Paper/nms-patches/EntityMushroomCow.patch

--- a/net/minecraft/server/EntityMushroomCow.java
+++ b/net/minecraft/server/EntityMushroomCow.java
@@ -4,6 +4,10 @@
 import java.util.Random;
 import java.util.UUID;
 import org.apache.commons.lang3.tuple.Pair;
+// CraftBukkit start
+import org.bukkit.craftbukkit.event.CraftEventFactory;
+import org.bukkit.event.entity.EntityTransformEvent;
+// CraftBukkit end
 
 public class EntityMushroomCow extends EntityCow implements IShearable {
 
@@ -75,6 +79,11 @@
             this.playSound(soundeffect, 1.0F, 1.0F);
             return EnumInteractionResult.a(this.world.isClientSide);
         } else if (itemstack.getItem() == Items.SHEARS && this.canShear()) {
+            // CraftBukkit start
+            if (!CraftEventFactory.handlePlayerShearEntityEvent(entityhuman, this, itemstack, enumhand)) {
+                return EnumInteractionResult.PASS;
+            }
+            // CraftBukkit end
             this.shear(SoundCategory.PLAYERS);
             if (!this.world.isClientSide) {
                 itemstack.damage(1, entityhuman, (entityhuman1) -> {
@@ -121,7 +130,7 @@
         this.world.playSound((EntityHuman) null, (Entity) this, SoundEffects.ENTITY_MOOSHROOM_SHEAR, soundcategory, 1.0F, 1.0F);
         if (!this.world.s_()) {
             ((WorldServer) this.world).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.world);
 
             entitycow.setPositionRotation(this.locX(), this.locY(), this.locZ(), this.yaw, this.pitch);
@@ -137,7 +146,14 @@
             }
 
             entitycow.setInvulnerable(this.isInvulnerable());
-            this.world.addEntity(entitycow);
+            // CraftBukkit start
+            if (CraftEventFactory.callEntityTransformEvent(this, entitycow, EntityTransformEvent.TransformReason.SHEARED).isCancelled()) {
+                return;
+            }
+            this.world.addEntity(entitycow, org.bukkit.event.entity.CreatureSpawnEvent.SpawnReason.SHEARED);
+
+            this.die(); // CraftBukkit - from above
+            // CraftBukkit end
 
             for (int i = 0; i < 5; ++i) {
                 this.world.addEntity(new EntityItem(this.world, this.locX(), this.e(1.0D), this.locZ(), new ItemStack(this.getVariant().d.getBlock())));