Fix DamageSource API (#10307)

Uses the correct entity in the EntityDamageByEntity event
Returns the correct entity for API's DamageSource#getCausingEntity

patches/api/Fix-DamageSource-API.patch

@@ -0,0 +1,31 @@
+From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
+From: Jake Potrebic <jake.m.potrebic@gmail.com>
+Date: Sat, 16 Mar 2024 11:21:14 -0700
+Subject: [PATCH] Fix DamageSource API
+
+
+diff --git a/src/main/java/org/bukkit/event/entity/EntityDamageByEntityEvent.java b/src/main/java/org/bukkit/event/entity/EntityDamageByEntityEvent.java
+index 0000000000000000000000000000000000000000..0000000000000000000000000000000000000000 100644
+--- a/src/main/java/org/bukkit/event/entity/EntityDamageByEntityEvent.java
++++ b/src/main/java/org/bukkit/event/entity/EntityDamageByEntityEvent.java
+@@ -0,0 +0,0 @@ public class EntityDamageByEntityEvent extends EntityDamageEvent {
+     }
+     // Paper end
+ 
++    // Paper start
++    /**
++     * {@inheritDoc}
++     * <p>
++     * The {@link DamageSource#getDirectEntity()} may be different from the {@link #getDamager()}
++     * if the Minecraft damage source did not originally include an damager entity, but one was included
++     * for this event {@link #getDamager()}.
++     */
++    @Override
++    public @NotNull DamageSource getDamageSource() {
++        return super.getDamageSource();
++    }
++    // Paper end
++
+     /**
+      * Returns the entity that damaged the defender.
+      *

patches/server/Fix-DamageSource-API.patch

@@ -0,0 +1,198 @@
+From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
+From: Jake Potrebic <jake.m.potrebic@gmail.com>
+Date: Sat, 9 Mar 2024 14:13:04 -0800
+Subject: [PATCH] Fix DamageSource API
+
+Uses the correct entity in the EntityDamageByEntity event
+Returns the correct entity for API's DamageSource#getCausingEntity
+
+diff --git a/src/main/java/net/minecraft/world/damagesource/DamageSource.java b/src/main/java/net/minecraft/world/damagesource/DamageSource.java
+index 0000000000000000000000000000000000000000..0000000000000000000000000000000000000000 100644
+--- a/src/main/java/net/minecraft/world/damagesource/DamageSource.java
++++ b/src/main/java/net/minecraft/world/damagesource/DamageSource.java
+@@ -0,0 +0,0 @@ public class DamageSource {
+     private boolean withSweep = false;
+     private boolean melting = false;
+     private boolean poison = false;
+-    private Entity customCausingEntity = null; // This field is a helper for when causing entity damage is not set by vanilla
++    @Nullable
++    private Entity customEventDamager = null; // This field is a helper for when causing entity damage is not set by vanilla // Paper - fix DamageSource API
+ 
+     public DamageSource sweep() {
+         this.withSweep = true;
+@@ -0,0 +0,0 @@ public class DamageSource {
+         return this.poison;
+     }
+ 
+-    public Entity getCausingEntity() {
+-        return (this.customCausingEntity != null) ? this.customCausingEntity : this.causingEntity;
++    // Paper start - fix DamageSource API
++    public @Nullable Entity getCustomEventDamager() {
++        return (this.customEventDamager != null) ? this.customEventDamager : this.directEntity;
+     }
+ 
+-    public DamageSource customCausingEntity(Entity entity) {
++    public DamageSource customEventDamager(Entity entity) {
++        if (this.directEntity != null) {
++            throw new IllegalStateException("Cannot set a custom event damager entity when a direct entity is already set (report as a bug to Paper)");
++        }
+         DamageSource damageSource = this.cloneInstance();
+-        damageSource.customCausingEntity = entity;
++        damageSource.customEventDamager = entity;
++        // Paper end - fix DamageSource API
+         return damageSource;
+     }
+ 
+diff --git a/src/main/java/net/minecraft/world/entity/Entity.java b/src/main/java/net/minecraft/world/entity/Entity.java
+index 0000000000000000000000000000000000000000..0000000000000000000000000000000000000000 100644
+--- a/src/main/java/net/minecraft/world/entity/Entity.java
++++ b/src/main/java/net/minecraft/world/entity/Entity.java
+@@ -0,0 +0,0 @@ public abstract class Entity implements Nameable, EntityAccess, CommandSource, S
+             return;
+         }
+ 
+-        if (!this.hurt(this.damageSources().lightningBolt().customCausingEntity(lightning), 5.0F)) {
++        if (!this.hurt(this.damageSources().lightningBolt().customEventDamager(lightning), 5.0F)) { // Paper - fix DamageSource API
+             return;
+         }
+         // CraftBukkit end
+diff --git a/src/main/java/net/minecraft/world/entity/animal/Turtle.java b/src/main/java/net/minecraft/world/entity/animal/Turtle.java
+index 0000000000000000000000000000000000000000..0000000000000000000000000000000000000000 100644
+--- a/src/main/java/net/minecraft/world/entity/animal/Turtle.java
++++ b/src/main/java/net/minecraft/world/entity/animal/Turtle.java
+@@ -0,0 +0,0 @@ public class Turtle extends Animal {
+ 
+     @Override
+     public void thunderHit(ServerLevel world, LightningBolt lightning) {
+-        this.hurt(this.damageSources().lightningBolt().customCausingEntity(lightning), Float.MAX_VALUE); // CraftBukkit
++        this.hurt(this.damageSources().lightningBolt().customEventDamager(lightning), Float.MAX_VALUE); // CraftBukkit // Paper - fix DamageSource API
+     }
+ 
+     @Override
+diff --git a/src/main/java/net/minecraft/world/entity/decoration/HangingEntity.java b/src/main/java/net/minecraft/world/entity/decoration/HangingEntity.java
+index 0000000000000000000000000000000000000000..0000000000000000000000000000000000000000 100644
+--- a/src/main/java/net/minecraft/world/entity/decoration/HangingEntity.java
++++ b/src/main/java/net/minecraft/world/entity/decoration/HangingEntity.java
+@@ -0,0 +0,0 @@ public abstract class HangingEntity extends Entity {
+         } else {
+             if (!this.isRemoved() && !this.level().isClientSide) {
+                 // CraftBukkit start - fire break events
+-                Entity damager = (source.isIndirect()) ? source.getEntity() : source.getDirectEntity();
++                Entity damager = (source.isIndirect() && source.getEntity() != null) ? source.getEntity() : source.getDirectEntity(); // Paper - fix DamageSource API
+                 HangingBreakEvent event;
+                 if (damager != null) {
+                     event = new HangingBreakByEntityEvent((Hanging) this.getBukkitEntity(), damager.getBukkitEntity(), source.is(DamageTypeTags.IS_EXPLOSION) ? HangingBreakEvent.RemoveCause.EXPLOSION : HangingBreakEvent.RemoveCause.ENTITY);
+diff --git a/src/main/java/net/minecraft/world/entity/projectile/EvokerFangs.java b/src/main/java/net/minecraft/world/entity/projectile/EvokerFangs.java
+index 0000000000000000000000000000000000000000..0000000000000000000000000000000000000000 100644
+--- a/src/main/java/net/minecraft/world/entity/projectile/EvokerFangs.java
++++ b/src/main/java/net/minecraft/world/entity/projectile/EvokerFangs.java
+@@ -0,0 +0,0 @@ public class EvokerFangs extends Entity implements TraceableEntity {
+ 
+         if (target.isAlive() && !target.isInvulnerable() && target != entityliving1) {
+             if (entityliving1 == null) {
+-                target.hurt(this.damageSources().magic().customCausingEntity(this), 6.0F); // CraftBukkit
++                target.hurt(this.damageSources().magic().customEventDamager(this), 6.0F); // CraftBukkit // Paper - fix DamageSource API
+             } else {
+                 if (entityliving1.isAlliedTo((Entity) target)) {
+                     return;
+diff --git a/src/main/java/net/minecraft/world/entity/projectile/ThrownEnderpearl.java b/src/main/java/net/minecraft/world/entity/projectile/ThrownEnderpearl.java
+index 0000000000000000000000000000000000000000..0000000000000000000000000000000000000000 100644
+--- a/src/main/java/net/minecraft/world/entity/projectile/ThrownEnderpearl.java
++++ b/src/main/java/net/minecraft/world/entity/projectile/ThrownEnderpearl.java
+@@ -0,0 +0,0 @@ public class ThrownEnderpearl extends ThrowableItemProjectile {
+ 
+                         entityplayer.connection.teleport(teleEvent.getTo());
+                         entity.resetFallDistance();
+-                        entity.hurt(this.damageSources().fall().customCausingEntity(this), 5.0F); // CraftBukkit
++                        entity.hurt(this.damageSources().fall().customEventDamager(this), 5.0F); // CraftBukkit // Paper - fix DamageSource API
+                     }
+                     // CraftBukkit end
+                     this.level().playSound((Player) null, this.getX(), this.getY(), this.getZ(), SoundEvents.PLAYER_TELEPORT, SoundSource.PLAYERS);
+diff --git a/src/main/java/net/minecraft/world/entity/projectile/WitherSkull.java b/src/main/java/net/minecraft/world/entity/projectile/WitherSkull.java
+index 0000000000000000000000000000000000000000..0000000000000000000000000000000000000000 100644
+--- a/src/main/java/net/minecraft/world/entity/projectile/WitherSkull.java
++++ b/src/main/java/net/minecraft/world/entity/projectile/WitherSkull.java
+@@ -0,0 +0,0 @@ public class WitherSkull extends AbstractHurtingProjectile {
+                     }
+                 }
+             } else {
+-                flag = entity.hurt(this.damageSources().magic().customCausingEntity(this), 5.0F); // Paper - Fire EntityDamageByEntityEvent for unowned wither skulls
++                flag = entity.hurt(this.damageSources().magic().customEventDamager(this), 5.0F); // Paper - Fire EntityDamageByEntityEvent for unowned wither skulls // Paper - fix DamageSource API
+             }
+ 
+             if (flag && entity instanceof LivingEntity) {
+diff --git a/src/main/java/net/minecraft/world/level/Explosion.java b/src/main/java/net/minecraft/world/level/Explosion.java
+index 0000000000000000000000000000000000000000..0000000000000000000000000000000000000000 100644
+--- a/src/main/java/net/minecraft/world/level/Explosion.java
++++ b/src/main/java/net/minecraft/world/level/Explosion.java
+@@ -0,0 +0,0 @@ public class Explosion {
+         this.z = z;
+         this.fire = createFire;
+         this.blockInteraction = destructionType;
+-        this.damageSource = damageSource == null ? world.damageSources().explosion(this).customCausingEntity(entity) : damageSource.customCausingEntity(entity); // CraftBukkit - handle source entity
++        this.damageSource = damageSource == null ? world.damageSources().explosion(this) : damageSource; // CraftBukkit - handle source entity // Paper - revert to fix DamageSource API
+         this.damageCalculator = behavior == null ? this.makeDamageCalculator(entity) : behavior;
+         this.smallExplosionParticles = particle;
+         this.largeExplosionParticles = emitterParticle;
+diff --git a/src/main/java/org/bukkit/craftbukkit/damage/CraftDamageSource.java b/src/main/java/org/bukkit/craftbukkit/damage/CraftDamageSource.java
+index 0000000000000000000000000000000000000000..0000000000000000000000000000000000000000 100644
+--- a/src/main/java/org/bukkit/craftbukkit/damage/CraftDamageSource.java
++++ b/src/main/java/org/bukkit/craftbukkit/damage/CraftDamageSource.java
+@@ -0,0 +0,0 @@ public class CraftDamageSource implements DamageSource {
+ 
+     @Override
+     public org.bukkit.entity.Entity getCausingEntity() {
+-        net.minecraft.world.entity.Entity entity = this.getHandle().getCausingEntity();
++        net.minecraft.world.entity.Entity entity = this.getHandle().getEntity(); // Paper - fix DamageSource API
+         return (entity != null) ? entity.getBukkitEntity() : null;
+     }
+ 
+@@ -0,0 +0,0 @@ public class CraftDamageSource implements DamageSource {
+ 
+     @Override
+     public boolean isIndirect() {
+-        return this.getHandle().getCausingEntity() != this.getHandle().getDirectEntity();
++        return this.getHandle().isIndirect(); // Paper - fix DamageSource API
+     }
+ 
+     @Override
+diff --git a/src/main/java/org/bukkit/craftbukkit/damage/CraftDamageSourceBuilder.java b/src/main/java/org/bukkit/craftbukkit/damage/CraftDamageSourceBuilder.java
+index 0000000000000000000000000000000000000000..0000000000000000000000000000000000000000 100644
+--- a/src/main/java/org/bukkit/craftbukkit/damage/CraftDamageSourceBuilder.java
++++ b/src/main/java/org/bukkit/craftbukkit/damage/CraftDamageSourceBuilder.java
+@@ -0,0 +0,0 @@ public class CraftDamageSourceBuilder implements DamageSource.Builder {
+ 
+     @Override
+     public DamageSource build() {
++        // Paper start - fix DamageCause API
++        if (this.causingEntity != null && this.directEntity == null) {
++            throw new IllegalArgumentException("Direct entity must be set if causing entity is set");
++        }
++        // Paper end - fix DamageCause API
+         return CraftDamageSource.buildFromBukkit(this.damageType, this.causingEntity, this.directEntity, this.damageLocation);
+     }
+ }
+diff --git a/src/main/java/org/bukkit/craftbukkit/event/CraftEventFactory.java b/src/main/java/org/bukkit/craftbukkit/event/CraftEventFactory.java
+index 0000000000000000000000000000000000000000..0000000000000000000000000000000000000000 100644
+--- a/src/main/java/org/bukkit/craftbukkit/event/CraftEventFactory.java
++++ b/src/main/java/org/bukkit/craftbukkit/event/CraftEventFactory.java
+@@ -0,0 +0,0 @@ public class CraftEventFactory {
+ 
+     private static EntityDamageEvent handleEntityDamageEvent(Entity entity, DamageSource source, Map<DamageModifier, Double> modifiers, Map<DamageModifier, Function<? super Double, Double>> modifierFunctions, boolean cancelled) {
+         CraftDamageSource bukkitDamageSource = new CraftDamageSource(source);
+-        Entity damager = source.getCausingEntity();
++        final Entity damager = source.getCustomEventDamager(); // Paper - fix DamageSource API
+         if (source.is(DamageTypeTags.IS_EXPLOSION)) {
+             if (damager == null) {
+                 return CraftEventFactory.callEntityDamageEvent(source.getDirectBlock(), entity, DamageCause.BLOCK_EXPLOSION, bukkitDamageSource, modifiers, modifierFunctions, cancelled, source.explodedBlockState); // Paper - Include BlockState for damage
+@@ -0,0 +0,0 @@ public class CraftEventFactory {
+         } else if (damager != null || source.getDirectEntity() != null) {
+             DamageCause cause = (source.isSweep()) ? DamageCause.ENTITY_SWEEP_ATTACK : DamageCause.ENTITY_ATTACK;
+ 
+-            if (bukkitDamageSource.isIndirect() && source.getDirectEntity() != null) {
+-                damager = source.getDirectEntity();
+-            }
++            // Paper - fix DamageSource API
+ 
+             if (damager instanceof net.minecraft.world.entity.projectile.Projectile) {
+                 if (damager.getBukkitEntity() instanceof ThrownPotion) {