From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
From: Noah van der Aa <ndvdaa@gmail.com>
Date: Sun, 8 Aug 2021 19:56:02 +0200
Subject: [PATCH] Add CompostItemEvent and EntityCompostItemEvent


diff --git a/src/main/java/net/minecraft/world/level/block/ComposterBlock.java b/src/main/java/net/minecraft/world/level/block/ComposterBlock.java
index e81bda56c58df6c3109382c17e86f4cc0f16cf81..fb4382337fe83f7d00c2212a7a71e0ba5bdd51cc 100644
--- a/src/main/java/net/minecraft/world/level/block/ComposterBlock.java
+++ b/src/main/java/net/minecraft/world/level/block/ComposterBlock.java
@@ -232,6 +232,9 @@ public class ComposterBlock extends Block implements WorldlyContainerHolder {
                 // Paper start - EntityChangeBlockEvent
                 double rand = world.getRandom().nextDouble();
                 BlockState dummyBlockState = ComposterBlock.addItem(player, state, org.bukkit.craftbukkit.util.DummyGeneratorAccess.INSTANCE, pos, itemstack, rand);
+                if (dummyBlockState == null) {
+                    return InteractionResult.PASS;
+                }
                 if (state != dummyBlockState && org.bukkit.craftbukkit.event.CraftEventFactory.callEntityChangeBlockEvent(player, pos, dummyBlockState).isCancelled()) { // if block state will change and event cancelled
                     return InteractionResult.sidedSuccess(world.isClientSide);
                 }
@@ -261,6 +264,11 @@ public class ComposterBlock extends Block implements WorldlyContainerHolder {
             // CraftBukkit start
             double rand = world.getRandom().nextDouble();
             BlockState iblockdata1 = ComposterBlock.addItem(user, state, DummyGeneratorAccess.INSTANCE, pos, stack, rand);
+            // Paper start
+            if (iblockdata1 == null) {
+                return state;
+            }
+            // Paper end
             if (state == iblockdata1 || org.bukkit.craftbukkit.event.CraftEventFactory.callEntityChangeBlockEvent(user, pos, iblockdata1).isCancelled()) {
                 return state;
             }
@@ -315,7 +323,22 @@ public class ComposterBlock extends Block implements WorldlyContainerHolder {
         int i = (Integer) iblockdata.getValue(ComposterBlock.LEVEL);
         float f = ComposterBlock.COMPOSTABLES.getFloat(itemstack.getItem());
 
-        if ((i != 0 || f <= 0.0F) && rand >= (double) f) {
+        // Paper start
+        boolean willRaiseLevel = !((i != 0 || f <= 0.0F) && rand >= (double) f);
+        if (generatoraccess == DummyGeneratorAccess.INSTANCE || entity == null) { // call event on test run or when entity is null (via hopper)
+            final io.papermc.paper.event.block.CompostItemEvent event;
+            if (entity == null) {
+                event = new io.papermc.paper.event.block.CompostItemEvent(org.bukkit.craftbukkit.block.CraftBlock.at(generatoraccess, blockposition), itemstack.getBukkitStack(), willRaiseLevel);
+            } else {
+                event = new io.papermc.paper.event.entity.EntityCompostItemEvent(entity.getBukkitEntity(), org.bukkit.craftbukkit.block.CraftBlock.at(generatoraccess, blockposition), itemstack.getBukkitStack(), willRaiseLevel);
+            }
+            if (!event.callEvent()) {
+                return null;
+            }
+            willRaiseLevel = event.willRaiseLevel();
+        }
+        if (!willRaiseLevel) {
+            // Paper end
             return iblockdata;
         } else {
             int j = i + 1;
@@ -460,6 +483,11 @@ public class ComposterBlock extends Block implements WorldlyContainerHolder {
                 this.changed = true;
                 BlockState iblockdata = ComposterBlock.addItem((Entity) null, this.state, this.level, this.pos, itemstack);
 
+                // Paper start
+                if (iblockdata == null) {
+                    return;
+                }
+                // Paper end
                 this.level.levelEvent(1500, this.pos, iblockdata != this.state ? 1 : 0);
                 this.removeItemNoUpdate(0);
             }