Entity: do not assume that save IDs are always strings

this is only the first of many changes needed to make entity savedata fully format-agnostic, but it's a start.

src/entity/Entity.php

@@ -473,7 +473,7 @@ abstract class Entity{
 		$nbt = EntityDataHelper::createBaseNBT($this->location, $this->motion, $this->location->yaw, $this->location->pitch);
 
 		if(!($this instanceof Player)){
-			$nbt->setString("id", EntityFactory::getInstance()->getSaveId(get_class($this)));
+			EntityFactory::getInstance()->injectSaveId(get_class($this), $nbt);
 
 			if($this->getNameTag() !== ""){
 				$nbt->setString("CustomName", $this->getNameTag());

src/entity/EntityFactory.php

@@ -227,6 +227,14 @@ final class EntityFactory{
 		return $entity;
 	}
 
+	public function injectSaveId(string $class, CompoundTag $saveData) : void{
+		if(isset($this->saveNames[$class])){
+			$saveData->setTag("id", new StringTag(reset($this->saveNames[$class])));
+		}else{
+			throw new \InvalidArgumentException("Entity $class is not registered");
+		}
+	}
+
 	/**
 	 * @phpstan-param class-string<Entity> $class
 	 */

tests/phpstan/configs/l7-baseline.neon

@@ -530,6 +530,11 @@ parameters:
 			count: 1
 			path: ../../../src/data/bedrock/LegacyToStringBidirectionalIdMap.php
 
+		-
+			message: "#^Parameter \\#1 \\$value of class pocketmine\\\\nbt\\\\tag\\\\StringTag constructor expects string, string\\|false given\\.$#"
+			count: 1
+			path: ../../../src/entity/EntityFactory.php
+
 		-
 			message: "#^Method pocketmine\\\\entity\\\\EntityFactory\\:\\:getSaveId\\(\\) should return string but returns string\\|false\\.$#"
 			count: 1