PaperMC/paper-server/patches/sources/net/minecraft/world/level/ServerExplosion.java.patch

--- a/net/minecraft/world/level/ServerExplosion.java
+++ b/net/minecraft/world/level/ServerExplosion.java
@@ -22,18 +22,27 @@
 import net.minecraft.world.entity.EntityType;
 import net.minecraft.world.entity.LivingEntity;
 import net.minecraft.world.entity.ai.attributes.Attributes;
+import net.minecraft.world.entity.boss.EnderDragonPart;
+import net.minecraft.world.entity.boss.enderdragon.EnderDragon;
 import net.minecraft.world.entity.item.ItemEntity;
 import net.minecraft.world.entity.item.PrimedTnt;
 import net.minecraft.world.entity.player.Player;
 import net.minecraft.world.item.ItemStack;
 import net.minecraft.world.level.block.BaseFireBlock;
 import net.minecraft.world.level.block.Block;
-import net.minecraft.world.level.block.state.BlockState;
 import net.minecraft.world.level.gameevent.GameEvent;
 import net.minecraft.world.level.material.FluidState;
 import net.minecraft.world.phys.AABB;
 import net.minecraft.world.phys.HitResult;
 import net.minecraft.world.phys.Vec3;
+import net.minecraft.world.level.block.Blocks;
+import net.minecraft.world.level.block.state.BlockState;
+import org.bukkit.craftbukkit.event.CraftEventFactory;
+import org.bukkit.craftbukkit.util.CraftLocation;
+import org.bukkit.event.entity.EntityExplodeEvent;
+import org.bukkit.Location;
+import org.bukkit.event.block.BlockExplodeEvent;
+// CraftBukkit end
 
 public class ServerExplosion implements Explosion {
 
@@ -50,16 +59,21 @@
     private final DamageSource damageSource;
     private final ExplosionDamageCalculator damageCalculator;
     private final Map<Player, Vec3> hitPlayers = new HashMap();
+    // CraftBukkit - add field
+    public boolean wasCanceled = false;
+    public float yield;
+    // CraftBukkit end
 
     public ServerExplosion(ServerLevel world, @Nullable Entity entity, @Nullable DamageSource damageSource, @Nullable ExplosionDamageCalculator behavior, Vec3 pos, float power, boolean createFire, Explosion.BlockInteraction destructionType) {
         this.level = world;
         this.source = entity;
-        this.radius = power;
+        this.radius = (float) Math.max(power, 0.0); // CraftBukkit - clamp bad values
         this.center = pos;
         this.fire = createFire;
         this.blockInteraction = destructionType;
         this.damageSource = damageSource == null ? world.damageSources().explosion(this) : damageSource;
         this.damageCalculator = behavior == null ? this.makeDamageCalculator(entity) : behavior;
+        this.yield = this.blockInteraction == Explosion.BlockInteraction.DESTROY_WITH_DECAY ? 1.0F / this.radius : 1.0F; // CraftBukkit
     }
 
     private ExplosionDamageCalculator makeDamageCalculator(@Nullable Entity entity) {
@@ -195,7 +209,35 @@
                         float f2 = !flag && f1 == 0.0F ? 0.0F : ServerExplosion.getSeenPercent(this.center, entity);
 
                         if (flag) {
-                            entity.hurtServer(this.level, this.damageSource, this.damageCalculator.getEntityDamageAmount(this, entity, f2));
+                            // CraftBukkit start
+
+                            // Special case ender dragon only give knockback if no damage is cancelled
+                            // Thinks to note:
+                            // - Setting a velocity to a ComplexEntityPart is ignored (and therefore not needed)
+                            // - Damaging ComplexEntityPart while forward the damage to EntityEnderDragon
+                            // - Damaging EntityEnderDragon does nothing
+                            // - EntityEnderDragon hitbock always covers the other parts and is therefore always present
+                            if (entity instanceof EnderDragonPart) {
+                                continue;
+                            }
+
+                            entity.lastDamageCancelled = false;
+
+                            if (entity instanceof EnderDragon) {
+                                for (EnderDragonPart entityComplexPart : ((EnderDragon) entity).subEntities) {
+                                    // Calculate damage separately for each EntityComplexPart
+                                    if (list.contains(entityComplexPart)) {
+                                        entityComplexPart.hurtServer(this.level, this.damageSource, this.damageCalculator.getEntityDamageAmount(this, entity, f2));
+                                    }
+                                }
+                            } else {
+                                entity.hurtServer(this.level, this.damageSource, this.damageCalculator.getEntityDamageAmount(this, entity, f2));
+                            }
+
+                            if (entity.lastDamageCancelled) { // SPIGOT-5339, SPIGOT-6252, SPIGOT-6777: Skip entity if damage event was cancelled
+                                continue;
+                            }
+                            // CraftBukkit end
                         }
 
                         double d5 = (1.0D - d0) * (double) f2 * (double) f1;
@@ -214,6 +256,17 @@
                         d3 *= d6;
                         Vec3 vec3d = new Vec3(d1, d2, d3);
 
+                        // CraftBukkit start - Call EntityKnockbackEvent
+                        if (entity instanceof LivingEntity) {
+                            Vec3 result = entity.getDeltaMovement().add(vec3d);
+                            org.bukkit.event.entity.EntityKnockbackEvent event = CraftEventFactory.callEntityKnockbackEvent((org.bukkit.craftbukkit.entity.CraftLivingEntity) entity.getBukkitEntity(), this.source, org.bukkit.event.entity.EntityKnockbackEvent.KnockbackCause.EXPLOSION, d6, vec3d, result.x, result.y, result.z);
+
+                            // SPIGOT-7640: Need to subtract entity movement from the event result,
+                            // since the code below (the setDeltaMovement call as well as the hitPlayers map)
+                            // want the vector to be the relative velocity will the event provides the absolute velocity
+                            vec3d = (event.isCancelled()) ? Vec3.ZERO : new Vec3(event.getFinalKnockback().getX(), event.getFinalKnockback().getY(), event.getFinalKnockback().getZ()).subtract(entity.getDeltaMovement());
+                        }
+                        // CraftBukkit end
                         entity.push(vec3d);
                         if (entity instanceof Player) {
                             Player entityhuman = (Player) entity;
@@ -235,10 +288,62 @@
         List<ServerExplosion.StackCollector> list1 = new ArrayList();
 
         Util.shuffle(positions, this.level.random);
+        // CraftBukkit start
+        org.bukkit.World bworld = this.level.getWorld();
+        Location location = CraftLocation.toBukkit(this.center, bworld);
+
+        List<org.bukkit.block.Block> blockList = new ObjectArrayList<>();
+        for (int i1 = positions.size() - 1; i1 >= 0; i1--) {
+            BlockPos cpos = positions.get(i1);
+            org.bukkit.block.Block bblock = bworld.getBlockAt(cpos.getX(), cpos.getY(), cpos.getZ());
+            if (!bblock.getType().isAir()) {
+                blockList.add(bblock);
+            }
+        }
+
+        List<org.bukkit.block.Block> bukkitBlocks;
+
+        if (this.source != null) {
+            EntityExplodeEvent event = CraftEventFactory.callEntityExplodeEvent(this.source, blockList, this.yield, this.getBlockInteraction());
+            this.wasCanceled = event.isCancelled();
+            bukkitBlocks = event.blockList();
+            this.yield = event.getYield();
+        } else {
+            org.bukkit.block.Block block = location.getBlock();
+            org.bukkit.block.BlockState blockState = (this.damageSource.getDirectBlockState() != null) ? this.damageSource.getDirectBlockState() : block.getState();
+            BlockExplodeEvent event = CraftEventFactory.callBlockExplodeEvent(block, blockState, blockList, this.yield, this.getBlockInteraction());
+            this.wasCanceled = event.isCancelled();
+            bukkitBlocks = event.blockList();
+            this.yield = event.getYield();
+        }
+
+        positions.clear();
+
+        for (org.bukkit.block.Block bblock : bukkitBlocks) {
+            BlockPos coords = new BlockPos(bblock.getX(), bblock.getY(), bblock.getZ());
+            positions.add(coords);
+        }
+
+        if (this.wasCanceled) {
+            return;
+        }
+        // CraftBukkit end
         Iterator iterator = positions.iterator();
 
         while (iterator.hasNext()) {
             BlockPos blockposition = (BlockPos) iterator.next();
+            // CraftBukkit start - TNTPrimeEvent
+            BlockState iblockdata = this.level.getBlockState(blockposition);
+            Block block = iblockdata.getBlock();
+            if (block instanceof net.minecraft.world.level.block.TntBlock) {
+                Entity sourceEntity = this.source == null ? null : this.source;
+                BlockPos sourceBlock = sourceEntity == null ? BlockPos.containing(this.center) : null;
+                if (!CraftEventFactory.callTNTPrimeEvent(this.level, blockposition, org.bukkit.event.block.TNTPrimeEvent.PrimeCause.EXPLOSION, sourceEntity, sourceBlock)) {
+                    this.level.sendBlockUpdated(blockposition, Blocks.AIR.defaultBlockState(), iblockdata, 3); // Update the block on the client
+                    continue;
+                }
+            }
+            // CraftBukkit end
 
             this.level.getBlockState(blockposition).onExplosionHit(this.level, blockposition, this, (itemstack, blockposition1) -> {
                 ServerExplosion.addOrAppendStack(list1, itemstack, blockposition1);
@@ -262,13 +367,22 @@
             BlockPos blockposition = (BlockPos) iterator.next();
 
             if (this.level.random.nextInt(3) == 0 && this.level.getBlockState(blockposition).isAir() && this.level.getBlockState(blockposition.below()).isSolidRender()) {
-                this.level.setBlockAndUpdate(blockposition, BaseFireBlock.getState(this.level, blockposition));
+                // CraftBukkit start - Ignition by explosion
+                if (!org.bukkit.craftbukkit.event.CraftEventFactory.callBlockIgniteEvent(this.level, blockposition, this).isCancelled()) {
+                    this.level.setBlockAndUpdate(blockposition, BaseFireBlock.getState(this.level, blockposition));
+                }
+                // CraftBukkit end
             }
         }
 
     }
 
     public void explode() {
+        // CraftBukkit start
+        if (this.radius < 0.1F) {
+            return;
+        }
+        // CraftBukkit end
         this.level.gameEvent(this.source, (Holder) GameEvent.EXPLODE, this.center);
         List<BlockPos> list = this.calculateExplodedPositions();
 
@@ -288,6 +402,7 @@
     }
 
     private static void addOrAppendStack(List<ServerExplosion.StackCollector> droppedItemsOut, ItemStack item, BlockPos pos) {
+        if (item.isEmpty()) return; // CraftBukkit - SPIGOT-5425
         Iterator iterator = droppedItemsOut.iterator();
 
         do {