Revamp Entity construction

This is a similar refactor to the one I recently did for tiles.

- Entity::createEntity() is removed. In its place are Entity::create() (runtime creation, use where you'd use a constructor, accepts a ::class parameter, throws exceptions on unknown entities) and Entity::createFromData() (internal, used to restore entities from chunks, swallows unknown entities and returns null).
- Entity::registerEntity() is renamed to Entity::register().
- Added Entity::override() to allow overriding factory classes without touching save IDs. This allows more cleanly extending & overriding entities. This method only allows overriding registered Entity classes with children of that class, which makes code using the factory much more sane and allows to provide safety guarantees which make the code less nasty.
- Entity::getKnownEntityTypes() is renamed to Entity::getKnownTypes().
- ProjectileItem::getProjectileEntityType() now returns a ::class constant instead of a stringy ID.
- Cleaned up a bunch of nasty code, particularly in Bow.

src/pocketmine/item/Bow.php

@@ -65,61 +65,56 @@ class Bow extends Tool{
 		$p = $diff / 20;
 		$force = min((($p ** 2) + $p * 2) / 3, 1) * 2;
 
+		/** @var ArrowEntity $entity */
+		$entity = Entity::create(ArrowEntity::class, $player->getLevel(), $nbt, $player, $force == 2);
 
-		$entity = Entity::createEntity("Arrow", $player->getLevel(), $nbt, $player, $force == 2);
-		if($entity instanceof Projectile){
-			$infinity = $this->hasEnchantment(Enchantment::INFINITY);
-			if($entity instanceof ArrowEntity){
-				if($infinity){
-					$entity->setPickupMode(ArrowEntity::PICKUP_CREATIVE);
-				}
-				if(($punchLevel = $this->getEnchantmentLevel(Enchantment::PUNCH)) > 0){
-					$entity->setPunchKnockback($punchLevel);
-				}
-			}
-			if(($powerLevel = $this->getEnchantmentLevel(Enchantment::POWER)) > 0){
-				$entity->setBaseDamage($entity->getBaseDamage() + (($powerLevel + 1) / 2));
-			}
-			if($this->hasEnchantment(Enchantment::FLAME)){
-				$entity->setOnFire(intdiv($entity->getFireTicks(), 20) + 100);
-			}
-			$ev = new EntityShootBowEvent($player, $this, $entity, $force);
+		$infinity = $this->hasEnchantment(Enchantment::INFINITY);
+		if($infinity){
+			$entity->setPickupMode(ArrowEntity::PICKUP_CREATIVE);
+		}
+		if(($punchLevel = $this->getEnchantmentLevel(Enchantment::PUNCH)) > 0){
+			$entity->setPunchKnockback($punchLevel);
+		}
+		if(($powerLevel = $this->getEnchantmentLevel(Enchantment::POWER)) > 0){
+			$entity->setBaseDamage($entity->getBaseDamage() + (($powerLevel + 1) / 2));
+		}
+		if($this->hasEnchantment(Enchantment::FLAME)){
+			$entity->setOnFire(intdiv($entity->getFireTicks(), 20) + 100);
+		}
+		$ev = new EntityShootBowEvent($player, $this, $entity, $force);
 
-			if($force < 0.1 or $diff < 5){
-				$ev->setCancelled();
-			}
+		if($force < 0.1 or $diff < 5){
+			$ev->setCancelled();
+		}
 
-			$ev->call();
+		$ev->call();
 
-			$entity = $ev->getProjectile(); //This might have been changed by plugins
+		$entity = $ev->getProjectile(); //This might have been changed by plugins
 
-			if($ev->isCancelled()){
-				$entity->flagForDespawn();
-				$player->getInventory()->sendContents($player);
-			}else{
-				$entity->setMotion($entity->getMotion()->multiply($ev->getForce()));
-				if($player->isSurvival()){
-					if(!$infinity){ //TODO: tipped arrows are still consumed when Infinity is applied
-						$player->getInventory()->removeItem(ItemFactory::get(Item::ARROW, 0, 1));
-					}
-					$this->applyDamage(1);
-				}
-
-				if($entity instanceof Projectile){
-					$projectileEv = new ProjectileLaunchEvent($entity);
-					$projectileEv->call();
-					if($projectileEv->isCancelled()){
-						$ev->getProjectile()->flagForDespawn();
-					}else{
-						$ev->getProjectile()->spawnToAll();
-						$player->getLevel()->broadcastLevelSoundEvent($player, LevelSoundEventPacket::SOUND_BOW);
-					}
-				}else{
-					$entity->spawnToAll();
-				}
-			}
+		if($ev->isCancelled()){
+			$entity->flagForDespawn();
+			$player->getInventory()->sendContents($player);
 		}else{
-			$entity->spawnToAll();
+			$entity->setMotion($entity->getMotion()->multiply($ev->getForce()));
+			if($player->isSurvival()){
+				if(!$infinity){ //TODO: tipped arrows are still consumed when Infinity is applied
+					$player->getInventory()->removeItem(ItemFactory::get(Item::ARROW, 0, 1));
+				}
+				$this->applyDamage(1);
+			}
+
+			if($entity instanceof Projectile){
+				$projectileEv = new ProjectileLaunchEvent($entity);
+				$projectileEv->call();
+				if($projectileEv->isCancelled()){
+					$ev->getProjectile()->flagForDespawn();
+				}else{
+					$ev->getProjectile()->spawnToAll();
+					$player->getLevel()->broadcastLevelSoundEvent($player, LevelSoundEventPacket::SOUND_BOW);
+				}
+			}else{
+				$entity->spawnToAll();
+			}
 		}
 
 		return true;

src/pocketmine/item/Egg.php

@@ -23,6 +23,8 @@ declare(strict_types=1);
 
 namespace pocketmine\item;
 
+use pocketmine\entity\projectile\Egg as EggEntity;
+
 class Egg extends ProjectileItem{
 	public function __construct(){
 		parent::__construct(self::EGG, 0, "Egg");
@@ -32,8 +34,8 @@ class Egg extends ProjectileItem{
 		return 16;
 	}
 
-	public function getProjectileEntityType() : string{
-		return "Egg";
+	public function getProjectileEntityClass() : string{
+		return EggEntity::class;
 	}
 
 	public function getThrowForce() : float{

src/pocketmine/item/EnderPearl.php

@@ -23,6 +23,8 @@ declare(strict_types=1);
 
 namespace pocketmine\item;
 
+use pocketmine\entity\projectile\EnderPearl as EnderPearlEntity;
+
 class EnderPearl extends ProjectileItem{
 	public function __construct(){
 		parent::__construct(self::ENDER_PEARL, 0, "Ender Pearl");
@@ -32,8 +34,8 @@ class EnderPearl extends ProjectileItem{
 		return 16;
 	}
 
-	public function getProjectileEntityType() : string{
-		return "ThrownEnderpearl";
+	public function getProjectileEntityClass() : string{
+		return EnderPearlEntity::class;
 	}
 
 	public function getThrowForce() : float{

src/pocketmine/item/ExperienceBottle.php

@@ -23,13 +23,15 @@ declare(strict_types=1);
 
 namespace pocketmine\item;
 
+use pocketmine\entity\projectile\ExperienceBottle as ExperienceBottleEntity;
+
 class ExperienceBottle extends ProjectileItem{
 	public function __construct(){
 		parent::__construct(self::EXPERIENCE_BOTTLE, 0, "Bottle o' Enchanting");
 	}
 
-	public function getProjectileEntityType() : string{
-		return "ThrownExpBottle";
+	public function getProjectileEntityClass() : string{
+		return ExperienceBottleEntity::class;
 	}
 
 	public function getThrowForce() : float{

src/pocketmine/item/ItemFactory.php

@@ -194,10 +194,10 @@ class ItemFactory{
 		//TODO: ENDER_EYE
 		self::registerItem(new Item(Item::GLISTERING_MELON, 0, "Glistering Melon"));
 
-		foreach(Entity::getKnownEntityTypes() as $className){
-			/** @var Living $className */
+		foreach(Entity::getKnownTypes() as $className){
+			/** @var Living|string $className */
 			if(is_a($className, Living::class, true) and $className::NETWORK_ID !== -1){
-				self::registerItem(new SpawnEgg(Item::SPAWN_EGG, $className::NETWORK_ID, "Spawn Egg"));
+				self::registerItem(new SpawnEgg(Item::SPAWN_EGG, $className::NETWORK_ID, $className, "Spawn Egg"));
 			}
 		}
 

src/pocketmine/item/PaintingItem.php

@@ -93,16 +93,12 @@ class PaintingItem extends Item{
 		$nbt->setInt("TileY", $blockClicked->getFloorY());
 		$nbt->setInt("TileZ", $blockClicked->getFloorZ());
 
-		$entity = Entity::createEntity("Painting", $blockReplace->getLevel(), $nbt);
+		/** @var Painting $entity */
+		$entity = Entity::create(Painting::class, $blockReplace->getLevel(), $nbt);
+		$this->pop();
+		$entity->spawnToAll();
 
-		if($entity instanceof Entity){
-			$this->pop();
-			$entity->spawnToAll();
-
-			$player->getLevel()->broadcastLevelEvent($blockReplace->add(0.5, 0.5, 0.5), LevelEventPacket::EVENT_SOUND_ITEMFRAME_PLACE); //item frame and painting have the same sound
-			return true;
-		}
-
-		return false;
+		$player->getLevel()->broadcastLevelEvent($blockReplace->add(0.5, 0.5, 0.5), LevelEventPacket::EVENT_SOUND_ITEMFRAME_PLACE); //item frame and painting have the same sound
+		return true;
 	}
 }

src/pocketmine/item/ProjectileItem.php

@@ -25,16 +25,22 @@ namespace pocketmine\item;
 
 use pocketmine\entity\Entity;
 use pocketmine\entity\EntityIds;
-use pocketmine\entity\projectile\Projectile;
+use pocketmine\entity\projectile\Throwable;
 use pocketmine\event\entity\ProjectileLaunchEvent;
 use pocketmine\math\Vector3;
 use pocketmine\nbt\tag\CompoundTag;
 use pocketmine\network\mcpe\protocol\LevelSoundEventPacket;
 use pocketmine\Player;
+use pocketmine\utils\Utils;
 
 abstract class ProjectileItem extends Item{
 
-	abstract public function getProjectileEntityType() : string;
+	/**
+	 * Returns the entity type that this projectile creates. This should return a ::class extending Throwable.
+	 *
+	 * @return string class extends Throwable
+	 */
+	abstract public function getProjectileEntityClass() : string;
 
 	abstract public function getThrowForce() : float;
 
@@ -51,29 +57,25 @@ abstract class ProjectileItem extends Item{
 		$nbt = Entity::createBaseNBT($player->add(0, $player->getEyeHeight(), 0), $directionVector, $player->yaw, $player->pitch);
 		$this->addExtraTags($nbt);
 
-		$projectile = Entity::createEntity($this->getProjectileEntityType(), $player->getLevel(), $nbt, $player);
-		if($projectile !== null){
-			$projectile->setMotion($projectile->getMotion()->multiply($this->getThrowForce()));
+		$class = $this->getProjectileEntityClass();
+		Utils::testValidInstance($class, Throwable::class);
+
+		/** @var Throwable $projectile */
+		$projectile = Entity::create($class, $player->getLevel(), $nbt, $player);
+		$projectile->setMotion($projectile->getMotion()->multiply($this->getThrowForce()));
+
+		$projectileEv = new ProjectileLaunchEvent($projectile);
+		$projectileEv->call();
+		if($projectileEv->isCancelled()){
+			$projectile->flagForDespawn();
+		}else{
+			$projectile->spawnToAll();
+
+			$player->getLevel()->broadcastLevelSoundEvent($player, LevelSoundEventPacket::SOUND_THROW, 0, EntityIds::PLAYER);
 		}
 
 		$this->pop();
 
-		if($projectile instanceof Projectile){
-			$projectileEv = new ProjectileLaunchEvent($projectile);
-			$projectileEv->call();
-			if($projectileEv->isCancelled()){
-				$projectile->flagForDespawn();
-			}else{
-				$projectile->spawnToAll();
-
-				$player->getLevel()->broadcastLevelSoundEvent($player, LevelSoundEventPacket::SOUND_THROW, 0, EntityIds::PLAYER);
-			}
-		}elseif($projectile !== null){
-			$projectile->spawnToAll();
-		}else{
-			return false;
-		}
-
 		return true;
 	}
 }

src/pocketmine/item/Snowball.php

@@ -23,6 +23,8 @@ declare(strict_types=1);
 
 namespace pocketmine\item;
 
+use pocketmine\entity\projectile\Snowball as SnowballEntity;
+
 class Snowball extends ProjectileItem{
 	public function __construct(){
 		parent::__construct(self::SNOWBALL, 0, "Snowball");
@@ -32,8 +34,8 @@ class Snowball extends ProjectileItem{
 		return 16;
 	}
 
-	public function getProjectileEntityType() : string{
-		return "Snowball";
+	public function getProjectileEntityClass() : string{
+		return SnowballEntity::class;
 	}
 
 	public function getThrowForce() : float{

src/pocketmine/item/SpawnEgg.php

@@ -27,10 +27,28 @@ use pocketmine\block\Block;
 use pocketmine\entity\Entity;
 use pocketmine\math\Vector3;
 use pocketmine\Player;
+use pocketmine\utils\Utils;
 use function lcg_value;
 
 class SpawnEgg extends Item{
 
+	/** @var string */
+	private $entityClass;
+
+	/**
+	 * @param int    $id
+	 * @param int    $variant
+	 * @param string $entityClass instanceof Entity
+	 * @param string $name
+	 *
+	 * @throws \InvalidArgumentException
+	 */
+	public function __construct(int $id, int $variant, string $entityClass, string $name = "Unknown"){
+		parent::__construct($id, $variant, $name);
+		Utils::testValidInstance($entityClass, Entity::class);
+		$this->entityClass = $entityClass;
+	}
+
 	public function onActivate(Player $player, Block $blockReplace, Block $blockClicked, int $face, Vector3 $clickVector) : bool{
 		$nbt = Entity::createBaseNBT($blockReplace->add(0.5, 0, 0.5), null, lcg_value() * 360, 0);
 
@@ -38,14 +56,9 @@ class SpawnEgg extends Item{
 			$nbt->setString("CustomName", $this->getCustomName());
 		}
 
-		$entity = Entity::createEntity($this->meta, $player->getLevel(), $nbt);
-
-		if($entity instanceof Entity){
-			$this->pop();
-			$entity->spawnToAll();
-			return true;
-		}
-
-		return false;
+		$entity = Entity::create($this->entityClass, $player->getLevel(), $nbt);
+		$this->pop();
+		$entity->spawnToAll();
+		return true;
 	}
 }

src/pocketmine/item/SplashPotion.php

@@ -23,6 +23,7 @@ declare(strict_types=1);
 
 namespace pocketmine\item;
 
+use pocketmine\entity\projectile\SplashPotion as SplashPotionEntity;
 use pocketmine\nbt\tag\CompoundTag;
 
 class SplashPotion extends ProjectileItem{
@@ -35,8 +36,8 @@ class SplashPotion extends ProjectileItem{
 		return 1;
 	}
 
-	public function getProjectileEntityType() : string{
-		return "ThrownPotion";
+	public function getProjectileEntityClass() : string{
+		return SplashPotionEntity::class;
 	}
 
 	public function getThrowForce() : float{