Paper/paper-server/nms-patches/net/minecraft/world/level/block/BlockComposter.patch

--- a/net/minecraft/world/level/block/BlockComposter.java
+++ b/net/minecraft/world/level/block/BlockComposter.java
@@ -37,6 +37,12 @@
 import net.minecraft.world.phys.shapes.VoxelShapeCollision;
 import net.minecraft.world.phys.shapes.VoxelShapes;
 
+// CraftBukkit start
+import net.minecraft.world.entity.Entity;
+import org.bukkit.craftbukkit.inventory.CraftBlockInventoryHolder;
+import org.bukkit.craftbukkit.util.DummyGeneratorAccess;
+// CraftBukkit end
+
 public class BlockComposter extends Block implements IInventoryHolder {
 
     public static final int READY = 8;
@@ -227,18 +233,25 @@
 
             return EnumInteractionResult.sidedSuccess(world.isClientSide);
         } else if (i == 8) {
-            extractProduce(iblockdata, world, blockposition);
+            extractProduce(iblockdata, world, blockposition, (Entity) null); // CraftBukkit - no event for players
             return EnumInteractionResult.sidedSuccess(world.isClientSide);
         } else {
             return EnumInteractionResult.PASS;
         }
     }
 
-    public static IBlockData insertItem(IBlockData iblockdata, WorldServer worldserver, ItemStack itemstack, BlockPosition blockposition) {
+    public static IBlockData insertItem(IBlockData iblockdata, WorldServer worldserver, ItemStack itemstack, BlockPosition blockposition, Entity entity) { // CraftBukkit
         int i = (Integer) iblockdata.getValue(BlockComposter.LEVEL);
 
         if (i < 7 && BlockComposter.COMPOSTABLES.containsKey(itemstack.getItem())) {
-            IBlockData iblockdata1 = addItem(iblockdata, worldserver, blockposition, itemstack);
+            // CraftBukkit start
+            double rand = worldserver.getRandom().nextDouble();
+            IBlockData iblockdata1 = addItem(iblockdata, DummyGeneratorAccess.INSTANCE, blockposition, itemstack, rand);
+            if (iblockdata == iblockdata1 || org.bukkit.craftbukkit.event.CraftEventFactory.callEntityChangeBlockEvent(entity, blockposition, iblockdata1).isCancelled()) {
+                return iblockdata;
+            }
+            iblockdata1 = addItem(iblockdata, (GeneratorAccess) worldserver, blockposition, itemstack, rand);
+            // CraftBukkit end
 
             itemstack.shrink(1);
             return iblockdata1;
@@ -247,7 +260,15 @@
         }
     }
 
-    public static IBlockData extractProduce(IBlockData iblockdata, World world, BlockPosition blockposition) {
+    // CraftBukkit start
+    public static IBlockData extractProduce(IBlockData iblockdata, World world, BlockPosition blockposition, Entity entity) {
+        if (entity != null) {
+            IBlockData iblockdata1 = empty(iblockdata, DummyGeneratorAccess.INSTANCE, blockposition);
+            if (org.bukkit.craftbukkit.event.CraftEventFactory.callEntityChangeBlockEvent(entity, blockposition, iblockdata1).isCancelled()) {
+                return iblockdata;
+            }
+        }
+        // CraftBukkit end
         if (!world.isClientSide) {
             float f = 0.7F;
             double d0 = (double) (world.random.nextFloat() * 0.7F) + 0.15000000596046448D;
@@ -273,10 +294,16 @@
     }
 
     static IBlockData addItem(IBlockData iblockdata, GeneratorAccess generatoraccess, BlockPosition blockposition, ItemStack itemstack) {
+        // CraftBukkit start
+        return addItem(iblockdata, generatoraccess, blockposition, itemstack, generatoraccess.getRandom().nextDouble());
+    }
+
+    static IBlockData addItem(IBlockData iblockdata, GeneratorAccess generatoraccess, BlockPosition blockposition, ItemStack itemstack, double rand) {
+        // CraftBukkit end
         int i = (Integer) iblockdata.getValue(BlockComposter.LEVEL);
         float f = BlockComposter.COMPOSTABLES.getFloat(itemstack.getItem());
 
-        if ((i != 0 || f <= 0.0F) && generatoraccess.getRandom().nextDouble() >= (double) f) {
+        if ((i != 0 || f <= 0.0F) && rand >= (double) f) {
             return iblockdata;
         } else {
             int j = i + 1;
@@ -324,7 +351,8 @@
     public IWorldInventory getContainer(IBlockData iblockdata, GeneratorAccess generatoraccess, BlockPosition blockposition) {
         int i = (Integer) iblockdata.getValue(BlockComposter.LEVEL);
 
-        return (IWorldInventory) (i == 8 ? new BlockComposter.ContainerOutput(iblockdata, generatoraccess, blockposition, new ItemStack(Items.BONE_MEAL)) : (i < 7 ? new BlockComposter.ContainerInput(iblockdata, generatoraccess, blockposition) : new BlockComposter.ContainerEmpty()));
+        // CraftBukkit - empty generatoraccess, blockposition
+        return (IWorldInventory) (i == 8 ? new BlockComposter.ContainerOutput(iblockdata, generatoraccess, blockposition, new ItemStack(Items.BONE_MEAL)) : (i < 7 ? new BlockComposter.ContainerInput(iblockdata, generatoraccess, blockposition) : new BlockComposter.ContainerEmpty(generatoraccess, blockposition)));
     }
 
     public static class ContainerOutput extends InventorySubcontainer implements IWorldInventory {
@@ -339,6 +367,7 @@
             this.state = iblockdata;
             this.level = generatoraccess;
             this.pos = blockposition;
+            this.bukkitOwner = new CraftBlockInventoryHolder(generatoraccess, blockposition, this); // CraftBukkit
         }
 
         @Override
@@ -363,8 +392,15 @@
 
         @Override
         public void setChanged() {
-            BlockComposter.empty(this.state, this.level, this.pos);
-            this.changed = true;
+            // CraftBukkit start - allow putting items back (eg cancelled InventoryMoveItemEvent)
+            if (this.isEmpty()) {
+                BlockComposter.empty(this.state, this.level, this.pos);
+                this.changed = true;
+            } else {
+                this.level.setBlock(this.pos, this.state, 3);
+                this.changed = false;
+            }
+            // CraftBukkit end
         }
     }
 
@@ -377,6 +413,7 @@
 
         public ContainerInput(IBlockData iblockdata, GeneratorAccess generatoraccess, BlockPosition blockposition) {
             super(1);
+            this.bukkitOwner = new CraftBlockInventoryHolder(generatoraccess, blockposition, this); // CraftBukkit
             this.state = iblockdata;
             this.level = generatoraccess;
             this.pos = blockposition;
@@ -419,8 +456,9 @@
 
     public static class ContainerEmpty extends InventorySubcontainer implements IWorldInventory {
 
-        public ContainerEmpty() {
+        public ContainerEmpty(GeneratorAccess generatoraccess, BlockPosition blockposition) { // CraftBukkit
             super(0);
+            this.bukkitOwner = new CraftBlockInventoryHolder(generatoraccess, blockposition, this); // CraftBukkit
         }
 
         @Override