Leave the file cache off when its directory is not writable

OPcache refuses to start, with exit code 254, when it cannot write to
opcache.file_cache. The directory tests are skipped on Windows, which has no
file cache and where ownership and permission bits mean something else.

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>

Author: 2 people

src/Turbo/TurboProcessRestarter.php

@@ -23,6 +23,7 @@
 use function is_dir;
 use function is_link;
 use function is_string;
+use function is_writable;
 use function max;
 use function mkdir;
 use function pcntl_exec;
@@ -416,8 +417,12 @@ public static function isPrivateDirectory(string $directory, int $userId): bool
 		}
 
 		$permissions = @fileperms($directory);
+		if (@fileowner($directory) !== $userId || $permissions === false || ($permissions & 0022) !== 0) {
+			return false;
+		}
 
-		return @fileowner($directory) === $userId && $permissions !== false && ($permissions & 0022) === 0;
+		// OPcache refuses to start at all - exit code 254 - when it cannot write to opcache.file_cache
+		return is_writable($directory);
 	}
 
 	/**

tests/PHPStan/Turbo/TurboProcessRestarterTest.php

@@ -19,6 +19,7 @@
 use function touch;
 use function uniqid;
 use function unlink;
+use const DIRECTORY_SEPARATOR;
 
 final class TurboProcessRestarterTest extends PHPStanTestCase
 {
@@ -173,6 +174,10 @@ public function testResolveContinuousIntegration(array $environment, bool $expec
 
 	public function testIsPrivateDirectory(): void
 	{
+		if (DIRECTORY_SEPARATOR !== '/') {
+			$this->markTestSkipped('There is no file cache on Windows, and its permissions do not map to these checks.');
+		}
+
 		$base = self::createTemporaryDirectory();
 		$userId = (int) fileowner($base);
 
@@ -184,6 +189,10 @@ public function testIsPrivateDirectory(): void
 		chmod($base . '/shared', 0777);
 		$this->assertFalse(TurboProcessRestarter::isPrivateDirectory($base . '/shared', $userId));
 
+		mkdir($base . '/readonly', 0500);
+		$this->assertFalse(TurboProcessRestarter::isPrivateDirectory($base . '/readonly', $userId));
+		chmod($base . '/readonly', 0700);
+
 		symlink($base . '/private', $base . '/link');
 		$this->assertFalse(TurboProcessRestarter::isPrivateDirectory($base . '/link', $userId));
 
@@ -195,6 +204,10 @@ public function testIsPrivateDirectory(): void
 
 	public function testPruneFileCacheDirectories(): void
 	{
+		if (DIRECTORY_SEPARATOR !== '/') {
+			$this->markTestSkipped('There is no file cache on Windows, and the test needs symlinks.');
+		}
+
 		$base = self::createTemporaryDirectory();
 		$now = time();
 		foreach (['current' => 30, 'stale' => 8, 'recent' => 2] as $name => $daysAgo) {