Paper/patches/server/0921-Add-drops-to-shear-events.patch

From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
From: Jake Potrebic <jake.m.potrebic@gmail.com>
Date: Tue, 18 May 2021 12:32:02 -0700
Subject: [PATCH] Add drops to shear events


diff --git a/src/main/java/net/minecraft/core/dispenser/ShearsDispenseItemBehavior.java b/src/main/java/net/minecraft/core/dispenser/ShearsDispenseItemBehavior.java
index f32f8d5cb22feb885a53d3b56c04ad4219d2bafa..44b79a7c2f8b95a484d1999fa2167ce588f7985b 100644
--- a/src/main/java/net/minecraft/core/dispenser/ShearsDispenseItemBehavior.java
+++ b/src/main/java/net/minecraft/core/dispenser/ShearsDispenseItemBehavior.java
@@ -103,11 +103,14 @@ public class ShearsDispenseItemBehavior extends OptionalDispenseItemBehavior {
             if (entityliving instanceof Shearable ishearable) {
                 if (ishearable.readyForShearing()) {
                     // CraftBukkit start
-                    if (CraftEventFactory.callBlockShearEntityEvent(entityliving, bukkitBlock, craftItem).isCancelled()) {
+                    // Paper start - Add drops to shear events
+                    org.bukkit.event.block.BlockShearEntityEvent event = CraftEventFactory.callBlockShearEntityEvent(entityliving, bukkitBlock, craftItem, ishearable.generateDefaultDrops());
+                    if (event.isCancelled()) {
+                        // Paper end - Add drops to shear events
                         continue;
                     }
                     // CraftBukkit end
-                    ishearable.shear(SoundSource.BLOCKS);
+                    ishearable.shear(SoundSource.BLOCKS, CraftItemStack.asNMSCopy(event.getDrops())); // Paper - Add drops to shear events
                     worldserver.gameEvent((Entity) null, (Holder) GameEvent.SHEAR, blockposition);
                     return true;
                 }
diff --git a/src/main/java/net/minecraft/world/entity/Shearable.java b/src/main/java/net/minecraft/world/entity/Shearable.java
index 5e8cc5cfac8888628c6d513148f41be09ca65a2c..2ee48ac3b665db2b02bcb1a30ec972d43a3725b0 100644
--- a/src/main/java/net/minecraft/world/entity/Shearable.java
+++ b/src/main/java/net/minecraft/world/entity/Shearable.java
@@ -3,7 +3,13 @@ package net.minecraft.world.entity;
 import net.minecraft.sounds.SoundSource;
 
 public interface Shearable {
+    default void shear(SoundSource soundCategory, java.util.List<net.minecraft.world.item.ItemStack> drops) { this.shear(soundCategory); } // Paper - Add drops to shear events
     void shear(SoundSource shearedSoundCategory);
 
     boolean readyForShearing();
+    // Paper start - custom shear drops; ensure all implementing entities override this
+    default java.util.List<net.minecraft.world.item.ItemStack> generateDefaultDrops() {
+        return java.util.Collections.emptyList();
+    }
+    // Paper end - custom shear drops
 }
diff --git a/src/main/java/net/minecraft/world/entity/animal/MushroomCow.java b/src/main/java/net/minecraft/world/entity/animal/MushroomCow.java
index aa125e3043b120935aaa015803f065f99eb8d050..0c21959f57ae88fcd0a4d6dc911c1ce347c96528 100644
--- a/src/main/java/net/minecraft/world/entity/animal/MushroomCow.java
+++ b/src/main/java/net/minecraft/world/entity/animal/MushroomCow.java
@@ -123,11 +123,18 @@ public class MushroomCow extends Cow implements Shearable, VariantHolder<Mushroo
             return InteractionResult.sidedSuccess(this.level().isClientSide);
         } else if (itemstack.is(Items.SHEARS) && this.readyForShearing()) {
             // CraftBukkit start
-            if (!CraftEventFactory.handlePlayerShearEntityEvent(player, this, itemstack, hand)) {
-                return InteractionResult.PASS;
+            // Paper start - custom shear drops
+            java.util.List<ItemStack> drops = this.generateDefaultDrops();
+            org.bukkit.event.player.PlayerShearEntityEvent event = CraftEventFactory.handlePlayerShearEntityEvent(player, this, itemstack, hand, drops);
+            if (event != null) {
+                if (event.isCancelled()) {
+                    return InteractionResult.PASS;
+                }
+                drops = org.bukkit.craftbukkit.inventory.CraftItemStack.asNMSCopy(event.getDrops());
             }
+            // Paper end - custom shear drops
             // CraftBukkit end
-            this.shear(SoundSource.PLAYERS);
+            this.shear(SoundSource.PLAYERS, drops); // Paper - custom shear drops
             this.gameEvent(GameEvent.SHEAR, player);
             if (!this.level().isClientSide) {
                 itemstack.hurtAndBreak(1, player, getSlotForHand(hand));
@@ -164,6 +171,22 @@ public class MushroomCow extends Cow implements Shearable, VariantHolder<Mushroo
 
     @Override
     public void shear(SoundSource shearedSoundCategory) {
+        // Paper start - custom shear drops
+        this.shear(shearedSoundCategory, this.generateDefaultDrops());
+    }
+
+    @Override
+    public java.util.List<ItemStack> generateDefaultDrops() {
+        java.util.List<ItemStack> dropEntities = new java.util.ArrayList<>(5);
+        for (int i = 0; i < 5; ++i) {
+            dropEntities.add(new ItemStack(this.getVariant().getBlockState().getBlock()));
+        }
+        return dropEntities;
+    }
+
+    @Override
+    public void shear(SoundSource shearedSoundCategory, java.util.List<ItemStack> drops) { // If drops is null, need to generate drops
+        // Paper end - custom shear drops
         this.level().playSound((Player) null, (Entity) this, SoundEvents.MOOSHROOM_SHEAR, shearedSoundCategory, 1.0F, 1.0F);
         if (!this.level().isClientSide()) {
             Cow entitycow = (Cow) EntityType.COW.create(this.level());
@@ -193,17 +216,12 @@ public class MushroomCow extends Cow implements Shearable, VariantHolder<Mushroo
                 this.discard(EntityRemoveEvent.Cause.TRANSFORMATION); // CraftBukkit - from above and add Bukkit remove cause
                 // CraftBukkit end
 
-                for (int i = 0; i < 5; ++i) {
-                    // CraftBukkit start
-                    ItemEntity entityitem = new ItemEntity(this.level(), this.getX(), this.getY(1.0D), this.getZ(), 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().addFreshEntity(entityitem);
-                    // CraftBukkit end
+                // Paper start - custom shear drops; moved drop generation to separate method
+                for (final ItemStack drop : drops) {
+                    ItemEntity entityitem = new ItemEntity(this.level(), this.getX(), this.getY(1.0D), this.getZ(), drop);
+                    this.spawnAtLocation(entityitem);
                 }
+                // Paper end - custom shear drops
             }
         }
 
diff --git a/src/main/java/net/minecraft/world/entity/animal/Sheep.java b/src/main/java/net/minecraft/world/entity/animal/Sheep.java
index 6b26af41423110bd982eb8c0eea0cba5e9fdc633..38ac2759894660be1ee7ba59b0bd1270158e9232 100644
--- a/src/main/java/net/minecraft/world/entity/animal/Sheep.java
+++ b/src/main/java/net/minecraft/world/entity/animal/Sheep.java
@@ -256,11 +256,18 @@ public class Sheep extends Animal implements Shearable {
         if (itemstack.is(Items.SHEARS)) {
             if (!this.level().isClientSide && this.readyForShearing()) {
                 // CraftBukkit start
-                if (!CraftEventFactory.handlePlayerShearEntityEvent(player, this, itemstack, hand)) {
-                    return InteractionResult.PASS;
+                // Paper start - custom shear drops
+                java.util.List<ItemStack> drops = this.generateDefaultDrops();
+                org.bukkit.event.player.PlayerShearEntityEvent event = CraftEventFactory.handlePlayerShearEntityEvent(player, this, itemstack, hand, drops);
+                if (event != null) {
+                    if (event.isCancelled()) {
+                        return InteractionResult.PASS;
+                    }
+                    drops = org.bukkit.craftbukkit.inventory.CraftItemStack.asNMSCopy(event.getDrops());
                 }
+                // Paper end - custom shear drops
                 // CraftBukkit end
-                this.shear(SoundSource.PLAYERS);
+                this.shear(SoundSource.PLAYERS, drops); // Paper
                 this.gameEvent(GameEvent.SHEAR, player);
                 itemstack.hurtAndBreak(1, player, getSlotForHand(hand));
                 return InteractionResult.SUCCESS;
@@ -274,13 +281,30 @@ public class Sheep extends Animal implements Shearable {
 
     @Override
     public void shear(SoundSource shearedSoundCategory) {
+        // Paper start - custom shear drops
+        this.shear(shearedSoundCategory, this.generateDefaultDrops());
+    }
+
+    @Override
+    public java.util.List<ItemStack> generateDefaultDrops() {
+        int count = 1 + this.random.nextInt(3);
+        java.util.List<ItemStack> dropEntities = new java.util.ArrayList<>(count);
+        for (int j = 0; j < count; ++j) {
+            dropEntities.add(new ItemStack(Sheep.ITEM_BY_DYE.get(this.getColor())));
+        }
+        return dropEntities;
+    }
+
+    @Override
+    public void shear(SoundSource shearedSoundCategory, java.util.List<ItemStack> drops) {
+        // Paper end - custom shear drops
         this.level().playSound((Player) null, (Entity) this, SoundEvents.SHEEP_SHEAR, shearedSoundCategory, 1.0F, 1.0F);
         this.setSheared(true);
         int i = 1 + this.random.nextInt(3);
 
-        for (int j = 0; j < i; ++j) {
+        for (final ItemStack drop : drops) { // Paper - custom shear drops (moved drop generation to separate method)
             this.forceDrops = true; // CraftBukkit
-            ItemEntity entityitem = this.spawnAtLocation((ItemLike) Sheep.ITEM_BY_DYE.get(this.getColor()), 1);
+            ItemEntity entityitem = this.spawnAtLocation(drop, 1); // Paper - custom shear drops
             this.forceDrops = false; // CraftBukkit
 
             if (entityitem != null) {
diff --git a/src/main/java/net/minecraft/world/entity/animal/SnowGolem.java b/src/main/java/net/minecraft/world/entity/animal/SnowGolem.java
index 2de1a2f666da9db1832907e1651dbff948e37252..5c2ed3c39c8eb850f3be1e2ea5b5a7ea266e16d1 100644
--- a/src/main/java/net/minecraft/world/entity/animal/SnowGolem.java
+++ b/src/main/java/net/minecraft/world/entity/animal/SnowGolem.java
@@ -146,11 +146,18 @@ public class SnowGolem extends AbstractGolem implements Shearable, RangedAttackM
 
         if (itemstack.is(Items.SHEARS) && this.readyForShearing()) {
             // CraftBukkit start
-            if (!CraftEventFactory.handlePlayerShearEntityEvent(player, this, itemstack, hand)) {
-                return InteractionResult.PASS;
+            // Paper start - custom shear drops
+            java.util.List<ItemStack> drops = this.generateDefaultDrops();
+            org.bukkit.event.player.PlayerShearEntityEvent event = CraftEventFactory.handlePlayerShearEntityEvent(player, this, itemstack, hand, drops);
+            if (event != null) {
+                if (event.isCancelled()) {
+                    return InteractionResult.PASS;
+                }
+                drops = org.bukkit.craftbukkit.inventory.CraftItemStack.asNMSCopy(event.getDrops());
             }
+            // Paper end - custom shear drops
             // CraftBukkit end
-            this.shear(SoundSource.PLAYERS);
+            this.shear(SoundSource.PLAYERS, drops); // Paper
             this.gameEvent(GameEvent.SHEAR, player);
             if (!this.level().isClientSide) {
                 itemstack.hurtAndBreak(1, player, getSlotForHand(hand));
@@ -164,12 +171,28 @@ public class SnowGolem extends AbstractGolem implements Shearable, RangedAttackM
 
     @Override
     public void shear(SoundSource shearedSoundCategory) {
+        // Paper start - custom shear drops
+        this.shear(shearedSoundCategory, this.generateDefaultDrops());
+    }
+
+    @Override
+    public java.util.List<ItemStack> generateDefaultDrops() {
+        return java.util.Collections.singletonList(new ItemStack(Items.CARVED_PUMPKIN));
+    }
+
+    @Override
+    public void shear(SoundSource shearedSoundCategory, java.util.List<ItemStack> drops) {
+        // Paper end - custom shear drops
         this.level().playSound((Player) null, (Entity) this, SoundEvents.SNOW_GOLEM_SHEAR, shearedSoundCategory, 1.0F, 1.0F);
         if (!this.level().isClientSide()) {
             this.setPumpkin(false);
-            this.forceDrops = true; // CraftBukkit
-            this.spawnAtLocation(new ItemStack(Items.CARVED_PUMPKIN), this.getEyeHeight());
-            this.forceDrops = false; // CraftBukkit
+            // Paper start - custom shear drops (moved drop generation to separate method)
+            for (final ItemStack drop : drops) {
+                this.forceDrops = true;
+                this.spawnAtLocation(drop, this.getEyeHeight());
+                this.forceDrops = false;
+            }
+            // Paper end - custom shear drops
         }
 
     }
diff --git a/src/main/java/net/minecraft/world/entity/monster/Bogged.java b/src/main/java/net/minecraft/world/entity/monster/Bogged.java
index dc6230458e09f7555eee7f6a567ff60ad454666b..9d50b9ac8084f3db1844cc7ad1ce9153614ff9d9 100644
--- a/src/main/java/net/minecraft/world/entity/monster/Bogged.java
+++ b/src/main/java/net/minecraft/world/entity/monster/Bogged.java
@@ -80,12 +80,19 @@ public class Bogged extends AbstractSkeleton implements Shearable {
 
         if (itemstack.is(Items.SHEARS) && this.readyForShearing()) {
             // CraftBukkit start
-            if (!org.bukkit.craftbukkit.event.CraftEventFactory.handlePlayerShearEntityEvent(player, this, itemstack, hand)) {
-                this.getEntityData().markDirty(Bogged.DATA_SHEARED); // CraftBukkit - mark dirty to restore sheared state to clients
-                return InteractionResult.PASS;
+            // Paper start - expose drops in event
+            java.util.List<net.minecraft.world.item.ItemStack> drops = generateDefaultDrops();
+            final org.bukkit.event.player.PlayerShearEntityEvent event = org.bukkit.craftbukkit.event.CraftEventFactory.handlePlayerShearEntityEvent(player, this, itemstack, hand, drops);
+            if (event != null) {
+                if (event.isCancelled()) {
+                    if (player instanceof final net.minecraft.server.level.ServerPlayer serverPlayer) this.resendPossiblyDesyncedDataValues(java.util.List.of(Bogged.DATA_SHEARED), serverPlayer);
+                    return InteractionResult.PASS;
+                }
+                drops = org.bukkit.craftbukkit.inventory.CraftItemStack.asNMSCopy(event.getDrops());
+            // Paper end - expose drops in event
             }
             // CraftBukkit end
-            this.shear(SoundSource.PLAYERS);
+            this.shear(SoundSource.PLAYERS, drops); // Paper - expose drops in event
             this.gameEvent(GameEvent.SHEAR, player);
             if (!this.level().isClientSide) {
                 itemstack.hurtAndBreak(1, player, getSlotForHand(hand));
@@ -140,12 +147,31 @@ public class Bogged extends AbstractSkeleton implements Shearable {
 
     @Override
     public void shear(SoundSource shearedSoundCategory) {
+    // Paper start - shear drop API
+        this.shear(shearedSoundCategory, generateDefaultDrops());
+    }
+
+    @Override
+    public void shear(SoundSource shearedSoundCategory, java.util.List<net.minecraft.world.item.ItemStack> drops) {
+    // Paper end - shear drop API
         this.level().playSound((Player) null, (Entity) this, SoundEvents.BOGGED_SHEAR, shearedSoundCategory, 1.0F, 1.0F);
-        this.spawnShearedMushrooms();
+        this.spawnDrops(drops); // Paper - shear drop API
         this.setSheared(true);
     }
 
     private void spawnShearedMushrooms() {
+    // Paper start - shear drops API
+        this.spawnDrops(generateDefaultDrops()); // Only here for people calling spawnSheardMushrooms. Not used otherwise.
+    }
+    private void spawnDrops(java.util.List<net.minecraft.world.item.ItemStack> drops) {
+        drops.forEach(stack -> {
+            this.forceDrops = true;
+            this.spawnAtLocation(stack, this.getBbHeight());
+            this.forceDrops = false;
+        });
+    }
+    private void generateShearedMushrooms(java.util.function.Consumer<ItemStack> stackConsumer) {
+    // Paper end - shear drops API
         Level world = this.level();
 
         if (world instanceof ServerLevel worldserver) {
@@ -156,12 +182,21 @@ public class Bogged extends AbstractSkeleton implements Shearable {
             while (objectlistiterator.hasNext()) {
                 ItemStack itemstack = (ItemStack) objectlistiterator.next();
 
-                this.spawnAtLocation(itemstack, this.getBbHeight());
+                stackConsumer.accept(itemstack); // Paper
             }
         }
 
     }
 
+    // Paper start - shear drops API
+    @Override
+    public java.util.List<ItemStack> generateDefaultDrops() {
+        final java.util.List<ItemStack> drops = new java.util.ArrayList<>();
+        this.generateShearedMushrooms(drops::add);
+        return drops;
+    }
+    // Paper end - shear drops API
+
     @Override
     public boolean readyForShearing() {
         return !this.isSheared() && this.isAlive();
diff --git a/src/main/java/org/bukkit/craftbukkit/event/CraftEventFactory.java b/src/main/java/org/bukkit/craftbukkit/event/CraftEventFactory.java
index 5ba2fb40e4db033a069b7368b481ac81be109e94..5af27ba31f293ba6bcac37047b760db1c3bd8c5f 100644
--- a/src/main/java/org/bukkit/craftbukkit/event/CraftEventFactory.java
+++ b/src/main/java/org/bukkit/craftbukkit/event/CraftEventFactory.java
@@ -1689,20 +1689,20 @@ public class CraftEventFactory {
         player.level().getCraftServer().getPluginManager().callEvent(event);
     }
 
-    public static BlockShearEntityEvent callBlockShearEntityEvent(Entity animal, org.bukkit.block.Block dispenser, CraftItemStack is) {
-        BlockShearEntityEvent bse = new BlockShearEntityEvent(dispenser, animal.getBukkitEntity(), is);
+    public static BlockShearEntityEvent callBlockShearEntityEvent(Entity animal, org.bukkit.block.Block dispenser, CraftItemStack is, List<ItemStack> drops) { // Paper - custom shear drops
+        BlockShearEntityEvent bse = new BlockShearEntityEvent(dispenser, animal.getBukkitEntity(), is, Lists.transform(drops, CraftItemStack::asCraftMirror)); // Paper - custom shear drops
         Bukkit.getPluginManager().callEvent(bse);
         return bse;
     }
 
-    public static boolean handlePlayerShearEntityEvent(net.minecraft.world.entity.player.Player player, Entity sheared, ItemStack shears, InteractionHand hand) {
+    public static PlayerShearEntityEvent handlePlayerShearEntityEvent(net.minecraft.world.entity.player.Player player, Entity sheared, ItemStack shears, InteractionHand hand, List<ItemStack> drops) { // Paper - custom shear drops
         if (!(player instanceof ServerPlayer)) {
-            return true;
+            return null; // Paper - custom shear drops
         }
 
-        PlayerShearEntityEvent event = new PlayerShearEntityEvent((Player) player.getBukkitEntity(), sheared.getBukkitEntity(), CraftItemStack.asCraftMirror(shears), (hand == InteractionHand.OFF_HAND ? EquipmentSlot.OFF_HAND : EquipmentSlot.HAND));
+        PlayerShearEntityEvent event = new PlayerShearEntityEvent((Player) player.getBukkitEntity(), sheared.getBukkitEntity(), CraftItemStack.asCraftMirror(shears), (hand == InteractionHand.OFF_HAND ? EquipmentSlot.OFF_HAND : EquipmentSlot.HAND), Lists.transform(drops, CraftItemStack::asCraftMirror)); // Paper - custom shear drops
         Bukkit.getPluginManager().callEvent(event);
-        return !event.isCancelled();
+        return event; // Paper - custom shear drops
     }
 
     public static Cancellable handleStatisticsIncrease(net.minecraft.world.entity.player.Player entityHuman, net.minecraft.stats.Stat<?> statistic, int current, int newValue) {
diff --git a/src/main/java/org/bukkit/craftbukkit/inventory/CraftItemStack.java b/src/main/java/org/bukkit/craftbukkit/inventory/CraftItemStack.java
index f33742ee06e8443a5f5adaaa987d7523dc193b5a..a1a32a77bda0560a7b7f30a5d1c1837ee96997d3 100644
--- a/src/main/java/org/bukkit/craftbukkit/inventory/CraftItemStack.java
+++ b/src/main/java/org/bukkit/craftbukkit/inventory/CraftItemStack.java
@@ -69,6 +69,16 @@ public final class CraftItemStack extends ItemStack {
         return stack;
     }
 
+    // Paper start
+    public static java.util.List<net.minecraft.world.item.ItemStack> asNMSCopy(java.util.List<? extends ItemStack> originals) {
+        final java.util.List<net.minecraft.world.item.ItemStack> items = new java.util.ArrayList<>(originals.size());
+        for (final ItemStack original : originals) {
+            items.add(asNMSCopy(original));
+        }
+        return items;
+    }
+    // Paper end
+
     public static net.minecraft.world.item.ItemStack copyNMSStack(net.minecraft.world.item.ItemStack original, int amount) {
         net.minecraft.world.item.ItemStack stack = original.copy();
         stack.setCount(amount);
diff --git a/src/test/java/io/papermc/paper/entity/ShearableDropsTest.java b/src/test/java/io/papermc/paper/entity/ShearableDropsTest.java
new file mode 100644
index 0000000000000000000000000000000000000000..e612515f7709dbe5d1fa5751337cdc34fce10a98
--- /dev/null
+++ b/src/test/java/io/papermc/paper/entity/ShearableDropsTest.java
@@ -0,0 +1,34 @@
+package io.papermc.paper.entity;
+
+import io.github.classgraph.ClassGraph;
+import io.github.classgraph.ClassInfo;
+import io.github.classgraph.MethodInfoList;
+import io.github.classgraph.ScanResult;
+import java.util.ArrayList;
+import net.minecraft.world.entity.Shearable;
+import org.bukkit.support.AbstractTestingBase;
+import org.junit.jupiter.params.ParameterizedTest;
+import org.junit.jupiter.params.provider.MethodSource;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+class ShearableDropsTest extends AbstractTestingBase {
+
+    static Iterable<ClassInfo> parameters() {
+        try (ScanResult scanResult = new ClassGraph()
+            .enableClassInfo()
+            .enableMethodInfo()
+            .whitelistPackages("net.minecraft")
+            .scan()
+        ) {
+            return new ArrayList<>(scanResult.getClassesImplementing(Shearable.class.getName()));
+        }
+    }
+
+    @ParameterizedTest
+    @MethodSource("parameters")
+    void checkShearableDropOverrides(final ClassInfo classInfo) {
+        final MethodInfoList generateDefaultDrops = classInfo.getDeclaredMethodInfo("generateDefaultDrops");
+        assertEquals(1, generateDefaultDrops.size(), classInfo.getName() + " doesn't implement Shearable#generateDefaultDrops");
+    }
+}