GeneratorManager::getGenerator() now returns null for unknown generator aliases

instead of returning Normal::class (indistinguishable from successful match) or throwing an exception (pain in the ass to handle).

src/Server.php

@@ -106,6 +106,7 @@ use pocketmine\world\format\io\WorldProviderManager;
 use pocketmine\world\format\io\WritableWorldProviderManagerEntry;
 use pocketmine\world\generator\Generator;
 use pocketmine\world\generator\GeneratorManager;
+use pocketmine\world\generator\normal\Normal;
 use pocketmine\world\World;
 use pocketmine\world\WorldCreationOptions;
 use pocketmine\world\WorldManager;
@@ -979,7 +980,7 @@ class Server{
 
 					if(isset($options["generator"])){
 						$generatorOptions = explode(":", $options["generator"]);
-						$creationOptions->setGeneratorClass(GeneratorManager::getInstance()->getGenerator(array_shift($generatorOptions)));
+						$creationOptions->setGeneratorClass(GeneratorManager::getInstance()->getGenerator(array_shift($generatorOptions)) ?? Normal::class);
 						if(count($generatorOptions) > 0){
 							$creationOptions->setGeneratorOptions(implode(":", $generatorOptions));
 						}
@@ -1010,7 +1011,7 @@ class Server{
 				}
 				if(!$this->worldManager->loadWorld($default, true)){
 					$creationOptions = WorldCreationOptions::create()
-						->setGeneratorClass(GeneratorManager::getInstance()->getGenerator($this->configGroup->getConfigString("level-type")))
+						->setGeneratorClass(GeneratorManager::getInstance()->getGenerator($this->configGroup->getConfigString("level-type")) ?? Normal::class)
 						->setGeneratorOptions($this->configGroup->getConfigString("generator-settings"));
 					$convertedSeed = Generator::convertSeed($this->configGroup->getConfigString("level-seed"));
 					if($convertedSeed !== null){

src/world/World.php

@@ -411,7 +411,8 @@ class World implements ChunkManager{
 		$this->maxY = $this->provider->getWorldMaxY();
 
 		$this->server->getLogger()->info($this->server->getLanguage()->translate(KnownTranslationFactory::pocketmine_level_preparing($this->displayName)));
-		$this->generator = GeneratorManager::getInstance()->getGenerator($this->provider->getWorldData()->getGenerator(), true);
+		$this->generator = GeneratorManager::getInstance()->getGenerator($this->provider->getWorldData()->getGenerator()) ??
+			throw new AssumptionFailedError("WorldManager should already have checked that the generator exists");
 		//TODO: validate generator options
 		$this->chunkPopulationRequestQueue = new \SplQueue();
 		$this->addOnUnloadCallback(function() : void{

src/world/WorldManager.php

@@ -220,9 +220,8 @@ class WorldManager{
 			)));
 			return false;
 		}
-		try{
+
-			GeneratorManager::getInstance()->getGenerator($provider->getWorldData()->getGenerator(), true);
+		if(GeneratorManager::getInstance()->getGenerator($provider->getWorldData()->getGenerator()) === null){
-		}catch(\InvalidArgumentException $e){
 			$this->server->getLogger()->error($this->server->getLanguage()->translate(KnownTranslationFactory::pocketmine_level_loadError(
 				$name,
 				KnownTranslationFactory::pocketmine_level_unknownGenerator($provider->getWorldData()->getGenerator())

src/world/format/io/FormatConverter.php

@@ -25,6 +25,7 @@ namespace pocketmine\world\format\io;
 
 use pocketmine\utils\Filesystem;
 use pocketmine\world\generator\GeneratorManager;
+use pocketmine\world\generator\normal\Normal;
 use pocketmine\world\WorldCreationOptions;
 use Webmozart\PathUtil\Path;
 use function basename;
@@ -112,7 +113,9 @@ class FormatConverter{
 			Filesystem::recursiveUnlink($convertedOutput);
 		}
 		$this->newProvider->generate($convertedOutput, $data->getName(), WorldCreationOptions::create()
-			->setGeneratorClass(GeneratorManager::getInstance()->getGenerator($data->getGenerator()))
+			//TODO: defaulting to NORMAL here really isn't very good behaviour, but it's consistent with what we already
+			//did previously; besides, WorldManager checks for unknown generators before this is reached anyway.
+			->setGeneratorClass(GeneratorManager::getInstance()->getGenerator($data->getGenerator()) ?? Normal::class)
 			->setGeneratorOptions($data->getGeneratorOptions())
 			->setSeed($data->getSeed())
 			->setSpawnPosition($data->getSpawn())

src/world/generator/GeneratorManager.php

@@ -79,20 +79,11 @@ final class GeneratorManager{
 	 *
 	 * @param bool   $throwOnMissing @deprecated this is for backwards compatibility only
 	 *
-	 * @return string Name of class that extends Generator
+	 * @return string|null Name of class that extends Generator, or null if no generator is mapped to that name
-	 * @phpstan-return class-string<Generator>
+	 * @phpstan-return class-string<Generator>|null
-	 *
-	 * @throws \InvalidArgumentException if the generator type isn't registered
 	 */
-	public function getGenerator(string $name, bool $throwOnMissing = false){
+	public function getGenerator(string $name, bool $throwOnMissing = false) : ?string{
-		if(isset($this->list[$name = strtolower($name)])){
+		return $this->list[strtolower($name)] ?? null;
-			return $this->list[$name];
-		}
-
-		if($throwOnMissing){
-			throw new \InvalidArgumentException("Alias \"$name\" does not map to any known generator");
-		}
-		return Normal::class;
 	}
 
 	/**