* * @internal */ final class ServiceLoaderIterator implements Iterator { /** @var class-string */ private readonly string $service; /** @var list */ private readonly array $providers; /** @var array */ private array $cache; /** @var int<0, max> */ private int $index = 0; /** * @param class-string $service * @param list $providers * @param array $cache */ public function __construct(string $service, array $providers, array &$cache) { $this->service = $service; $this->providers = $providers; $this->cache = &$cache; } public function current(): ?object { $index = $this->index; if ($instance = $this->cache[$index] ?? null) { return $instance; } if (($class = $this->providers[$index] ?? null) === null) { return null; } $this->cache[$index] = false; if (!is_subclass_of($class, $this->service)) { throw new ServiceConfigurationError(sprintf( 'Invalid service provider, expected implementation of "%s", got "%s"', $this->service, $class, )); } try { return $this->cache[$index] = new $class(); } catch (Throwable $e) { throw new ServiceConfigurationError(sprintf( 'Invalid service provider, failed to instantiate "%s" provider "%s": %s', $this->service, $class, $e->getMessage(), ), previous: $e); } } public function next(): void { $this->index++; $this->skipInvalid(); } public function key(): ?string { return $this->providers[$this->index] ?? null; } public function valid(): bool { return $this->index < count($this->providers); } public function rewind(): void { $this->index = 0; $this->skipInvalid(); } private function skipInvalid(): void { while (($this->cache[$this->index] ?? null) === false) { $this->index++; } } }