Read ahead: resolve paths before opening connections; a failing readAhead() leaves no spool folder

lib/Backend/StorageBackend.php

@@ -257,6 +257,8 @@ final class StorageBackend implements IBackend, IReadsAhead {
 		if (!$this->sftpReads || $reconnect === null || $ranges === []) {
 			return null;
 		}
+		// before any connection is opened: an invalid path throws
+		$abs = array_map(fn (array $r): array => [$this->abs($r[0]), $r[1], $r[2]], $ranges);
 		$storages = [];
 		$connections = [];
 		$root = '';
@@ -277,7 +279,6 @@ final class StorageBackend implements IBackend, IReadsAhead {
 		if ($connections === []) {
 			return null;
 		}
-		$abs = array_map(fn (array $r): array => [$this->abs($r[0]), $r[1], $r[2]], $ranges);
 		return (static function () use ($storages, $connections, $root, $abs, $spool): \Generator {
 			// the storages hold their connections: kept until the fetcher is done
 			try {

lib/Repository/Repository.php

@@ -254,7 +254,11 @@ final class Repository {
 		if (count($plan->ranges()) < 2 || (!is_dir($plan->spool) && !@mkdir($plan->spool, 0700, true))) {
 			return null;
 		}
-		$streams = $this->backend->readAhead($plan->ranges(), $plan->spool);
+		try {
+			$streams = $this->backend->readAhead($plan->ranges(), $plan->spool);
+		} catch (\Throwable) {
+			$streams = null; // the usual reads report what is wrong
+		}
 		if ($streams === null) {
 			@rmdir($plan->spool);
 			return null;