fix(AmazonS3#getDirectoryMetaData): map root path to filecache key

normalizePath('') returns '.' for S3 object keys, but the filecache stores the
storage root under the key ''. getDirectoryMetaData() was calling getCache()->get('.')
which looks up by md5('.'), never matching the root entry stored at md5('').

The cache miss caused getDirectoryMetaData to return synthetic data with time() as
mtime/storage_mtime and uniqid() as etag on every call. The scanner then saw a
storage_mtime mismatch and wrote the fabricated timestamps back to the cache on every
occ files:scan run, regardless of whether any S3 content had changed.

Introduce getCachePath() to translate the normalized root path '.' back to '' before
any filecache lookup.

Assisted-by: ClaudeCode:claude-sonnet-4-6
Signed-off-by: Maksim Sukharev <antreesy.web@gmail.com>

Author: Antreesy

apps/files_external/lib/Lib/Storage/AmazonS3.php

@@ -70,6 +70,11 @@ private function isRoot(string $path): bool {
 		return $path === '.';
 	}
 
+	private function getCachePath(string $path): string {
+		// normalizePath() converts '' to '.' for S3 object keys, but filecache stores the root as ''
+		return $this->isRoot($path) ? '' : $path;
+	}
+
 	private function cleanKey(string $path): string {
 		if ($this->isRoot($path)) {
 			return '/';
@@ -667,7 +672,7 @@ private function getDirectoryMetaData(string $path): ?array {
 		if ($this->versioningEnabled() && !$this->doesDirectoryExist($path)) {
 			return null;
 		}
-		$cacheEntry = $this->getCache()->get($path);
+		$cacheEntry = $this->getCache()->get($this->getCachePath($path));
 		if ($cacheEntry instanceof CacheEntry) {
 			return $cacheEntry->getData();
 		} else {

apps/files_external/tests/Storage/Amazons3Test.php

@@ -8,6 +8,7 @@
  */
 namespace OCA\Files_External\Tests\Storage;
 
+use OC\Files\Cache\Scanner;
 use OCA\Files_External\Lib\Storage\AmazonS3;
 
 /**
@@ -38,7 +39,29 @@ protected function tearDown(): void {
 		parent::tearDown();
 	}
 
-	public function testStat(): void {
-		$this->markTestSkipped('S3 doesn\'t update the parents folder mtime');
+	/**
+	 * Regression test for the '.' vs '' root path mismatch in getDirectoryMetaData.
+	 *
+	 * normalizePath('') returns '.' for S3 object keys, but the filecache stores the
+	 * storage root under the key ''. Before the fix, getCache()->get('.') returned false,
+	 * causing getDirectoryMetaData to return a fabricated time() on every call, which
+	 * made getCacheEntry always see a changed storage_mtime and fire propagateChange.
+	 */
+	public function testStatRootPreservesStorageMtimeFromCache(): void {
+		$this->instance->getScanner()->scan('', Scanner::SCAN_SHALLOW);
+
+		$cachedRoot = $this->instance->getCache()->get('');
+		$this->assertNotFalse($cachedRoot, 'Root entry must exist in cache after scan');
+
+		$cachedStorageMtime = $cachedRoot['storage_mtime'];
+
+		$stat = $this->instance->stat('');
+		$this->assertNotFalse($stat, 'stat(\'\') must return data');
+		$this->assertEquals(
+			$cachedStorageMtime,
+			$stat['storage_mtime'],
+			'stat(\'\') must return storage_mtime from the cache entry, not a fabricated time()'
+		);
 	}
+
 }