+            }
+            // CraftBukkit end
             this.shear(SoundCategory.PLAYERS);
             this.a(GameEvent.SHEAR, (Entity) entityhuman);
             if (!this.level.isClientSide) {
@@ -160,7 +172,7 @@
         this.level.playSound((EntityHuman) null, (Entity) this, SoundEffects.MOOSHROOM_SHEAR, soundcategory, 1.0F, 1.0F);
         if (!this.level.isClientSide()) {
             ((WorldServer) this.level).a(Particles.EXPLOSION, this.locX(), this.e(0.5D), this.locZ(), 1, 0.0D, 0.0D, 0.0D, 0.0D);
-            this.die();
+            // this.die(); // CraftBukkit - moved down
             EntityCow entitycow = (EntityCow) EntityTypes.COW.a(this.level);
 
             entitycow.setPositionRotation(this.locX(), this.locY(), this.locZ(), this.getYRot(), this.getXRot());
@@ -176,10 +188,25 @@
             }
 
             entitycow.setInvulnerable(this.isInvulnerable());
-            this.level.addEntity(entitycow);
+            // CraftBukkit start
+            if (CraftEventFactory.callEntityTransformEvent(this, entitycow, EntityTransformEvent.TransformReason.SHEARED).isCancelled()) {
+                return;
+            }
+            this.level.addEntity(entitycow, org.bukkit.event.entity.CreatureSpawnEvent.SpawnReason.SHEARED);
+
+            this.die(); // CraftBukkit - from above
+            // CraftBukkit end
 
             for (int i = 0; i < 5; ++i) {
-                this.level.addEntity(new EntityItem(this.level, this.locX(), this.e(1.0D), this.locZ(), new ItemStack(this.getVariant().blockState.getBlock())));
+                // CraftBukkit start
+                EntityItem entityitem = new EntityItem(this.level, this.locX(), this.e(1.0D), this.locZ(), new ItemStack(this.getVariant().blockState.getBlock()));
+                EntityDropItemEvent event = new EntityDropItemEvent(this.getBukkitEntity(), (org.bukkit.entity.Item) entityitem.getBukkitEntity());
+                Bukkit.getPluginManager().callEvent(event);
+                if (event.isCancelled()) {
+                    continue;
+                }
+                this.level.addEntity(entityitem);
+                // CraftBukkit end
             }
         }