Use entity IDs in EntityDamageBy*EntityEvents, fixed memory leaks related to PvP/PvE/PvM (#418)

src/pocketmine/Server.php

@@ -1087,6 +1087,31 @@ class Server{
 		return true;
 	}
 
+	/**
+	 * Searches all levels for the entity with the specified ID.
+	 * Useful for tracking entities across multiple worlds without needing strong references.
+	 *
+	 * @param int        $entityId
+	 * @param Level|null $expectedLevel Level to look in first for the target
+	 *
+	 * @return Entity|null
+	 */
+	public function findEntity(int $entityId, Level $expectedLevel = null){
+		$levels = $this->levels;
+		if($expectedLevel !== null){
+			array_unshift($levels, $expectedLevel);
+		}
+
+		foreach($levels as $level){
+			assert(!$level->isClosed());
+			if(($entity = $level->getEntity($entityId)) instanceof Entity){
+				return $entity;
+			}
+		}
+
+		return null;
+	}
+
 	/**
 	 * @param string $variable
 	 * @param string $defaultValue

src/pocketmine/entity/Entity.php

@@ -1652,6 +1652,7 @@ abstract class Entity extends Location implements Metadatable{
 			}
 
 			$this->namedtag = null;
+			$this->lastDamageCause = null;
 		}
 	}
 

src/pocketmine/entity/Living.php

@@ -123,13 +123,15 @@ abstract class Living extends Entity implements Damageable{
 				$e = $source->getChild();
 			}
 
-			if($e->isOnFire() > 0){
-				$this->setOnFire(2 * $this->server->getDifficulty());
-			}
+			if($e !== null){
+				if($e->isOnFire() > 0){
+					$this->setOnFire(2 * $this->server->getDifficulty());
+				}
 
-			$deltaX = $this->x - $e->x;
-			$deltaZ = $this->z - $e->z;
-			$this->knockBack($e, $damage, $deltaX, $deltaZ, $source->getKnockBack());
+				$deltaX = $this->x - $e->x;
+				$deltaZ = $this->z - $e->z;
+				$this->knockBack($e, $damage, $deltaX, $deltaZ, $source->getKnockBack());
+			}
 		}
 
 		$pk = new EntityEventPacket();

src/pocketmine/entity/Squid.php

@@ -60,7 +60,9 @@ class Squid extends WaterAnimal implements Ageable{
 		if($source instanceof EntityDamageByEntityEvent){
 			$this->swimSpeed = mt_rand(150, 350) / 2000;
 			$e = $source->getDamager();
-			$this->swimDirection = (new Vector3($this->x - $e->x, $this->y - $e->y, $this->z - $e->z))->normalize();
+			if($e !== null){
+				$this->swimDirection = (new Vector3($this->x - $e->x, $this->y - $e->y, $this->z - $e->z))->normalize();
+			}
 
 			$pk = new EntityEventPacket();
 			$pk->eid = $this->getId();

src/pocketmine/event/entity/EntityDamageByBlockEvent.php

@@ -24,6 +24,9 @@ namespace pocketmine\event\entity;
 use pocketmine\block\Block;
 use pocketmine\entity\Entity;
 
+/**
+ * Called when an entity takes damage from a block.
+ */
 class EntityDamageByBlockEvent extends EntityDamageEvent{
 
 	/** @var Block */

src/pocketmine/event/entity/EntityDamageByChildEntityEvent.php

@@ -23,10 +23,13 @@ namespace pocketmine\event\entity;
 
 use pocketmine\entity\Entity;
 
+/**
+ * Called when an entity takes damage from an entity sourced from another entity, for example being hit by a snowball thrown by a Player.
+ */
 class EntityDamageByChildEntityEvent extends EntityDamageByEntityEvent{
 
-	/** @var Entity */
-	private $childEntity;
+	/** @var int */
+	private $childEntityEid;
 
 
 	/**
@@ -37,15 +40,17 @@ class EntityDamageByChildEntityEvent extends EntityDamageByEntityEvent{
 	 * @param int|int[] $damage
 	 */
 	public function __construct(Entity $damager, Entity $childEntity, Entity $entity, $cause, $damage){
-		$this->childEntity = $childEntity;
+		$this->childEntityEid = $childEntity->getId();
 		parent::__construct($damager, $entity, $cause, $damage);
 	}
 
 	/**
-	 * @return Entity
+	 * Returns the entity which caused the damage, or null if the entity has been killed or closed.
+	 *
+	 * @return Entity|null
 	 */
 	public function getChild(){
-		return $this->childEntity;
+		return $this->getEntity()->getLevel()->getServer()->findEntity($this->childEntityEid, $this->getEntity()->getLevel());
 	}
 
 

src/pocketmine/event/entity/EntityDamageByEntityEvent.php

@@ -24,10 +24,13 @@ namespace pocketmine\event\entity;
 use pocketmine\entity\Effect;
 use pocketmine\entity\Entity;
 
+/**
+ * Called when an entity takes damage from another entity.
+ */
 class EntityDamageByEntityEvent extends EntityDamageEvent{
 
-	/** @var Entity */
-	private $damager;
+	/** @var int */
+	private $damagerEid;
 	/** @var float */
 	private $knockBack;
 
@@ -39,7 +42,7 @@ class EntityDamageByEntityEvent extends EntityDamageEvent{
 	 * @param float     $knockBack
 	 */
 	public function __construct(Entity $damager, Entity $entity, $cause, $damage, $knockBack = 0.4){
-		$this->damager = $damager;
+		$this->damagerEid = $damager->getId();
 		$this->knockBack = $knockBack;
 		parent::__construct($entity, $cause, $damage);
 		$this->addAttackerModifiers($damager);
@@ -56,10 +59,12 @@ class EntityDamageByEntityEvent extends EntityDamageEvent{
 	}
 
 	/**
-	 * @return Entity
+	 * Returns the attacking entity, or null if the attacker has been killed or closed.
+	 *
+	 * @return Entity|null
 	 */
 	public function getDamager(){
-		return $this->damager;
+		return $this->getEntity()->getLevel()->getServer()->findEntity($this->damagerEid, $this->getEntity()->getLevel());
 	}
 
 	/**

src/pocketmine/event/entity/EntityDamageEvent.php

@@ -25,6 +25,9 @@ use pocketmine\entity\Effect;
 use pocketmine\entity\Entity;
 use pocketmine\event\Cancellable;
 
+/**
+ * Called when an entity takes damage.
+ */
 class EntityDamageEvent extends EntityEvent implements Cancellable{
 	public static $handlerList = null;