ContainerLoader: make atomic write robust against transient Windows file locks

On Windows, rename() over an existing cached container 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 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. Fixes flaky ContainerLoader.hotReload.

Author: dg

composer.json

@@ -22,7 +22,7 @@
 		"nette/php-generator": "^4.1.6",
 		"nette/robot-loader": "^4.0",
 		"nette/schema": "^1.2.5",
-		"nette/utils": "^4.0"
+		"nette/utils": "^4.0.6"
 	},
 	"require-dev": {
 		"nette/tester": "^2.6",

src/DI/ContainerLoader.php

@@ -8,7 +8,7 @@
 namespace Nette\DI;
 
 use Nette;
-use function class_exists, file_get_contents, file_put_contents, flock, fopen, function_exists, hash, is_file, rename, serialize, sprintf, strlen, substr, unlink, unserialize;
+use function class_exists, file_get_contents, file_put_contents, flock, fopen, function_exists, hash, is_file, rename, serialize, sprintf, strlen, substr, unlink, unserialize, usleep;
 
 
 /**
@@ -74,12 +74,7 @@ private function loadFile(string $class, \Closure $generator): void
 			}
 
 			foreach ($toWrite as $name => $content) {
-				if (file_put_contents("$name.tmp", $content) !== strlen($content) || !rename("$name.tmp", $name)) {
-					@unlink("$name.tmp"); // @ - file may not exist
-					throw new Nette\IOException(sprintf("Unable to create file '%s'.", $name));
-				} elseif (function_exists('opcache_invalidate')) {
-					@opcache_invalidate($name, force: true); // @ can be restricted
-				}
+				$this->atomicWrite($name, $content);
 			}
 		}
 
@@ -90,6 +85,40 @@ private function loadFile(string $class, \Closure $generator): void
 	}
 
 
+	/**
+	 * Atomically writes $content to $file through a temporary file and rename().
+	 *
+	 * On Windows the rename intermittently fails with "Access is denied" when the target is
+	 * momentarily locked (antivirus or a memory-mapped opcache handle); unlike POSIX the replace
+	 * is not atomic against open handles. So the opcache handle is dropped first and the rename
+	 * retried briefly. Elsewhere a single failure throws at once.
+	 */
+	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 Nette\IOException(sprintf("Unable to create file '%s'. %s", $file, Nette\Utils\Helpers::getLastError()));
+		}
+
+		if (function_exists('opcache_invalidate')) {
+			@opcache_invalidate($file, force: true); // @ can be restricted; frees a possible handle on the old target
+		}
+
+		for ($attempt = 1; !@rename($tmp, $file); $attempt++) { // @ is escalated to exception below
+			if ($attempt >= 3 || !Nette\Utils\Helpers::IsWindows) {
+				@unlink($tmp); // @ - file may not exist
+				throw new Nette\IOException(sprintf("Unable to create file '%s'. %s", $file, Nette\Utils\Helpers::getLastError()));
+			}
+			usleep(100_000);
+		}
+
+		if (function_exists('opcache_invalidate')) {
+			@opcache_invalidate($file, force: true); // @ can be restricted; refresh with the new content
+		}
+	}
+
+
 	private function isExpired(string $file, ?string &$updatedMeta = null): bool
 	{
 		if ($this->autoRebuild) {