RobotLoader: make atomic write robust against transient Windows file locks

On Windows, rename() over an existing cache file intermittently fails with
"Access is denied" when the target is momentarily locked by another process
(antivirus scanning the freshly written file, or a memory-mapped opcache handle).
Unlike POSIX, the replace is not atomic against open handles.

Extracts the tmp-write + rename from saveCache() into atomicWrite(), which now
drops the target's opcache handle before renaming and, on Windows only, retries
the rename a few times with a short backoff. On other platforms behavior is
unchanged - a single rename failure still throws immediately.

Author: dg

composer.json

@@ -17,7 +17,7 @@
 	"require": {
 		"php": "8.1 - 8.5",
 		"ext-tokenizer": "*",
-		"nette/utils": "^4.0"
+		"nette/utils": "^4.0.6"
 	},
 	"require-dev": {
 		"nette/tester": "^2.6",

src/RobotLoader/RobotLoader.php

@@ -9,8 +9,9 @@
 
 use Nette;
 use Nette\Utils\FileSystem;
+use Nette\Utils\Helpers;
 use SplFileInfo;
-use function array_merge, defined, extension_loaded, file_get_contents, file_put_contents, filemtime, flock, fopen, function_exists, hash, is_array, is_dir, is_file, realpath, rename, serialize, spl_autoload_register, sprintf, strlen, unlink, var_export;
+use function array_merge, extension_loaded, file_get_contents, file_put_contents, filemtime, flock, fopen, function_exists, hash, is_array, is_dir, is_file, realpath, rename, serialize, spl_autoload_register, sprintf, strlen, unlink, usleep, var_export;
 
 
 /**
@@ -439,7 +440,7 @@ private function loadCache(): void
 		// 1) We want to do as little as possible IO calls on production and also directory and file can be not writable (#19)
 		// so on Linux we include the file directly without shared lock, therefore, the file must be created atomically by renaming.
 		// 2) On Windows file cannot be renamed-to while is open (ie by include() #11), so we have to acquire a lock.
-		$lock = defined('PHP_WINDOWS_VERSION_BUILD')
+		$lock = Helpers::IsWindows
 			? $this->acquireLock("$file.lock", LOCK_SH)
 			: null;
 
@@ -482,14 +483,36 @@ private function saveCache($lock = null): void
 		$file = $this->generateCacheFileName();
 		$lock = $lock ?: $this->acquireLock("$file.lock", LOCK_EX);
 		$code = "<?php\nreturn " . var_export([$this->classes, $this->missingClasses, $this->emptyFiles], return: true) . ";\n";
+		$this->atomicWrite($file, $code);
+	}
+
 
-		if (file_put_contents("$file.tmp", $code) !== strlen($code) || !rename("$file.tmp", $file)) {
-			@unlink("$file.tmp"); // @ file may not exist
-			throw new \RuntimeException(sprintf("Unable to create '%s'.", $file));
+	/**
+	 * Atomically writes $content to $file via a temporary file and rename().
+	 * On Windows rename() over a momentarily locked target intermittently fails, so it is retried briefly.
+	 */
+	private function atomicWrite(string $file, string $content): void
+	{
+		$tmp = "$file.tmp";
+		if (file_put_contents($tmp, $content) !== strlen($content)) {
+			@unlink($tmp); // @ - file may not exist
+			throw new \RuntimeException(sprintf("Unable to create '%s'. %s", $file, Helpers::getLastError()));
+		}
+
+		if (function_exists('opcache_invalidate')) {
+			@opcache_invalidate($file, force: true); // @ - can be restricted
+		}
+
+		for ($attempt = 1; !@rename($tmp, $file); $attempt++) {
+			if ($attempt >= 3 || !Helpers::IsWindows) {
+				@unlink($tmp);
+				throw new \RuntimeException(sprintf("Unable to create '%s'. %s", $file, Helpers::getLastError()));
+			}
+			usleep(100_000);
 		}
 
 		if (function_exists('opcache_invalidate')) {
-			@opcache_invalidate($file, force: true); // @ can be restricted
+			@opcache_invalidate($file, force: true); // @ - can be restricted
 		}
 	}